Patent Document

RELATED APPLICATIONS 
     This application claims priority to German Patent Application No. DE 10 2008 062 450.0, filed Dec. 13, 2008, which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The invention is directed to an arrangement for the illumination of a substrate with a plurality of individually shaped, controllable particle beams with a particle beam source for emitting a particle beam, an illumination system for shaping and deflecting the particle beam for the illumination of a first aperture diaphragm array, wherein the aperture diaphragm array is a multiple-format diaphragm array for generating separate particle beamlets, a second multiple-format diaphragm array on which the first multiple-format diaphragm array is imaged by means of a condenser lens system and which has diaphragm apertures that are adapted to the first multiple-diaphragm array while taking into account the imaging scale, a multibeam deflector system for individual beam deflection of the separate particle beams, and reduction optics having at least one stage for reduced imaging of the particle beamlets passed by the second aperture diaphragm array onto a substrate. The invention is preferably applied in electron beam lithography, particularly in the semiconductor industry, for direct structuring of wafers and masks for photolithography. 
     BACKGROUND OF THE INVENTION 
     With each technology node, that is, about every three years, there is a doubling of the quantity of structures on a component surface of the same size. Therefore, the image-generating methods for producing structures on masks and methods for direct structuring of wafers require increasingly longer writing times. Another reason for reduced productivity in high-resolution electron beam writers in high-end mask fabrication is the increasing degree of pre-distortion of the mask structure (optical proximity correction—OPC) to improve the structure resolution of high-productivity scanner objectives whose resolution, as is well-known, is diffraction-limited. 
     The demand in the semiconductor industry for lowering costs by reducing writing times in high-end mask fabrication and in direct exposure of wafers cannot be met by currently available single-beam writing technologies. 
     For this reason, alternative multibeam concepts are being adopted to an increasing extent. Multi-shape beam lithography concepts promise an appreciable increase in throughput especially for very high integration levels (&lt;65 nm technology). The concept is based on the idea of simultaneously providing a plurality of particle beams whose shape and size can be adjusted and whose position on the substrate can be controlled. Two main methods for increasing throughput in particle beam lithography systems are known from the prior art. 
     On one side are the solutions for multibeam systems which work closely in parallel and use large arrays (10 4 -10 7  beams) of finely focused particle beam bundles of fixed shape and size (electron beam pixels) which are guided substantially collectively over the substrate to be exposed (stage movement and deflection systems) and which are timed to be switched on and off corresponding to the pattern to be exposed. This pixel concept is represented, e.g., by MAPPER (see C. Klein et al., “Projection maskless lithography (PML2): proof-of-concept setup and first experimental results”, Proceedings SPIE Advanced Lithography 2008, vol. 6921-93), and PML2 (see E. Slot et al., “MAPPER: high throughput maskless lithography”, Proceedings SPIE Advanced Lithography 2008, vol. 6921-92). The disadvantages of these concepts are the high complexity of the beam modulators (thousands to hundreds of thousands of deflection systems/lenses) and the high data transfer rates owing to the fact that the circuit layout must be broken down into individual pixels without losses so that any hierarchy or compression is lost. 
     The second group of solutions is based on variably shaped beams (also known as shaped probes) which are used to expose desired structures in a variable manner by projecting beam cross sections of different area on a substrate (VSB—variable shaped beam). 
     U.S. Pat. No. 6,703,629 B2 discloses a fairly complex character projection (CP) method in which different masks are imaged one above the other in two planes, and possibly deflected by a deflection system located therebetween, in such a way that typical recurring beam patterns are formed and are then reduced and used for exposure. The drawbacks of this method consist in the fixed choice of character aperture geometry once it has been produced. Another level of technology requiring different conductive path distances or CP dimensions requires a new pair of character apertures. Another disadvantage of this exposure method consists in that, for reasons inherent to the principle, the current density within a character is constant. Accordingly, a correction of the proximity effect depending on the exposure environment, particularly for a large character, is difficult to accomplish, which limits the usefulness and quality of the generated patterns. 
     It is known from U.S. Pat. No. 7,005,658 B2 to generate an array of particle beams by means of an aperture plate which is illuminated in parallel in that a shared radiation source is collimated by means of a condenser lens. All of the partial beams are corrected individually by correction lenses and deflection systems in such a way that the field distortion and field curvature occurring in the reduction system disappear. The array of spot beams generated in this way is then guided collectively over the substrate to be exposed, and the partial beams are switched on and off (blanking array) at the proper times corresponding to the desired pattern. 
     A disadvantage in this method is the large amount of pixel data required for exposing a given pattern. Further, a large number of complicated electrostatic correction elements such as lens arrays and deflection arrays are required for controlling the positions and focus planes of all of the partial beams in the target. Another disadvantage in this method is that the individual beams in the target plane have the same size and are located on a fixed position grid. In order to meet current requirements for positioning accuracy of patterns to be exposed (placement 2-5 nm), multiple exposures must be carried out with a slight positional offset (so-called grayscale exposure or gray beaming) which, as is well known, results in a deterioration of structure edges and reduces productivity. 
     U.S. Pat. No. 5,981,962 A and U.S. Pat. No. 6,175,122 B1 describe an electron beam lithography system as a distributed arrangement of multiple variable shaped beams working in parallel. The concept, which is conceived as a compact miniature system, uses two pinhole diaphragms per electron-optical system which are imaged on one another and a deflection system arranged therebetween for controlling the beam cross section. An external, uniform magnetic field provides for the focused imaging of the diaphragm planes on one another and on the target. It is suggested that the position deflection in the target is carried out by moving the substrate stage in one direction and by collective, line-by-line electrostatic deflection in orthogonal direction. Every miniaturized VSB system (variable shaped beam system) is supplied by separate electron sources (emitter arrays). 
     A disadvantage in this method is the 1:1 imaging of the beam-shaping diaphragms in the target plane. The required edge roughness of lithographic structures is presently in the range of a few nanometers for advanced technologies. Accordingly, the quality of the diaphragms to be used would have to be even better, which appears very difficult in terms of technology, particularly with respect to the generation of such small corner radii. Contamination effects at the diaphragm edges in practical operation are likewise effective in a ratio of 1:1 during exposure and therefore limit the quality of the patterns and the life of the diaphragms. Further, the resources required for providing an entire array of radiation sources and for monitoring them individually is disadvantageous. A very high mechanical accuracy and high uniformity of the magnetic field is required in order to maintain the focusing condition simultaneously for all beam bundles, which can only be achieved at great expense. 
     Further, it remains unclear how collective focusing is to be carried out when the target (e.g., machined wafer) has inevitable residual unevenness. Finally, the collective deflection of all of the beams in the target plane presents a severe limitation on the quantity of beams that can be used simultaneously for exposure or defines a fixed grid for pattern generation. The fixed grid of the beam bundles must constantly be aligned with the necessary reference positions of the patterns to be exposed. In the case of very precise draft grids of the patterns, this substantially limits productivity and/or flexibility of the exposure device. 
