JP5607145B2 - Charged particle optical system with electrostatic deflector - Google Patents

Description

  The present invention is a charged particle optical system comprising an electrostatic deflector for deflecting at least one beamlet of charged particles, the electrostatic deflector comprising first and second electrodes, The beamlet relates to a charged particle optical system in which the beamlet passes between a first electrode and a second electrode, and the beamlet is deflected when a potential difference is set between the electrodes.

  The invention further relates to a method of using such a charged particle optical system.

  One such charged particle system is known from US 6,897,458. This system is a maskless lithography system. According to this lithography system, a beam of charged particles such as electrons is split into a plurality of beamlets at an aperture plate. The beamlet is then focused to the desired diameter and passed through a beamlet blanker array. The beamlet blanker array includes a blanking electrostatic deflector. When a voltage is applied to the blanking deflector, the beamlet deflects and terminates at a beamlet stop array located behind the beamlet blanker array. If not deflected, the beamlet reaches a set of lenses. The lens focuses the beamlet on the target surface. The scanning deflection means moves the beamlet together in one direction across the target surface.

  Electrostatic deflectors can be used for blanking and scanning deflectors in such maskless lithography systems and other high-speed deflection applications. Typical examples are oscilloscope tubes, electron beam lithography systems, inspection systems and streak cameras. A common type of electrostatic deflector is a planar deflector. The planar deflector comprises two parallel plates with opposite voltages, ie + V and −V. These generate an electric field in the (x-) direction perpendicular to the plate. Such planar deflectors deflect the beam in only one direction. The disadvantage of planar deflectors is that the x and y deflections must be applied sequentially at different distances (i.e. different z positions) to the target, e.g. a semiconductor material wafer.

  Another type of deflector is a multipole deflector. The most common example of a multipole deflector is an octupole deflector comprised of a curved plate with a cylindrical or conical portion. By applying an appropriate combination of electrode potentials to the plate, deflection can be applied simultaneously in two orthogonal directions (x and y). The disadvantage of this deflector type is its complex structure.

  The above-mentioned prior art reference US 6,897,458 identifies a specific planar electrostatic deflector for use as scanning deflection means. The deflector includes an electrode configured to deflect a set of electron beamlets in one direction. The electrodes can have a strip shape and be placed on a suitable plate. Instead, strip-type electrodes are placed on the side of the set of projection lenses facing the target surface or alternatively on a different plate between the set of projection lenses and the target surface. Can be.

  FIG. 10 shows a schematic cross-sectional view of a part of the prior art electrostatic deflector 11. The deflector 11 includes a first strip 131, a second strip 132, and a third strip 133. These are on the substrate 150. A passage window 140, for example a through hole, extends between the strips 131, 132, 133 of the substrate 150. The lithography system is designed so that charged particles, ie electron beamlets, pass through the passage window 140. The first and third strips 131, 133 are part of the first electrode, while the second strip 132 forms part of the second electrode. Accordingly, the second strip 132 has a polarity opposite to that of the first and third strips 131, 133. In this example, the second strip 132 is a negative electrode. When a potential difference is applied between the first and second electrodes, an electric field is generated toward the second strip 132. Considering electrode strips 131, 132, 133 that are arranged side by side, ie, opposite polarity, 131, 132, the electric field generated between the first and second strips 131, 132 is the second and third strips 132. , 133 has the opposite direction to the electric field generated. As a result, the beamlet 7 is deflected in the opposite direction by the electric field.

  Such deflection has been found to have drawbacks. That is, when the beamlet 7 is deflected, the surface area covered by the grid of the beamlet 7 becomes larger than when it is not deflected. Problems arise when writing patterns on a target surface that is significantly larger than this surface area because of this difference in surface area. Therefore, it is necessary to match the pattern of adjacent surface areas without having an undesirable overlap or gap between adjacent surface areas.

  Another type of electrostatic deflector can be seen from EP 1993118. This type is a blanker deflector that uses an array of electrodes protruding from the substrate. This array can be deflected simultaneously in two directions and is designed to allow individual addressing of individual electrodes in the array. The latter feature resulted from the need to deflect each beamlet separately in a blanker deflector. There are holes between the electrodes on the substrate, one active and one grounded or opposite polarity, through which any beamlet can pass. The electrodes are wall-type and can be formed on two stacked substrates in such a way that the electrodes are at least partially facing each other. The height of these electrodes is on the order of 35-50 μm, and the distance between them can be less than 10 μm. When the electrodes are on the same substrate, the height can be less than 10 μm and the mutual distance can be as much as 0.5-2 times the height. The substrate can be made thinner than a thin film with protruding electrodes.

  However, this type of deflector has the disadvantage that it does not provide sufficient uniformity when it is intended to be applied as a scanning deflector. If one of the electrodes is present on the second substrate, it creates a stray electric field, resulting in a nearly uncontrollable result. This is not a problem when used as a blanker deflector. When a potential difference is applied between the electrodes in the blanker deflector, the beamlet deflects and terminates at the beam stop. As long as the beamlet terminates somewhere at the beam stop, it does not matter whether the deflection is slightly larger or smaller. However, when applied as a scanning deflector, such changes directly reduce the resolution of the pattern provided. Furthermore, stray electric fields can lead to reduced beamlet uniformity. This can lead to poor resist results and / or incorrect beam positioning, as well as improper (ie, failed) pattern generation.

  In short, the prior art has drawbacks and is overcome by the present invention.

  In a first aspect of the invention, there is provided a charged particle optical system comprising an electrostatic deflector that deflects at least one beamlet of charged particles. The deflector includes first and second electrodes, the beamlet passes between the first and second electrodes, and each of the first and second electrodes is at least one strip. And the strip is at least partially freestanding.

  Since the electrode of the deflector in the charged particle optical system of the present invention comprises an at least partially self-supporting strip, the deflector can provide an electric field with a uniform field strength. Have This better uniformity is based on contributions from several results. First, the use of free standing strips suggests no continuity. Continuity tends to adversely affect uniformity. For example, an insulating support can affect the system as a parasitic capacitor. Furthermore, free standing electrodes can be made in a single etching step. This makes it possible to reduce the distance between the electrodes and further reduce the potential voltage difference with respect to the electrodes. Such a reduction leads to an improvement in the uniformity of the deflector, especially when applied in combination with a high scanning frequency. The high scanning frequency is, for example, a frequency exceeding 100 kHz, preferably in the range of 300 to 3000 kHz, and more preferably 500 to 1500 kHz.

  Furthermore, a strip having a relatively large surface area on the side of the strip perpendicular to the direction of the electric field can be provided. Providing such a large surface area further improves the mechanical stability of the free standing strip. As a result, the contribution of the electric field spun up between the two opposing strips is large compared to the contribution of the stray component of the electric field. This is beneficial because stray components are difficult to predict and control and therefore tend to shift the trajectory of the intended beamlet. Furthermore, overall, the deflection is better controlled.

  Instead of individually addressing a single beamlet, it is appropriate that the field be uniform across the grid of beamlets. These features make this deflector particularly convenient for performing scanning deflections, but other uses are not excluded. In particular, since the output is highly accurate and uniform, it can be used to perform other deflection and / or filtering.

  In a suitable embodiment, the strips are placed at a distance close to each other compared to the surface area facing the opposite strip. For example, each electrode comprises at least one strip. The strips extend substantially parallel and define a passage window through which a plurality of beamlets pass. The passing window has a width in a direction perpendicular to the strip. Setting a potential difference between the electrodes generates an electric field in a direction perpendicular to the strip. The strip has a height, a width and a transverse direction in three mutually orthogonal directions. The height of the strip is greater than the width of the passage window. This results in a large straight field and good field uniformity compared to the stray electric field.

  Furthermore, if the distance is relatively short, the drive voltage can be made relatively small while continuing to meet the deflection angle requirements. A design with a small drive voltage, eg, less than 10V, is effective for two or more reasons. First, the drive electronics that supplies the voltage at a switching frequency of 1 MHz or higher can be kept relatively simple. That is, a dedicated high voltage power transistor is not required. A dedicated high voltage power transistor can consume a large amount of power and / or constitute a generally limited and limited life component. Furthermore, the use of small voltages greatly reduces the risk of uncontrolled discharge between the electrodes that actually cause damage. This is good for reliability and robustness.

  In another embodiment, there are multiple pass windows, and the electric field orientation in each pass window is the same. Scanning in one orientation has been found to simplify the provision of patterning data to the beamlet. This overall improves the accuracy of the scanning process and improves stitching of lines and / or pixels scanned by different beamlets. Here, the term “orientation” is used in contrast to the term “direction”. That is, there are three Cartesian directions x, y, z, and two orientations are combined in one direction. The term “same orientation” is not intended to mean that the electric field in one pass window has a constant orientation in time. In practice, the electric field orientation is preferably reversed within one scanning period. However, the term contemplates that at any moment, the electric fields in the different pass windows have the same orientation. Furthermore, at any moment, the electric fields in the different passing windows preferably have the same magnitude.

  Suitably, an insulating region, preferably an insulating window, is between the first and second passage windows. This is a robust implementation that creates a passing window with equal direction electric fields. Surprisingly, it has been found that the addition of such insulating windows can still meet the specified pitch conditions between the beamlets. This appears to be an advantageous effect using a free standing electrode strip. It is preferred to place the free-standing electrode strips at a short distance from each other. Here, the term “short distance” is used to represent a short distance compared to the distance of the electrodes in the prior art macroscopic deflector and other dimensions in the deflector. doing. Other dimensions within the deflector are, for example, the height of the strip and / or the distance between adjacent passing windows.

  Suitably at least one termination resistor is present. Such a termination resistor accelerates the positioning of the beamlet between the first scanning period and the second scanning period. Here, the term “positioning” refers in particular to positioning the beamlet in the starting position in order to scan the next line during the second scanning period. Furthermore, the beamlets are deflected with the same orientation both in the first scanning period and preferably in all scanning periods. Beamlet positioning is achieved without writing at the same time by setting the voltage on the electrode to a starting value corresponding to the starting position and then switching the beamlet off by operation of the beamlet blanker at the top of the column. Is done. It has been found that deflecting the beamlet in the same orientation in later scanning periods simplifies the supply of patterning data to the beamlet. It is most appropriate to deflect all beamlets with the same orientation.