     U.S. Pat. No. 6,614,035 B2 describes a multibeam system whose operation is very similar to that of the known VSB system (single beam). In order to separate a plurality of individually controllable beams in the area of the two beam-shaping diaphragm planes, it is suggested that a diaphragm is arranged at that location which subdivides the conventional illuminated area (diaphragm aperture) by inserting struts into a plurality of openings. Every beam bundle formed in this manner receives four individual deflection systems which are arranged in two portions of the electron-optical column and carry out two independent functions. The upper, first deflection system stage serves to individually adjust the beam cross section and the second defecting system stage serves to adjust the distance between adjacent beam bundles within certain limits. The subsequent reduction and positioning of the array of beam bundles in the lower imaging portion is carried out collectively and in exactly the same way as in a VSB system. 
     This concept has the disadvantage that the deflection of the beam bundles in two orthogonal directions is carried out in only one plane because, in deflection arrangements with such close proximity of the beams, simultaneous deflection in two orthogonal directions leads to large deflection errors which impair the edge quality and uniformity of the illumination. This also applies to deflection systems for individual control of the mutual beam distance in an array of partial beams that are to be controlled individually. Further, there are no concrete proposals for preventing crosstalk between the adjacent deflection systems which are arranged within a very confined space in proximity to the beam for every beam of the multibeam system. 
     Another weakness in the concept is the use of a plurality of small variable beam cross sections of comparable size for the exposure process of an entire design layout. Typically, the layout to be exposed does not contain exclusively very small structures even at an advanced level of integration, but rather also larger structures. The gain in productivity which is achieved when exposing many small structures by means of an array of 4 to 16 beams working in parallel can be partially negated when the layout contains a series of relatively large patterns with unfavorable spacing. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to find a novel possibility for illuminating a substrate with a plurality of individually shaped, controllable particle beams which permits a high-resolution structuring of substrates with a high substrate throughput without limiting the flexibility of the structure patterns to be illuminated or sacrificing a high substrate throughput for a high flexibility of structure patterns to be illuminated. 
     In an arrangement for the illumination of a substrate with a plurality of individually shaped, controllable particle beams with a particle beam source for emitting a particle beam, an illumination system for shaping and deflecting the particle beam for the illumination of a first aperture diaphragm array, wherein the aperture diaphragm array is a multiple-diaphragm array for generating separate particle beamlets, a second multiple-diaphragm array on which the first multiple-diaphragm array is imaged by means of a condenser lens system and which has diaphragm apertures which are adapted to the first multiple-diaphragm array while taking into account the imaging scale, a multibeam deflector system for individual beam deflection of the separate particle beams, and reduction optics having at least one stage for reduced imaging of the particle beamlets passed by the second aperture diaphragm array onto a substrate, the above-stated object is met according to the invention in that the first multiple-diaphragm array and the second multiple-diaphragm array are constructed as multiple-format diaphragm arrays for generating particle beamlets with different beam cross sections, in that at least three multibeam deflector arrays for individual deflection of the particle beamlets are associated with the first multiple-format diaphragm array and with the second multiple-format diaphragm array, wherein at least a first multibeam deflector array is arranged between the first multiple-format diaphragm array and the second multiple-format diaphragm array in order to generate different cross sections of the particle beamlets after the second multiple-format diaphragm array by means of an individual beam deflection of the individual particle beamlets, at least a second multibeam deflector array is arranged in the vicinity of the second multiple-format diaphragm array in order to individually deflect partial crossovers of the individual particle beamlets or to deliberately blank individual particle beamlets at an exit aperture diaphragm arranged in a crossover downstream, and at least a third multibeam deflector array is arranged downstream of the second multiple-format diaphragm array at a distance of 10-20% of the distance between the multiple-format diaphragm array and the crossover in order to generate different positions of the particle beamlets on the substrate. 
     The multibeam deflector arrays are advantageously composed of two deflector chips which are arranged one on top of the other and on each of which is provided a deflector cell array comprising identical pairs of electrodes for the individual deflection of individual particle beamlets in the same direction lateral to the optical axis, wherein the pairs of electrodes of the deflector cell arrays on the two deflector chips are oriented in substantially orthogonal directions relative to one another. 
     In a preferred embodiment form, an illumination group selector with a stigmator arranged downstream is arranged in the beam path of the illumination system for the particle beam emitted by the particle beam source for selecting an illumination group on the first multiple-format diaphragm array. 
     The multiple-format diaphragm arrays advantageously have at least two large diaphragm apertures with an edge length in the range of 30 μm to 200 μm for exposure with large-format particle beamlet and at least one beam-shaping diaphragm group comprising a plurality of small diaphragm apertures with an edge length in the range of 5 μm to 20 μm for exposure with an array of small-format particle beamlets. 
     The multiple-format diaphragm arrays can advisably have different beam-shaping diaphragm groups, wherein one of a plurality of different beam-shaping diaphragm groups of the first multiple-format diaphragm array can be illuminated separately by means of the illumination group selector of the illumination system in order to generate differently dimensioned particle beamlets and arrays of particle beamlets. 
     In a first variant, the multibeam deflector arrays for individual deflection of the particle beamlets are preferably arranged in such a way that the first multibeam deflector array is arranged behind the first multiple-format diaphragm array, the second multibeam deflector array is arranged in front of the second multiple-format diaphragm array, and the third multibeam deflector array is arranged behind the second multiple-format diaphragm array. 
     In a second variant, the first multibeam deflector array can be arranged in front of the second multiple-format diaphragm array, and the second multibeam deflector array and third multibeam deflector array are arranged behind the second multiple-format diaphragm array. 
     In a third embodiment form, the first multibeam deflector array is arranged behind and in the immediate vicinity of the first multiple-format diaphragm array, the second multibeam deflector array is arranged in front of and in the immediate vicinity of the second multiple-format diaphragm array, and the third multibeam deflector array is arranged behind the second multiple-format diaphragm array at a distance equal to 10% to 20% of the distance to the next crossover. 
     In a fourth variant, the first multibeam deflector array can be arranged in front of and in the immediate vicinity of the second multiple-format diaphragm array, the second multibeam deflector array can be arranged behind and in the immediate vicinity of the second multiple-format diaphragm array, and the third multibeam deflector array can be arranged behind the second multiple-format diaphragm array at a distance equal to 10% to 20% of the distance to the next crossover. 