  In the first implementation, the termination resistor is electrically connected in parallel to the electrode system. In the second implementation, the first termination resistor is electrically connected between the first electrode and ground, and the second termination resistor is electrically connected between the second electrode and ground. Connecting. If a termination resistor is provided in one embodiment, the parasitic capacitance in the deflector is weakened. Parasitic capacitance tends to slow down potential difference switchback. Use of a combination of the first and second implementations is not excluded. It is appropriate to integrate the terminating resistor into the deflector. For example, polysilicon, TaN, TiWN, CrSi resistors are included as commonly applied in passive and active integrated circuits.

  In another embodiment, there is an edge zone that at least partially overlaps an aperture in the substrate. The edge zone comprises a strip of electrodes and defines an electric field with the same orientation as the electric field described above, but without a passage window for the beamlet. Suitably, the edge zone is embodied as an extension of an interdigitated pair of electrodes. However, the edge zone is designed so that there are no beamlets. Adding such an edge zone has been found to be very beneficial for electric field uniformity. Most beneficial is a design in which the first and second electrodes are of opposite polarities and an additional ground electrode is adjacent to the electrode system.

  In another embodiment, the free standing electrode is covered with a coating so as to provide an electrically substantially uniform surface. Such a coating prevents more or less local changes in the surface structure from becoming active in order to create an electric field between the electrodes. Furthermore, such a coating contributes to the uniformity of the electric field. Further, such uniformity helps to reduce the risk of electrostatic discharge.

  In another embodiment, there is a second electrostatic deflector that deflects in a different direction than the first deflector. The different direction may be a direction opposite or orthogonal to the scanning direction, or any other direction different from the scanning direction. The different directions are in particular the directions in the optical surface (for example the surface in which the optical axis appears as a vertical line). A correction orthogonal to the scan direction is beneficial considering the continuous and continuous movement of the lithography system relative to the target surface. This movement is also called mechanical scanning. Suitably this movement is in the same direction as that of another deflector. Such correction is suitably performed at a frequency lower than the scanning frequency. It is appropriate to deflect in the direction opposite to the scanning direction using the same type of deflector used for scanning. In practice, such deflection is part of the scan. Thereby, even when the beamlet is deflected, the beamlet can be passed through the central portion of the optical axis on the effective lens surface of the projection lens configuration. In this manner, spherical aberration caused by deflection through the projection lens configuration is reduced.

  In a second aspect of the invention, a charged particle optical system is provided that includes a scanning electrostatic deflector that deflects at least one beamlet of charged particles. The deflector includes first and second electrodes, and the beamlet passes through a passage window between the first and second electrodes, and when there is an electric field between the electrodes, Originally, the beamlet is deflected. There are a plurality of passing windows, and the electric field orientation in each passing window is the same.

  Scanning in one orientation has been found to simplify the provision of patterning data to the beamlet. Overall, this increases the accuracy of the scanning process and improves the stitching of lines and / or pixels scanned by different beamlets.

  More specifically, the deflector is designed to have a substantially uniform electric field in the active area of the deflector. Surprisingly, it has been found that deflectors with a uniform electric field can be obtained even if the electrodes are placed in this active area. Any potential field disturbers, such as interconnects and capacitors, are defined outside the active area. In addition, edge zones can be specified to be adjacent to the active area in order to flatten non-uniformities due to edge effects. In one embodiment, the field is constrained outside the active area. For example, the field is suppressed by providing an insulating material. In the preferred embodiment, the field is generated only within the active area.

  One preferred embodiment, which acts only in the active area, uses a pair of interdigitated strip electrodes. Another way to achieve this effect is to define the active area by eliminating the underlying carrier. The absence of such an underlying support directly suggests that the field is not disturbed in that area by unavoidable interactions with the underlying support. It is most appropriate to apply a combination of both approaches. The correct way is to provide a strip of free-standing electrodes.

  In a third aspect of the invention, a method of using a charged particle optical system is provided. Suitably, a deflector is used to deflect at least one beamlet of charged particles. A deflector is preferably used for deflecting the plurality of beamlets. Most suitably, voltages of opposite polarities are applied to the first and second electrodes of the deflector. It has been found that driving the deflector with a voltage approximately opposite the ground value (0 volts or another value) gives the best results. Here it will be seen that for proper scanning, the voltage at the electrodes varies according to a predetermined voltage profile. In particular, it has been found that a sawtooth profile is very advantageous when combined with a structure where the electric field has the same orientation anywhere in the deflector. According to the invention, the opposite voltages at the electrodes are of equal magnitude and are preferably less than 10V. Here, 10V is the maximum applied voltage difference from the ground in the case of positive polarity. For negative polarity this is -10V. A smaller voltage, for example, a maximum voltage of 7, 5, or 4 volts is more appropriate. Such smaller voltages are possible with the deflector of the present invention. In the deflector of the present invention, the self-supporting electrodes have a short distance from each other to provide a deflection intensity similar to that of prior art deflectors. The scanning frequency is relatively high and is suitably in the RF range, more preferably an intermediate RF between 300 and 3000 kHz, for example 0.5-1.2 MHz.

  It is appropriate to position the modulated beamlet at the starting position during the positioning period without exposing the target surface and to deflect it from the starting position during the writing period. In particular, this alternate positioning and scanning is performed as a sawtooth profile. This has been found to improve scanning uniformity.

  The scanning frequency is in the radio frequency (RF) range, and it is most appropriate to deflect each beamlet and the other beamlet in the same orientation both within one scanning period and during the following scanning period. . The positioning period is shorter than the writing period. Here, the pattern can be accurately scanned at a sufficient speed. This includes, for example, scanning at a high frequency in one direction in combination with shortening the positioning time by suppressing parasitic capacitance.