     In a fifth advantageous variant, the first multibeam deflector array is arranged behind and in the immediate vicinity of the first multiple-format diaphragm array, the second multibeam deflector array is arranged behind and in the immediate vicinity of the second multiple-format diaphragm array, and the third multibeam deflector array is arranged behind the second multiple-format diaphragm array at a distance equal to 10% to 20% of the distance to the next crossover. 
     In a sixth variant, the first multibeam deflector array is arranged behind and in the immediate vicinity of the first multiple-format diaphragm array, the second multibeam deflector array is arranged in front of and in the immediate vicinity of the second multiple-format diaphragm array, the third multibeam deflector array, as a first precision positioning array, is arranged behind and in the immediate vicinity of the second multiple-format diaphragm array, and a fourth multibeam deflector array, as second precision positioning array, is arranged behind the third multibeam deflector array. 
     In all of the variants mentioned above, a stigmator having at least two stages is advisably arranged between the third multibeam deflector array and the reduction system imaging on the substrate in order to correct for tolerance-dependent distortion. 
     It has proven advantageous to arrange the pairs of electrodes of the deflector cell array of every multibeam deflector array orthogonal to one another on the deflector chips located one on top of the other. 
     Further, when a beam-shaping diaphragm group is used in an array with a format (n×m), the multibeam deflector arrays advisably have a deflector cell array with at least (n+2) rows and (m+2) columns of deflector cells of parallel electrode pairs on every deflector chip, and no voltage is applied to the outside deflector cells. 
     To compensate for crosstalk between adjacent deflector cells of the deflector cell array, means for calculating voltage and regulating voltage are advantageously provided in which exclusively the crosstalk effect of the respective eight directly adjacent deflector cells is taken into account for each particle beamlet considered individually in order to calculate the correction of the deflection voltages within a deflector cell array. 
     In this connection, the multibeam deflector arrays preferably have fast pipeline structures comprising multi-channel active components for fast independent control of the beam position, cross-sectional area, and individual crossover position for each particle beamlet, wherein the pipeline structures advisably contain multi-DA converters, demultiplexers, and multi-operational amplifiers. 
     It has proven advisable to provide a coupling matrix for controlling all of the multibeam deflector arrays in order to achieve an independent control of the position and size of the particle beamlet on the substrate and of the individual crossover position for each particle beamlet of an array of particle beamlets in the X-direction and Y-direction. 
     To increase the flexibility of the exposable structure patterns, at least the second multiple-format diaphragm array has, in addition, special characters (structure patterns) for exposing repetitive structures. 
     Further, it is advisable when the multiple-format diaphragm arrays have a plurality of different beam-shaping diaphragm groups with identical diaphragm apertures or a plurality of beam-shaping diaphragm groups with different diaphragm apertures. 
     To minimize the quantity of individual exposure steps on the substrate, a pre-programmable control unit is advisably provided for controlling the illumination group selector with stigmators arranged downstream in order to optimize the selection of illumination groups on the first multiple-format diaphragm array. 
     The basic idea behind the invention is the known concept of variable shaped beams (VSB concept) which, as a single beam concept, makes it possible to combine a relatively large maximum area of the beam cross section with an array of variably controllable shaped beams with small beamlet areas. In the course of exposing a substrate, fast deflecting processes can be used to switch between these beam modulation variants electron-optically. Further, steps which succeed in minimizing the crosstalk between the electrostatic deflection systems which are provided separately for each particle beamlet are described for the deflection of the variable, finely-structured shaped beams. 
     The inventive solution makes it possible to realize an illumination of a substrate with particle radiation which permits a high-resolution structuring of substrates with a high substrate throughput without limiting the flexibility of the structure patterns to be illuminated or sacrificing substrate throughput for a flexibility of the structure patterns that can be illuminated. 
     The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings: 
         FIG. 1  shows a schematic diagram of the arrangement according to the invention, showing selected particle beamlets; 
         FIG. 2  shows an embodiment form of the invention with an arrangement of the multibeam deflector arrays for the particle beamlets, all in the vicinity of the second multiple-format diaphragm array; 
         FIG. 3  shows a constructional variant of combined multiple-format diaphragm arrays and multibeam deflector arrays with control electronics on a printed circuit board ( FIG. 3   a ) and a sectional view of a twofold arrangement for separate deflecting directions in x and y ( FIG. 3   b ); 
         FIG. 4  shows an embodiment form of the first multiple-format diaphragm array ( FIG. 4   a ) and of the second multiple-format diaphragm array ( FIG. 4   b ) with the associated multibeam deflector arrays; 
         FIG. 5  shows a section from  FIG. 4   a  showing a multibeam deflector array with an electrode structure for suppressing crosstalk; 
         FIG. 6  shows a flow chart showing the data provided for controlling a multibeam deflector array according to  FIGS. 3   a  and  3   b;    
         FIG. 7  shows basic embodiment forms of the first multiple-format diaphragm array ( FIG. 7   a ) and second multiple-format diaphragm array ( FIG. 7   b ); 
         FIG. 8  shows another embodiment form of an electron beam lithography device with parallel orientation of the particle beam in front of the first multiple-format diaphragm array and a multibeam deflector array following the first and second multibeam deflector arrays in front of and behind the second multiple-format diaphragm array; and 
         FIG. 9  shows an embodiment form of an electron beam lithography device with telecentric illumination as in  FIG. 8  and four multibeam deflector arrays, wherein one multibeam deflector array is arranged after the first multiple-format diaphragm array, one multibeam deflector array is arranged in front of the second multiple-format diaphragm array, and two multibeam deflector arrays are arranged after the second multiple-format diaphragm array. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As is shown schematically in  FIG. 1 , the arrangement for substrate illumination with a plurality of individual particle beams basically comprises a particle beam source  1  defining an optical axis  115  along which the entire particle beam column up to the substrate  91  has the following components: an illumination system  2  for illuminating a first multiple-format diaphragm array  41  in selectable illumination groups, a beam modulator system  3  for generating a plurality of particle beamlets  118  containing, in addition to a condenser system  31 - 32 , a group deflection system  35  and a multideflector system  5  cooperating with a multi-aperture diaphragm system  4  for individual deflection and shaping of the individual particle beamlets  118 . Following the latter is a reduction system  6  for imaging the particle beamlets  118  transmitted by the multi-aperture diaphragm system  4  onto the substrate  91  moving on a substrate stage  9 . A substrate monitoring sensor arrangement  8  is provided directly above the substrate stage  9  for observing the structure patterns which are exposed on the substrate  91  by means of the particle beamlets  118 . 
     The generation of an array of variably controllable particle beamlets  118  within the beam modulator system  3  is characterized in that a first multiple-format diaphragm array  41  and a second multiple-format diaphragm array  42  are arranged in two diaphragm planes and are outfitted in each instance with equivalent beam-shaping diaphragm groups  45  comprising arrays of small openings (5 to 20 μm) associated with one another and, optionally, additional larger openings (30 to 200 μm). The first multiple-format diaphragm array  41  is imaged on the second multiple-format diaphragm array  42  by a condenser system  31 - 32  (preferably in a scale of 1:1). 