  This use is particularly utilized in a method of projecting a predetermined pattern onto a target surface by a maskless lithography system. In addition, this is applied to scan the pattern on the target surface. The method includes the steps of generating a plurality of beamlets, modulating a beamlet size using modulation means supplied with data of a predetermined pattern retrieved from a data storage device, and focusing means. Using to focus the modulated beamlet onto the target surface and to scan the pattern on the target surface by deflecting the modulated beamlet with static electricity.

  In another aspect of the invention, the electrostatic deflector comprises first and second electrodes that are at least partially self-supporting, the electrostatic deflector being between the first and second electrodes. The plurality of beamlets are deflected by the action of an electric field in the plurality of beamlets, the plurality of beamlets pass between the first and second electrodes, and the plurality of beamlets define a passing window, and the passing window The size of the passage window in a direction intersecting the first direction in which the first and second beams extend is equal to the diameter of the beamlet, the plurality of beamlets are arranged in one row, Extending in a first direction, a substantial portion of the electrostatic deflector extends beyond the passing window in the first direction. The substantial part preferably extends in the first direction to several times the beam pitch at the passage window. A deflector deflects the beamlet across a portion in the surface of the target, such as a field on a wafer, in a direction that intersects the first direction. The deflector is a scanning deflector that performs the final writing projection of the system.

  For the sake of clarity, of any of the embodiments outlined above and specified in any of the dependent claims, as well as in the aspects of the invention specified in the independent claims It can be seen that any of these may be combined.

  These and other aspects of the invention will become more apparent with reference to the drawings.

1 shows a simplified schematic diagram of an embodiment of a charged particle multi-beamlet lithography system. Figure 2 shows a top view of a preferred embodiment of the present invention. The details of FIG. 2 are shown in an enlarged view. FIG. 3 shows a schematic cross-sectional view of the embodiment of FIG. FIG. 5 shows a schematic cross-sectional view of the embodiment of FIG. 2 in a direction orthogonal to the schematic cross-sectional view of FIG. FIG. 4 shows a top view of a second embodiment according to the present invention. In accordance with the present invention, a third embodiment is shown. FIG. 2 shows a simplified diagram of a deflector system with a deflector according to the present invention. Figure 2 shows a simplified schematic cross-sectional view of a portion of an electrostatic deflector of the present invention. 1 shows a schematic cross-sectional view of a portion of a prior art electrostatic deflector.

  In the figures, identical reference numbers relate to identical or at least similar technical features. The figures are not drawn to scale and are merely intended to illustrate. The figures show examples and are not intended to limit the claims in any way.

  FIG. 1 shows a simplified schematic diagram of an embodiment of a charged particle multi-beamlet lithography system based on an electron beam optical system, without the normal intersection of all electron beamlets. Such lithography systems are described, for example, in US Pat. Nos. 6,897,458, 6,958,804, 7,084,414, and 7,129,502. . These are incorporated herein by reference in their entirety and assigned to the owner of the present invention. Such a lithography system includes a beamlet generator that generates a plurality of beamlets, a beamlet modulator that patterns the beamlets into modulated beamlets, and a beamlet that projects the beamlets onto a target surface. And a projector appropriately. In general, a beamlet generator comprises a source and at least one aperture array. In general, the beamlet modulator is a beamlet blanker having a blanking deflector array and a beam stop array. In general, a beamlet projector includes a scanning deflector and a projection lens system.

  The lithography system suitably includes a redundant scanning function. Such functionality is known from WO-A 2007/013802 assigned to the assignee of the present application and is incorporated herein by reference. This function compensates for defective or invalid beamlets. This can greatly improve the reliability of the lithography system. In addition to the above elements, a lithography system for redundant scanning may include a sensor and a control unit connected to the sensor to identify invalid beamlets having characteristics that deviate from a predetermined standard. . Connect this control unit to control the system, turn specific beamlets on or off, activate the system against the target, or vice versa, to replace invalid beamlets with valid beamlets . It is preferable to prevent the projection of invalid beamlets. Therefore, the pattern element which is not written remains. Thereafter, unwritten pattern elements are transferred onto the target surface by scanning an effective, displaced beamlet across the surface.

  As will become apparent from the following description, the lithography system 1 of the present invention is very well suited for performing redundant scan functions. Due to the improved accuracy of the scan line toward the target surface, a second scan can be performed that accurately fills the gap left open in the first scan sequence.

  In the embodiment shown in FIG. 1, the lithography system comprises an electron source 3. The electron source 3 generates a uniform diffusing electron beam 4. The beam energy is preferably kept relatively low in the range of about 1 to 10 keV. To achieve this, the acceleration voltage is preferably low and the electron source is preferably maintained at about -1 to -10 kV at ground potential with respect to the target, although other settings may be used.

  The electron beam 4 from the electron source 3 passes through two double octopoles and then through a collimator lens 5 that collimates the electron beam 4. It will be appreciated that the collimator lens 5 can be any type of collimating optics. Next, the electron beam 4 hits the beam splitter. In one suitable embodiment, the beam splitter is an aperture array 6. The aperture array 6 blocks part of the beam and allows a plurality of beamlets 7 to pass through the aperture array 6. The aperture array preferably comprises a plate having a through hole. Accordingly, a plurality of parallel electron beamlets 7 are generated. The system generates a large number of beamlets 7, preferably about 10,000 to 1,000,000 beamlets, but of course the system may use some beamlets 7. Furthermore, it should be noted that other known methods may be used to generate parallel beamlets.

  The plurality of electron beamlets 7 pass through the condenser lens array. The condenser lens array is not shown. The condenser lens array focuses each of the electron beamlets 7 on the surface of the beamlet blanker array 9. The beamlet blanker array 9 preferably includes a plurality of blankers. Each blanker can deflect one or more of the electron beamlets 7. The beamlet blanker array 9 and the beam stop array 10 constitute modulation means 8. Based on the input from the control unit 60, the modulation means 8 applies a pattern to the electron beamlet 7. The components present in the end module position the pattern on the target surface 13.

  In this embodiment, the beam stop array 10 comprises an array of apertures through which beamlets can be passed. In its basic form, the beam stop array comprises a substrate with a through hole. The through holes are usually circular holes, but other shapes can be used. In one embodiment, the substrate of the beam stop array 10 is formed from a silicon wafer with an array of through holes having a regular spacing and can be coated with a metal surface layer to prevent surface charging. In one embodiment, the metal is of a type that does not form a natural oxide film such as CrMo.

  In one embodiment, the path of the beam stop array 10 is aligned with the elements of the beamlet blanker array 9. The beamlet blanker array 9 and the beamlet stop array 10 cooperate to block or pass the beamlet 7. If the beamlet blanker array 9 deflects the beamlet, the beamlet 7 does not pass through the corresponding aperture in the beamlet stop array 10 and is instead blocked by the substrate of the beamlet blocking array 10. However, if the beamlet blanker array 9 does not deflect the beamlet, the beamlet 7 passes through the corresponding aperture in the beamlet stop array 10 and is then projected as a spot onto the target surface 13 of the target 24. The

  The lithography system further comprises a control unit 60. The control unit 60 includes a data storage device 61, a reading unit 62, and a data converter 63. The control unit 60 can be located away from the rest of the system, for example outside the interior of the dust-free chamber. The optical fiber 64 is used to send the pattern data held by the modulated light beam to the projector 65. The projector 65 projects from the end of the fiber (schematically shown in the plate 15) into the electro-optic unit 18, here onto the modulation array 9. The modulated light beam 14 from the end of each optical fiber is projected onto the light sensitive element of the modulator on the beamlet blanker array 9. Each ray 14 holds a portion of pattern data that controls one or more modulators. The transmission means 17 can be used to properly align the plate 15 at the end of the fiber and the projector 65.

  The electron beamlet 7 then enters the end module. In the following, the term “beamlet” refers to a modulated beamlet. Such a modulated beamlet effectively includes a temporally continuous portion. Some of these consecutive portions may have lower strength, preferably zero strength. That is, the portion is a portion that can be stopped by a beam stop. Some parts have zero intensity so that the beamlet can be positioned in the starting position for the next scanning period.

  The end module is preferably configured as an insertable and replaceable unit. The end module comprises various components. In this embodiment, the end module comprises a beam stop array 10, a scanning deflector array 11, and a projection lens arrangement 12, but the end module need not include all of these, These arrangements may be different. The end modules are preferably reduced as much as possible, particularly in the range of about 100 to 500 times, for example 300 to 500 times. As described below, the end module preferably deflects the beamlet. After exiting the end module, the beamlet 7 strikes the target surface 13 located at the target surface. For lithographic applications, the target typically comprises a wafer with a charged particle sensing layer or resist layer.

  After passing through the beamlet stop array 10, the modulated beamlet 7 therefore passes through the scanning deflector array 11. The scanning deflector array 11 deflects each beamlet 7 in the X and / or Y direction, that is, in a direction substantially perpendicular to the direction of the undeflected beamlet 7. In the present invention, as will be described later, the deflector array 11 is a scanning electrostatic deflector capable of applying a relatively small drive voltage. The beamlet 7 then passes through the projection lens arrangement 12 and is projected onto the target surface 13 of the target, usually the wafer at the target surface. Projection lens arrangement 12 preferably focuses the beamlet to a geometric spot size of about 10 to 30 nanometers in diameter. The projection lens arrangement 12 in such a design is preferably reduced by about 100 to 500 times. In this preferred embodiment, it is advantageous to place the projection lens arrangement 12 near the target surface 13. In other embodiments, protective means may be placed between the target surface 13 and the focusing projection lens arrangement 12. The protective means may be a foil or a plate clearly provided with the required aperture. The protective means absorbs the released resist particles before the released resist particles reach any of the sensing elements in the lithography system. Alternatively or additionally, a scanning deflection array 11 may be provided between the projection lens arrangement 12 and the target surface 13.

  Roughly speaking, the projection lens arrangement 12 focuses the beamlet 7 onto the target surface 13. Furthermore, the projection lens arrangement 12 ensures that the spot size of one pixel is accurate. The scanning deflector 11 deflects the beamlet 7 over the target surface 13. Furthermore, the position of the pixels on the target surface 13 must be guaranteed to be accurate on a microscale. In particular, the scanning deflector 11 must operate to ensure that the pixels are aligned with the pixel grid that ultimately constitutes the pattern on the target surface 13. It will be appreciated that the wafer positioning means under the target 13 can properly position the pixels on the target surface on a macro scale.