     On their path through the condenser system  31 - 32  to the second multiple-format diaphragm array  42 , the particle beamlets  118  pass through at least one group deflection system  35  and at least one multibeam deflector array  51  and  52  of the multideflector system  5  in addition to the condenser system  31 - 32 . 
     When the first multiple-format diaphragm array  41  is illuminated by an illumination group  117  installed in the illumination system  2  in the region of a beam-shaping diaphragm group  45  (see  FIG. 7   a ), an array of particle beamlets  118  is generated and passes through the condenser system  31 - 32  and the collective group deflection system  35  on its path toward the second multiple-format diaphragm array  42 . An individual displacement (deflection) of every particle beamlet  118  lateral to the beam direction by means of deflection can be carried out by individually controllable electric fields in two coordinate directions within each of the multibeam deflector arrays  51  and  52 . 
     The multibeam deflector arrays  51  and  52  are advisably arranged in the vicinity of one of the multiple-format diaphragm arrays  41  and/or  42 . Following this at a distance of 10% to 20% of the distance to the next crossover  112  is the third multibeam deflector array  35  which serves as a precision positioning system for the individual positioning of the individual particle beamlets  118  on the substrate  9 . In this connection, it is necessary that at least one multibeam deflector array  51  is situated between the two multiple-format diaphragm arrays  41  and  42 . This multibeam deflector array  51  can be arranged optionally in the vicinity of either the first multiple-format diaphragm array  41  or the second multiple-format diaphragm array  42 . 
     The positioning of a multibeam deflector array  51  and  52 , respectively, shown in  FIG. 1 , in the vicinity of the multiple-format diaphragm arrays  41  and  42  can accordingly also be modified in such a way that both of the multibeam deflector arrays  51  and  52  are arranged in the vicinity of the second multiple-format diaphragm array  42 , i.e., one in front of it and the other behind it. 
     In every case, a cropping of each particle beamlet  118  accordingly takes place at the location of the second multiple-format diaphragm array  41  depending on its actual individual displacement through the at least one multibeam deflector array  51  located between the multiple-format diaphragm arrays  41  and  42 . 
     The use of the specially structured multibeam deflector arrays  51  and  52 , whose specific construction is shown in  FIGS. 3   a ,  4   a ,  4   b  and  5 , makes possible an additional individual position control of every particle beamlet  118  in the crossover  111  inside the array of the particle beamlets  118 , namely, regardless of their individual format size (beam cross section). The at least one multibeam deflector array  51  downstream of the second multiple-format diaphragm array  42  is responsible for this. A precision correction of the beam positions in the crossover  112  is carried out by another identically constructed multibeam deflector array  53  arranged downstream. 
     The multi-stage group deflection system  35  in the area of the condenser system  31 - 32  serves to control particle beamlets  118  formed as a result of the selection of an illumination group  117  in the region of larger diaphragm apertures  44  (30 to 200 μm edge dimension) of the multiple-format diaphragm array  41  (see  FIG. 7   a ). By outfitting the diaphragm plates  43  of the multiple-format diaphragm arrays  41  and  42  with large-format diaphragm apertures  44  (30 to 200 μm) in addition to the small-format (5 to 20 μm) diaphragm apertures  44 , larger illumination surfaces can also be realized on the substrate  91  with the same exposure arrangement in order to expose large-area patterns on the substrate  91  in a time-saving manner. 
       FIG. 1  shows a first embodiment form of the invention in which the illumination is carried out—for the sake of simplicity—by means of an individual particle beam source  1  which comprises an adapting condenser  21 , an illumination group selector  22  having a beam deflection system for deflecting the particle beam  11  from the optical axis  115 , and a stigmator  23 . The function of the condenser  21  of the illumination system  2  is to image the beam output diaphragm  116  of the particle beam source  1  on a first multiple-format diaphragm array  41  and to generate a first intermediate image of the beam output  10  of the particle beam source  1  in the crossover  110 . 
     Depending on a structure pattern to be generated on the substrate  91 , an illumination group  117  for selective illumination of a diaphragm aperture  44  which is shaped in a definite manner or a beam-shaping diaphragm group  45  of the first multiple-format diaphragm array  41  is automatically selected and controlled in the illumination system  2  of the particle beam column which is characterized by a linear optical axis  115  from the beam outlet of the particle beam source  1  to the target on the substrate  91  to be exposed. This selection of the beam-shaping diaphragms is carried out by means of a suitable deflection of the particle beam  11  by means of the illumination group selector  22 . 
     When using a first multiple-format diaphragm array  41  according to  FIG. 7   a , individual large variably shaped particle beams can be selected through large diaphragm apertures  44  and an array of smaller variable particle beamlets  118  can be selected through the beam-shaping diaphragm group  45 . Further, when using a second multiple-format diaphragm array  42  according to  FIG. 7   b  in which the diaphragm plate  43  does not have the same diaphragm apertures  44  as the first multiple-format diaphragm array  41 , other beam shape variants such as, e.g., rhombuses, triangles, etc. (principle of generation according to DD 241 500 A1) or special characters  46  ( FIG. 7   b ) can also be generated as is described more fully referring to  FIG. 7   b.    
     Other variants for beam shaping of an individual particle beam cross section having a relatively large variable area by means of imaging two diaphragms on top of one another with a beam deflection system arranged therebetween are carried out in the manner already known from the prior art (e.g., U.S. Pat. No. 6,175,122 B1, U.S. Pat. No. 6,614,035 B2). Also, the generation and projection of special characters  46  (see  FIG. 7   b ) or the imaging of parts thereof which are provided (selected) through one of the larger openings  44  in the first multiple-format diaphragm array  41  and a character  46  in the second multiple-format diaphragm array  42  are known. 
     The stigmator  23  is provided for correcting possible astigmatism in the crossover  111  of the illumination system  2 . 
     The principal innovation of the invention consists in the additional possibility of the beam cross section control of an array (group) of particle beamlets  118  by means of multibeam deflector arrays  51 ,  52  in the vicinity of at least one of the multiple-format diaphragm arrays  41  and  42  so that variably shaped particle beamlets  118  of small beam cross-sectional area (5 to 20 μm) can be generated in an individually controllable manner simultaneously or successively within the same particle beam column without a mechanical changing of diaphragms. 
     The completely independent control of the size of the individual beam cross section in two coordinate directions lateral to the beam direction and the additional individual position deflection of every particle beamlet  118  on the substrate  91  make possible a substantially faster simultaneous exposure of a plurality of different structures of a chip design to be exposed on the substrate  91 . 
     However, since a chip design to be exposed on the substrate  91  usually also contains some large structures or frequently recurring characters  46 , it is often advantageous to be able to select the most productive beam-shaping diaphragm group  45  (see  FIGS. 7   a ,  7   b ) for the exposure of such structure regions without having to exchange one or both multiple-format diaphragm arrays  41  and  42 . This diaphragm selection initially takes place within the illumination system  2  by means of the illumination group selector  22 . 
     When the first multiple-format diaphragm array  41  is illuminated by an illumination group  117  installed in the illumination system  2  in the region of a beam-shaping diaphragm group  45  (see  FIG. 7   a ), an array of particle beams  118  is generated which passes at least one multibeam deflector array  51 , three collective group deflection systems  351 ,  352 , and  353 , and a correction lens  33  in addition to the two condenser lenses  31  and  32  on its path through the condenser system  31 - 32  to the second multiple-format diaphragm array  42 . 