  Such a high quality projection is appropriate to obtain a lithography system that provides reproducible results. In general, the target surface 13 includes a resist film on a substrate. By applying charged particles, ie electron beamlets, a portion of the resist film is chemically altered. As a result, the irradiated portion of the film dissolves somewhat in the developer, creating a resist pattern on the wafer. Next, the resist pattern on the wafer can be transferred to the lower layer by mounting, etching, and / or deposition processes known in the semiconductor manufacturing art. Obviously, if the irradiation is not uniform, the resist is not uniformly developed and can lead to pattern failure. In addition, many such lithography systems use multiple beamlets. The difference in illumination should not be caused by the deflection step.

  The present invention addresses the objective of projecting multiple scanning beamlets onto the target surface 13 precisely and uniformly. Here, it can be seen that at least the free-standing electrode in the scanning deflector 11 generates a very uniform electric field and further deflects it uniformly to achieve its purpose. Furthermore, it has been found that self-supporting electrodes can be produced that have adequate mechanical strength and that do not create new technical problems that are even more difficult to solve. In one suitable embodiment, the free standing electrode has one or more mechanical resonance frequencies. This mechanical resonance frequency is much lower and / or higher than the selected operating frequency of the scanning deflector. In other words, in this embodiment, applying a voltage difference to the electrodes does not lead to vibration of the free-standing electrode. Such vibrations terminate the uniform field between the electrodes. In particular, in one embodiment, the free-standing electrode comprises a surface structure that provides only small fluctuations and / or disturbances in the electric field.

  FIG. 2 shows a top view of a preferred embodiment of the electrostatic scanning deflector 11 of the present invention. FIG. 3 shows an enlarged view of a portion of FIG. FIG. 4 discloses a schematic cross-sectional view in the first direction. FIG. 5 shows a schematic cross-sectional view in a direction orthogonal to the schematic cross-sectional view of FIG. FIG. 9 shows a simplified diagram.

  FIG. 2 shows several successive strips 31-38. The continuous strips 31-38 are each part of the first electrode 21 of the comb structure or the second electrode 22 of the comb structure. In this embodiment, strips 31-38 together constitute an alternating pair of electrodes. Hereinafter, this is also referred to as an electrode system. Here, the substrate 50 supports the electrode system. However, it is appropriate that the electrode system at least partially overlap the aperture 51 in the substrate 50, with the majority overlapping. For ease of understanding, it can be seen that FIG. 4 shows only continuous strips 31-35. However, even with such a reduction in strips, FIG. 4 fully illustrates the principle. Suitably, the continuous strip from the bridge extends from the first side 101 of the aperture 51 to the second side 102. However, as shown in connection with FIG. 7, this is not considered essential.

  It can be seen that a field is effectively generated in the active area 20, as shown by the dotted line in FIG. 2 for ease of understanding. The self-supporting electrode of this embodiment generates a field mainly by side surfaces. There is no such side surface outside the active area 20. However, the active area 20 can be defined instead. The term “at least partly self-supporting electrode” is intended to describe that a suitable conductor present in the active area is self-supporting or partly self-supporting. The term “self-supporting” is intended to describe that these conductors are not supported by any thin film or other support in the active area. The term “partially self-supporting” means that in a confined area supported by a thin film, mechanical struts, or any other support structure, these conductors are localized and / or totally The purpose is to explain the situation that exists. In a preferred embodiment, the condition of the term “at least partly self-supporting electrode” is met when successive strips are self-supporting in the active area.

  Windows 40, 41 extend between the strips. Some of these are passing windows 40. The other is an insulating region 41. In this preferred example, the insulating region 41 is a window, for example a free space that is not filled with any dielectric or other material. The passing window 40 has a width b. The passing window 40 is a window designed to allow the beamlet 7 to pass through. The passage window can be a hole designed for several beamlets 7 or a groove extending entirely between strips of electrodes. If the passage window 40 is limited to a few beamlets 7, it can be sufficiently limited by providing a support structure (such as a post or beam extending perpendicular to the strip). However, there may be other reasons for limiting the passage window 40. In order to obtain maximum uniformity, it is advantageous to have a relatively long passage window. If the passage window is blocked or restricted, the electric field is likely to change.

  It is preferable that the number of continuous strips is relatively large and the distance between the continuous strips is short. The strips 31-38 have a lateral dimension, i.e. a width a and a height z. The insulating window 41 has a width c. The width b of the passing window 40 is suitably smaller than the total distance 2a + c between the passing windows 40. It is more appropriate to select the width b of the passing window 40 so that at most three rows of electron beamlets 7 pass through the passing window 40. The number of columns is more preferably 2, and the number of columns is most preferably 1. It has been found that reducing the number of rows is more beneficial for producing a uniform field. Most of the lines of force run in a direction perpendicular to the lateral extension of the strips 31-38. For example, this is a significant improvement over prior art macroscopic deflectors that have two, eg, U-shaped electrodes on opposite sides of the aperture. The field strength of such a deflector is not uniform. In particular, near the corners of the electrodes, the field strength is higher, and the sides also cause an electric field disturbance. In the scanning deflector 11 according to the invention, the field strength is very uniform and is clearly more uniform than in the prior art. The scanning deflector shows a change in deflection intensity of less than 5%, more preferably less than 3%, most preferably less than 2%. In one embodiment of the invention, a deflection intensity change of 1 to 1.5% was achieved.

  As a result of such a short width b of the passage window 40, the potential differences 21, 22 with respect to the electrodes are considerably reduced, while still a sufficient deflection angle can be obtained.

  Reducing the potential difference with respect to the electrode provides many benefits. First, the deflector can be electrically driven in a better manner. That is, providing a variable voltage difference across the electrodes can increase speed and / or higher bandwidth. Here, the term “bandwidth” is used as a measure for the uniformity with which the electrical signal is applied. Problems can arise if the bandwidth is too low. The problem is, for example, an uncontrollable delay and change in timing for giving the voltage difference, and a change in the magnitude of the voltage difference. Second, the risk of damaging the deflector as a result of electrostatic discharge is reduced.

  In order to optimize the rigidity, the height z of the strip 31 is designed to be relatively large. The height z is suitably larger than the width b of the passage window 40. Furthermore, increasing the height serves to increase the so-called deflection intensity or alternatively to reduce the potential difference required for a given deflection angle.

  FIG. 9 is a simplified cross-sectional view of a portion of the electrostatic deflector of the present invention. Compared to prior art FIG. 10, the major improvements obtained with the present invention will become apparent. First, the field in the deflector extends straight from the first electrode to the second electrode. In the prior art, the electric field extends over the electrodes. Thus, the uniformity is greater and the field strength is better controlled. Second, in the present invention, the height z of the electrodes 31-36 is greater than in the prior art. In the present invention, since the beamlet 7 is deflected over the entire height z, the deflection appears more slowly. Accordingly, the strength of the field required for the predetermined deflection angle can be reduced. As shown in the figure, the height z is preferably larger than the width b of the passage window 40. Thirdly, the deflector of the present invention includes an insulating window 41 in addition to the passing window 40. Accordingly, all beamlets 7 are deflected in the same direction. In the prior art shown in FIG. 10, the beamlet 7 is deflected in the opposite direction. Therefore, compared to the prior art of FIG. 10, even if the present invention has additional strips, the pitch between the first beamlet and the second beamlet is not increased. If desired, the pitch can even be reduced. Such a small pitch is one step towards patterning of smaller critical dimensions in the lithography system of the present invention. Although not shown in this figure or FIG. 10, prior art deflectors have specific holes through which individual beamlets pass. In the present invention, a plurality of beamlets pass between the first strip and the second strip. In the deflector configuration of the present invention, such as a series of free standing strips, no additional holes are required. Furthermore, the passage of multiple beamlets between the first strip and the second strip instead of through individual holes contributes to uniformity.

  One advantage of this deflector is the position of the ground electrode. The ground electrode 25 is not disposed adjacent to the positively or negatively charged electrode, and exists in an area on the substrate that does not overlap or substantially does not overlap the aperture. In addition, the distance between such a charged electrode and the ground electrode was significantly increased. This helps meet the boundary condition that no electrostatic discharge occurs with damage to the deflector. As a result, since there is no ground electrode in the local area, a continuous strip of the first and second electrodes 21 and 22 can be arranged at a shorter distance. For clarity, it has been determined that the potential of the ground electrode need not be equal to the ground potential (0V) in a normal environment. For example, the ground electrode can be any of fi -10 kV to +10 kV. Therefore, the potential applied to the first and second electrodes 21, 22 is approximately this ground, ie f. i. −10 kV − / + 10 kV. The potential difference between the first and second electrodes 21, 22 is suitably at most 50V, more suitably at most 20V, and even more suitably at 10V at most. . In various embodiments of the present invention, for example, a potential difference of less than 10V was achieved versus 8V, 6V, 5V. Such a lower voltage is appropriate because such a lower voltage allows a driver circuit that is robust and nevertheless fast but still has a high bandwidth. Suitably the bandwidth is at least 5 times the scanning frequency. A bandwidth of 10 times the scanning frequency gives very good results in terms of uniformity. The scanning frequency is suitably at least 100 kHz, more preferably at least 500 kHz or even 1 MHz or higher.

  As shown in FIG. 2, the structure includes a bond pad 28. These bond pads 28 are connected to each of the electrodes through interconnects 29. An interconnect 29 exists between the ground plane areas 25. This is particularly appropriate for higher switching frequencies of approximately 500 kHz and above. Thus, RF effects begin to relate. By implementing the interconnect as a waveguide, such RF properties are significantly suppressed. Those skilled in the art will recognize that other transmission line implementations such as strip lines, transmission lines, etc. may be chosen instead.

  In one embodiment, the electric field orientation in each passing window 40 is the same, as shown in FIG. Since the electric field orientation is equal, all beamlets 7 are deflected in the same orientation. As a result, the shape of the projection grid and the surface area of the beamlet 7 are the same regardless of whether they are deflected or not. This principle is embodied as follows in the illustrated embodiment. That is, the first electrode comprises first and third strips, while the second electrode comprises second and fourth strips. A first passage window exists between the first and second strips. The second passage window is disposed between the third and fourth strips. However, an insulating region exists between the second and third strips. That is, there is no passing window in the insulating region. For manufacturing reasons, the insulating region is suitably a window. In addition, this design can reduce the drive voltage, thus significantly reducing the risk of discharge.