     The at least one multibeam deflector array  51 ,  52  makes possible an individual displacement of every individual particle beamlet  118  generated through the first multiple-format diaphragm array  41  in two coordinate directions as will be explained in more detail in the following with reference to  FIGS. 3   a  and  3   b  and  FIGS. 4   a  and  4   b.    
     A cropping of each particle beamlet  118  depending on its individual lateral displacement is carried out at the location of the second multiple-format diaphragm array  42  as is indicated in  FIG. 7   b  by the heavier hatching of the partial beam cross section  47  in that the individual particle beamlets  118  are reduced to the average area of the partial beam cross section and respective diaphragm aperture of the multiple-format diaphragm array  42 . 
     The use of specially structured multibeam deflector arrays  51 ,  52  and possibly additional multibeam deflector arrays  53  or  54 , whose specific constructions are shown in  FIGS. 3   b ,  4   a ,  4   b  and  5 , make possible an additional individual position control of crossovers  111  and  112  for each particle beamlet  118  within the array of (small-format) particle beamlets  118  regardless of their individual format size. Accordingly, after the particle beam  11  is split into particle beamlets  118 , a usually narrowly limited crossover  111 ,  112  or  114  can be distributed into partial crossovers which no longer coincide spatially. Further, notwithstanding this advantageously intended spatial distribution of individual partial crossovers, the term crossover  111 ,  112  or  113  will continue to be used in the following to associate the position of the individual crossovers of an orthogonal plane to the optical axis  115 . 
     A multi-stage group deflection system  35  in the area of the twofold condenser system  31 - 32  serves to control the particle beamlets  118  when an illumination group  117  in the area of larger diaphragm apertures  44  (30 to 200 μm) of the multiple-format diaphragm array  41  is selected. 
     When a three-stage group deflection system  35  is used, as is designated more exactly in  FIGS. 1 ,  2 ,  8  and  9  by group deflection systems  351  to  353 , the middle deflection system  352  preferably makes it possible to control the beam cross section (format size control) or the selection of special diaphragm structures  46  ( FIG. 7   b ) in the second multiple-format diaphragm array  42 , and deflection systems  351  and  353  are provided for blanking individual particle beamlets  118  so that these particle beamlets  118  either already impinge directly on the second multiple-format diaphragm array  42  or impinge on the aperture diaphragm  7  positioned in the crossover  113  farther along the beam path. 
     Since the multiple-format diaphragm arrays  41  and  42  are subjected to constant bombardment by the particle beam  11  and particle beamlets  118 , it can be advantageous to arrange a plurality of multiple-format diaphragm arrays  41 ,  42  in such a way that they are displaceable lateral to the optical axis when required (e.g., because of wear or other design requirements) as coupled, i.e., etched on a chip, multiple-format diaphragm arrays ( 41 ′,  41 ″, . . . and  42 ′,  42 ″, . . . , respectively) and are therefore exchangeable without having to readjust the particle beam column. A variant of this kind is shown by way of example in  FIG. 9  by exchangeable, identical multiple-format diaphragm arrays  41 ′ and  42 ′. 
     Further, a correction lens  33  can be provided in the beam modulator system  3  between the condenser lenses  31  and  32 . This correction lens  33  makes possible a highly accurate angular orientation of the image of the first multiple-format diaphragm array  41  at the location of the second multiple-format diaphragm array  42  to compensate for mechanical adjustment tolerances. 
     The portion of the illumination control and multi-shape beam control described above is followed farther along the beam path of the particle beam column in direction of the substrate stage  9  by a reduction system  6  which carries out a reduced imaging of the second multiple-format diaphragm array  42  on the substrate  91  located on the substrate stage  9  by means of electromagnetic lenses  61  and  62 . Apart from the two-stage reduction optics  61 - 62  shown in the drawing, optics with only one or with three lenses can also be used. 
     The reduction system  6  is outfitted with diverse deflection systems for controlling the particle beam positions on the substrate  91  such as beam return system  63 , beam tracking  65 , micro beam deflection  66  and macro beam deflection  67  as well as stigmators  64  and  69  and a fast focusing lens  68 . The imaging scale for the reduced imaging of the second multiple-format diaphragm array  42  on the substrate  91  is typically 30:1-100:1. 
     A third multibeam deflector array  53  (as precision positioning system for the position of every particle beamlet  118  on the substrate  91 ) is located at a distance of about 10-20% of the distance between the second multiple-format diaphragm array  42  and the next crossover  112 . This precision positioning system  53  is identical in principle to the multibeam deflector arrays  51  and  52 , but has a different scaling factor. It permits a small individual position displacement of every particle beamlet  118  (5 to 20 μm) lateral to the beam direction. 
     The electronic control of the two respective deflector cell arrays  57  within each of the multibeam deflector arrays  51 ,  52  and  53  is carried out by an individual calibrated coupling matrix which is generated and suitably further processed, according to  FIG. 6 , in order to impress on all of the particle beamlets  118  in the array an individual format size (S xi , S yi ), an individual precision positioning (SM xi , SM yi ) and an individual position of the crossover  112 . For this purpose, the actual parameters derived from the chip design to be exposed, the format size (S xi , S yi ) and (SM xi , SM yi ) and precision positioning, are converted in a digital coupling matrix computing unit  37  with suitable transformation coefficients and blanking signals for individual particle beamlets  118  into individual deflection values for every deflector (electrode pair  573 ) of the total of six deflector cell arrays  57 . Because of the closely adjacent structure of the deflector cell arrays  57 , the individual deflection values from the coupling matrix computing unit  37  are then converted into corrected deflection values in a crosstalk correction computing unit  38  with crosstalk coefficients which take into account the special structure of the deflector cell arrays  58  and are fed to a data multiplexer  39 . The data multiplexer  39  generates a high-speed data stream of deflection values to the individual demultiplexers  59  of the six individual deflector chips  55  (see  FIG. 3 ). The entire procedure for calculating the individual corrected deflection values is carried out in the computing units  37  and  38  in real time for all of the multideflector arrays  51 ,  52  and  53  (pipeline structure). 
     A two-stage beam return system  63  and a two-stage stigmator  64  are arranged in the beam path in front of the first reduction stage (lens  61 ). The beam return system  63  ensures that the particle beamlets  118  are deflected again to the optical axis  115  by the respective beam-shaping diaphragm group  45  being used, which should advisably be located outside the optical axis  115 , without influencing the position of the crossover  112  along the optical axis  115 . This serves to reduce aberrations. Also, the stigmator  64  can help to reduce distortion. 
     The reduced intermediate image  119  of the portions of the partial beam cross sections  47  which pass through the diaphragm apertures  44  and which were defined by the illumination area  117  through the first multiple-format diaphragm array  41  ( FIG. 7   a ) and were changed individually by the group deflection systems  35  and the individual deflection systems of the multibeam deflector arrays  51  and  52  and the change in shape and size by the second multiple-format diaphragm array  42  are imaged once again in reduced manner on the substrate  91  by the second reduction stage (lens  62 ). 
     In so doing, the aperture diaphragm  7  defines the substrate aperture and serves as a blanking diaphragm for temporarily unused particle beamlets  118 . The beam position of the reduced image of the beam-shaping diaphragm group  45  being used can be positioned on the substrate  91  in the conventional manner by microbeam deflection  66  and macrobeam deflection  67 . 
     Further, according to the construction shown in  FIG. 1 , a deflection system  65  for beam tracking during the exposure of the substrate  91  on the continuously moving substrate stage  9  can be advantageous. A fast focusing lens  68  in cooperation with another stigmator  69  serves for continuous, exact focusing of the particle beamlets  118  on the substrate  91  based on the values measured by a height sensor  81 . Typical unevenness of the substrate  91  and a possible deflection defocusing can be corrected in this way. The backscattering particle detector  82  serves to detect marks and for beam calibration. 
     With the construction of the particle beam column according to  FIG. 1  remaining the same in other respects,  FIG. 2  shows another configuration of the multibeam deflector system  5 . In this example, all of the multibeam deflector arrays  51  are positioned in the vicinity of the multiple-format diaphragm array  42 . In so doing, the multibeam deflector array  51  arranged in front of the second multiple-format diaphragm array  42  provides for the beam deflection of the particle beamlets  118  to achieve an individually differing cropping of its cross sections through the multiple-format diaphragm array  42 . The multibeam deflector array  52  causes the inclinations of the individual particle beamlets  118  to be reset by amounts opposite to those by which they were deflected by means of the first multibeam deflector array  51  (for purposes of the format cropping by the second multiple-format diaphragm array  42 ). The precision deflection of the individual particle beamlets  118  for their position on the substrate  91  is carried out by the third multibeam deflector array  53  in the form of a precision positioning array. 
       FIG. 8  shows the pupil beam path of another variant of a particle-optical imaging system for a multiform beam lithography system. As in the variant according to  FIG. 1  or  FIG. 2 , the illumination of the particle beam source  1  is determined through the beam outlet  110  and the outlet aperture diaphragm  116 . 
     In this constructional variant, however, the condenser lens  21  of the illumination system  2  provides for a telecentric illumination of the first multiple-format diaphragm array  41 . The illumination group selector  22  serves for beam alignment and specific selection (i.e., spatially defined illumination) of a determined beam-shaping diaphragm group  45  on the multiple-format diaphragm array  41  ( FIG. 7   a ). The stigmator  23  is provided for correcting astigmatism that may possibly occur in the crossover  111 . 
     As in the first variant, the condenser lens system  31 - 32  provides for a 1:1 imaging of the first multiple-format diaphragm array  41  on the second multiple-format diaphragm array  42 . The multibeam deflector arrays  51  and  52  make it possible to individually displace each of the particle beamlets  118  generated by the second multiple-format diaphragm array  41  within the array in two coordinate directions. A cropping of every particle beamlet  118  according to its individual displacement is carried out at the location of the second multiple-format diaphragm array  42 . As in the first variant, three other deflection systems  351 ,  352 ,  353  in the area of the condenser lens system  31 - 32  serve to control beam-shaping diaphragm groups  45  with large beam cross sections. Also, lens  33  is again used for highly accurate angular orientation of the image of the first multiple-format diaphragm array  41  at the location of the second multiple-format diaphragm array  42 . 
     In contrast to the first constructional variant according to  FIG. 1 , three-stage reduction optics ( 60 ,  61 ,  62 ) are used in  FIG. 8 . The lens  60  generates an intermediate image of the crossover  111  and provides for a continued telecentric beam path with respect to the second multiple-format diaphragm array  42 . The reduction system  6  further comprises lenses  61  and  62 , as was described with reference to the variants according to  FIGS. 1 and 2 , and provides for the corresponding reduced imaging (30:1 to 100:1) of the second multiple-format diaphragm array  42  on the substrate  91 . Both variants according to  FIG. 1  and  FIG. 8  use the same conventional positioning, measuring and correction systems. 
     The main advantage of the variant according to  FIG. 8  over the constructions in  FIGS. 1 and 2  is that the third multibeam deflector array  53  for individual precision positioning of the beamlets  118  on the substrate  91  can be constructed identical to the two multibeam deflector arrays  51  and  52 . This facilitates alignment processes. 
     A principal advantage of the imaging variant shown in  FIG. 8  consists in the prevention of an intermediate image of the beam outlet  10  of the particle source  1  in front of the first multiple-format diaphragm array  41 , which occurs as a crossover  110  in the first variant (according to  FIG. 1 ). 
     Since the total flow of particles is always higher in the illumination system  2  than in the following imaging stages, significant interactions take place in the crossover  110  of the particle beamlets  118 . Such interactions can contribute to a disruptive energy expansion in the beam which causes additional chromatic errors in the subsequent lenses and accordingly ultimately impairs resolution. Therefore, the arrangement of the particle columns described above with reference to  FIG. 8  is more advantageous in this respect than the variants according to  FIGS. 1 and 2 . 
       FIG. 9  shows a modified variant of the particle beam column with telecentric illumination according to  FIG. 8 . Instead of the three multibeam deflector arrays  51  to  53  which were originally provided in the beam modulator system  3 , four such multibeam deflector arrays  51 - 54  are provided. While the first multibeam deflector array  51  organizes the individual position control of the particle beamlets  118  in the crossover  111  to generate the least possible interaction between the individual particle beamlets  118 , the second multibeam deflector array  52  is provided for separate orientation of the individual particle beamlets  118  for cropping their format through the second multiple-format diaphragm array  42 . The third multibeam deflector array  53  causes the individual changes in direction of the particle beamlets  118  in the course of the format cropping to be reset, and the fourth multibeam deflector array  54 , as precision positioning array, again provides for the individual positioning of the particle beamlets  118  on the substrate  91 . 
     In the following, the construction and operation of the multibeam deflector arrays  51  and  52  and precision positioning arrays  53  and  54  will be discussed in more detail. The latter are constructed so as to have substantially the same construction and operation at the multibeam deflector arrays  51  and  52  but are reduced by scaling. 
     The multibeam deflector arrays  51  to  54  each have two deflector cell arrays  57  which are closely (&lt;1 mm) adjacent to one another in the beam direction of the particle beamlets  118  and are oriented laterally substantially orthogonal to one another and substantially comprise a uniform arrangement of electrode pairs  573  and screen electrodes  574 . A 90-degree arrangement of the electrode pairs  573  is shown in  FIG. 4 , and an enlarged section thereof is shown in  FIG. 5 . The deflector chip  55  in  FIG. 4   a  must be imagined as flipped over the deflector chip  55  shown in  FIG. 4   b  along the center of the drawing sheet such that the surfaces of the deflector chips  55  on which the electrodes  573  and  574  are arranged face one another. 
     The control of the multibeam deflector arrays  51 ,  52 ,  53 , whose hardware embodiment is shown in  FIG. 3   a , is carried out by electronic computing units in a pipeline structure as is shown in  FIG. 6 . The coupling matrix, which has already been mentioned, ensures that all of the particle beamlets  118  in the beamlet array can have an individual cross-sectional size (S xi , S yi ), an individual precision positioning (SM xi , SM yi ), and an individual position in the crossover  112 . There are basically two position adjustments of interest for the individual position of the particle beamlets  118  in the crossover  112 :
         a) exactly on the optical axis  115 —for exposure—or   b) as far away as possible from the optical axis  115 —for blanking the particle beamlet  118  at the outlet aperture diaphragm  7 .       

     In order to determine the deflection values for the individual deflector cells  571  of a plurality of multibeam deflector arrays  51 ,  52 ,  53  (and possibly  54 ) from the values for the individual format size (S xi , S yi ) and the individual precision position (SM xi , SM yi ) of every particle beamlet  118  by means of an individual coupling matrix and to then carry out a compensation of the crosstalk caused by deflector cells  571  adjacent in the plane, one or more digital computing units are required for implementing linear transformations consisting of multiplications and additions. Dummy deflector cells  572  which are provided in the design of the deflector cell arrays  57  do away with the necessity of special handling of the particle beamlets  118  lying at the edge and in the corners of the particle beamlet array so that all deflection values can be calculated according to the same algorithm, although this algorithm relies on individual transformation coefficients or coupling coefficients. A high degree of parallelizability in the calculation and control electronics is ensured by the property of the design of the deflector cell arrays  57  whereby an outer row of passive deflector cells (dummy deflector cells  572 ) is arranged around the active deflector cells  571  which each deflect a particle beamlet  118 . 
     Since the coupling coefficients depend on the actual alignment state of the deflector cell array  57  of the particle beamlets  118 , the transformations cannot be processed as part of an offline data processing, but rather must be carried out in real time during the exposure. 
     For reasons of productivity, computing architectures which work in a purely sequential manner (deflection value after deflection value, beamlet after beamlet) cannot be used. Computing blocks which operate in parallel and which, e.g., are associated in each instance with a particle beamlet  118  or a row or column of particle beamlets  118  in a multibeam deflector system comprising three or four multibeam deflector arrays  51  to  54  are required in order to achieve sufficient throughput rates. Further, by reducing the algorithm to sub-operations of addition and multiplication which are carried out in blocks working in parallel, it is possible to combine the calculation functions with those of data transfer so that pipeline structures or systolic processor arrays can be used. Arrays of this kind can be realized in modern programmable logic circuits (FPGAs) having very high scale integration which also provide the necessary bandwidth for input and output. 
     After digital calculation of the individual deflection values for each deflector chip  55 , a digital-to-analog conversion must be carried out to provide the deflection potentials for the individual deflector cells  571 . Since every deflector cell  571  comprises pairs of electrodes  573  and, therefore, requires two control voltages symmetric to a ground potential (screen electrode  574 ), a total of 12n voltage potentials must be generated for controlling n particle beamlets  118  in six deflector planes (i.e., in three double deflector arrays with deflection directions X and Y) of the first and second multibeam deflector arrays  51  and  52  and the third multibeam deflector array  53  operating as precision positioning array. In implementing this circuit component, it is useful to use multichannel active components such as multi-DA converters  58  with corresponding multi-operational amplifiers. 
     As the quantity n of particle beamlets  118  to be controlled increases, the construction and connection technology for supplying the 12n voltages of DAC boards located outside the electron-optical column in the vacuum region of the particle beam column becomes increasingly difficult. Therefore, after n&gt;64, instead of transferring the individual analog voltages separately, a preferred solution is to transfer the digital control values by multiplexing via a few serial high-speed connections with data rates of greater than 1 gigabyte/second into the vacuum region of the particle beam column. In this respect, the transfer can be realized by means of differential electric signals or optically by means of glass fibers or free space optics. The demultiplexing of the control data and D-A conversion thereof can then be carried out directly on each deflector chip  55  of the multibeam deflector system  5 . 
     A control of the kind mentioned above is shown schematically in  FIG. 3 . Two integrated demultiplexer chips  59  supply four integrated multi-DA converters  85  on the right-hand and left-hand side, respectively, to control the deflector chip  55  which is positioned almost in the center. Two independent deflector boards which are outfitted with identical electronics modules and each of which holds a deflector chip  55  and is supplied with separate control signals are used for two deflector cell arrays  57  arranged one on top of the other in order to realize individually the X-deflection and Y-deflection of the separate particle beamlets  118  with pairs of electrodes  574  oriented orthogonally relative to one another in the two planes of the deflector cell arrays  57  situated one above the other. 
     This circuit arrangement solves the problem of the signal feed and also satisfies the requirement for short setting times for the deflector cell arrays  57  through a compact construction and very short, low-capacitance control lines. 
     As is shown in  FIGS. 4   a  and  4   b  and in  FIG. 5  in specific constructions of the deflector chips  55 , deflector chip cutouts  56  are incorporated in the deflector cell array  57 , and these deflector chip cutouts  56  are associated with the beam-shaping diaphragm group  45  for small-format particle beamlets  118  (5-20 μm) of the multiple-format diaphragm array  41  and have identically shaped or larger deflector plate cutouts  56  so that the individual particle beamlets  118  provided by the multiple-format diaphragm array  41  are not cropped but rather are deliberately influenced individually with respect to their beam direction. 
     To this end, an individual deflector cell  571  comprising an electrode pair  573  and two screen electrodes  574  is associated with each individual diaphragm aperture  44  of the beam-shaping diaphragm group  45  of a multiple-format diaphragm array  41  or  42  as is shown schematically in  FIG. 5  and in an enlarged section from  FIG. 4   a.    
     In this connection, each of the screen electrodes  574  which are located between the parallel-oriented electrode pairs  573  of two deflector cells  571  can simultaneously shield the two neighboring deflector cells  571 . In spite of the screen electrodes  574 , the fields of the individual deflector cells  571  on the multibeam deflector arrays  51 ,  52  and the precision positioning array  53  act not only on the particle beamlet  118  passing through its associated individual deflector cell  571  but also on the adjacent particle beamlets  118  (crosstalk). This crosstalk is corrected in the following manner: 
     When an 8×8 beam-shaping diaphragm group  45  is used in an advantageous manner, it has proven favorable, for example, to outfit the deflector chips  55  with 10×10 deflector cells  571 ,  572 . In order to present the construction of optimized deflector cell arrays  57  in a simpler and clearer manner, the multibeam deflector arrays  51  and  52  shown in  FIGS. 4   a  and  4   b  are arranged with a 6×6 deflector cell array  57  with 4×4 active deflector cells  571  within an outer frame of one dummy deflector cell  572 , no deflector plate cutout  56  being provided between the electrode pair  573  of the latter. Accordingly, the 4×4 array of deflector cells  571  is supplemented in such a way that a dummy deflector cell  572  is located on all sides around the field of the sixteen deflector plate cutouts  56 . 
     The following estimates for the crosstalk behavior of the deflector cell array  57  are given for a real 10×10 deflector cell array  57  using this scheme in the same way with an 8×8 array of active deflector cells  571 . 
     Disregarding the crosstalk for the time being, the voltages at the 10×10 deflector cells  571  are:
 
 U   ij   0   i,j= 0 . . . 9.
 
     The outer rows of the deflector cell array  57  are dummy deflectors  572  to which no voltage is applied, i.e.:
 
 U   0j   0   =U   9j   0   =U   i0   0   =U   i9   0 =0 i,j= 0 . . . 9.
 
     The actual deflector voltages for the active deflector cells  571  are:
 
 U   ij   0   i,j= 1 . . . 8.
 
     By inserting dummy deflectors  572 , every active deflector cell  571  “sees” the same surroundings. Therefore, the “active deflector cell array”  57  comprises only the inner 8×8 active deflector cells  571  whose voltages must be corrected owing to crosstalk. Let the corrected voltages be:
 
 U   ij   0   i,j= 0 . . . 9.
 
     Since the outer frames around the active deflector cells  571  are dummy deflectors  572 , then:
 
 U   0j   =U   9j   =U   i0   =U   i9 =0 i,j= 0 . . . 9.
 
     The deflecting action of an individual deflector cell  571  is changed by the crosstalk due to the interfering effect of the other deflector cells  571  of the deflector cell array  57 . Since the crosstalk effect is small, it can be considered as sufficient to allow for the interfering effect of the eight immediate neighbors of a deflector cell  571  in question. The simplest possibility for correcting crosstalk consists in applying a correcting voltage to the deflector cells  571  in question which compensate for the crosstalk effect of the voltages of the eight directly adjoining deflector cells  571 . 
     In this regard, the following exceptions are made:
         1. The crosstalk effect on deflector cells  571  situated farther away (outside of the eight immediate neighbors) is disregarded.   2. The fact that the correcting voltages applied to the deflector cell  571  in question are themselves subject to crosstalk (second-order effect) is disregarded.   3. An inside deflector cell  571  is influenced exclusively by the crosstalk from its eight directly adjacent deflector cells  571 .       

     Every deflector cell  571  within a field of nine adjacent deflector cells  571  and  572  can be considered sufficiently defined by the exceptions mentioned above. 
     The eight neighboring cells of a selected, inside deflector cell  571  are designated by the symbols LO, LM, LU, MO, MU, RO, RM, RU which identify the positions of the eight neighbors according to the following scheme: 
     
       
                 
         
             
             
         
      
     
     Assuming that only the inner deflector cell  571  of the nine deflector cells  571  in question are controlled and causes the deflection “1” for “its” particle beamlet  118 , this gives a deflection of the following magnitude due to the crosstalk on the eight adjacent particle beamlets  118 :
 
 C   LO   ,C   LM   ,C   LU   ,C   MO   ,C   MU   ,C   RO   ,C   RM   ,C   RU .
 
     The quantities C LO , C LM , etc. are the crosstalk coefficients. In case of a deflector cell array  57  comprising uniform, structurally identical deflector cells  571 ,  572 , these quantities are typically less than 5%. In theory, they can be determined by suitable modeling or even empirically. 
     It is further assumed that these coefficients are identical for all of the inner deflector cells  571 . 
     Let an inner deflector cell  571  in the 10×10 deflector cell array  57  considered above have the uncorrected control voltage U ij   0 . The corrected control voltage would then be:
 
 U   ij   =U   ij   0   −C   RU   *U   i−1,j−1   0   −C   MU   *U   i−1,j   0   −C   LU   *U   i−1,j+1   0   −C   RM   *U   i,j−1   0   *−C   LM   *U   i,j+1   0   −C   RO   *U   i+1,j−1   0   −C   MO   *U   i+1,j   0   −C   LO   *U   i+1,j+1   0   i,j= 1 . . . 8
 
     In this respect, it is not taken into account (according to the first exception mentioned above) that the correction of the control voltage of an adjacent deflector cell  571  also acts on the next deflector cell but one  571  or  572  due to the crosstalk (higher-order effects are disregarded). This appears allowable because the coefficients C LO , C LM , etc. are quantitatively less than 0.05. 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Technology Category: h