  In this further improvement, a termination resistor is connected in parallel with the electrode system of the first and second electrodes 21, 22. Such termination resistors may be integrated on the deflector substrate. Alternatively, the termination resistor may be a different component, such as a separately assembled resistor that can be mounted on one or more surfaces. A termination resistor is provided to remove any effect on parasitic capacitor positioning time in the system. In particular, the resistance reduces the capacitance and / or the resistance and the parasitic capacitance act together as a filter. As a result, the positioning period is shorter than the writing period. These together define the time required to scan a single line and also the scanning frequency.

  It is most appropriate to mechanically connect a resistor to the heat removal path. The path for removing heat may include a heat spreader, a heat sink, and the like. Most suitably, there is a heat conduction path from the deflector in the vacuum vessel to a location outside the vacuum. When such a resistor is used, since the driving voltage is relatively low, the potential difference with respect to the electrode can be made relatively small. This suggests that heat dissipation for resistance is limited. The benefit of resistance is that the potential difference with respect to the electrode can be reduced more quickly. In practice, the parasitic capacitance of the electrode system is weakened by resistors and further does not prevent this reduction of the potential difference. Said reduction of the potential difference directly corresponds to shortening the time to move the beamlet to the starting position for later deflection. In addition, this increases the scanning frequency.

  4 and 5 show schematic cross-sectional views of the embodiment of FIG. FIG. 4 shows the aperture 51 on the substrate and the mutual position of the strips 31-38 more clearly. FIG. 5 shows that in this embodiment, the strip 31 extends from the first side 101 of the aperture 51 to the second side 102 on the opposite side. In this configuration, the electrode effectively constitutes a bridge that covers the underlying aperture. This is a preferable configuration from the viewpoint of mechanical stability. There is no thin film support on the aperture 51 that serves as a support for the strip, but the strip is at least partially self-supporting. In order to be self-supporting, the strip has dimensions and rigidity to prevent the strips 31-38 from flexing and bending uncontrollably.

  It is appropriate to manufacture this structure based on a semiconductor substrate that can be selectively etched or patterned from both the upper and lower sides. Silicon-on-insulator (SOI) substrates have proven very advantageous for this purpose. That is, the oxide 52 embedded in the substrate serves as an etch stop. Alternatively, etch stops may be made using pn junctions or other doping transitions, as is known in the art. Taking an SOI substrate as an example, an electrode is formed on the upper semiconductor layer (device layer) 53. The substrate 50 is formed on the bottom semiconductor layer (processed wafer). The aperture 51 can be made by any type of etching, such as dry etching and wet etching. One skilled in the art will know whether it is preferable to dope the silicon wafer with p-type or n-type. In order to prevent the generation of current in the free standing electrode, it is appropriate that there is no pn junction. As is known to those skilled in the art of etching and microfabrication, the doping level may be freely chosen.

  Suitably, the free standing electrode is provided with a coating 54. It has been found that the addition of a coating further improves the uniformity of the electric field. Various materials can be used to improve smoothness, including dielectric and conductive materials. However, metal coatings are considered the most appropriate. Contrary to dielectric material coatings, metal coatings do not add capacitance to the system. Processes for applying metal coatings, such as CVD, sputtering, electroplating, are known in the art. An adhesive layer may be used if desired. It is more appropriate not to oxidize the free-standing electrode semiconductor material before applying the metal coating. A metal coating may be applied simultaneously to the entire surface of the free-standing electrode, for example by a CVD process, but this is not considered essential. Instead, it may be coated from the bottom side and the top side, while any side is reliably covered at least partially by a conductive material. In such an embodiment, two different materials may be applied to the coating. Most preferably, the free standing electrode is completely conductive.

  Silicon is well known and well suited for the production of free-standing electrodes, but other materials and processes are not excluded. Such an alternative is to form a free-standing electrode on the substrate, for example as applied to RF MEMS applications, and in addition to Si-processed wafers, another substrate material comprising SiC and SiGe is used instead. Or in particular, including use as an upper layer.

  FIG. 6 shows a top view of a second embodiment according to the present invention. This embodiment shows a pair of electrodes 21, 22 that are alternately fitted. An edge zone 23 exists at the facing edge of the deflector 11. The edge zone 23 comprises a set of parallel strips of first and second electrodes 21, 22. However, the passing window 40 is not designed in the edge zone 23. It is appropriate that the strip design corresponds to the design of the main part of the deflector 9, but this is not essential. Although shown equally, the edge zone 23 can be well implemented with different designs.

  In addition to the edge zone 23 in a direction parallel to the electric field, it is advantageous to make the edge zone 26 in a direction perpendicular to the electric field, i.e. near the far end of the freestanding part of the electrode or strip. Such edge zones 26 help to prevent artifacts in the electric field as a result of substrate and / or conductor, eg, lead or interconnect interactions. Each of these edge zones preferably has an extension of 2 to 20%, more preferably 4 to 12% of the lateral extension of the strip 31.

  It is appropriate to assemble the deflector 11 of the present invention with the projection lens arrangement 12. This can be achieved without causing the significant electrostatic discharge problems observed with the prior art planar deflector shown in FIG. It has been found that deflectors with at least partially self-supporting electrode strips and a more uniform field are more resistant to electrostatic voltages. A deflector may be configured near the projection lens arrangement 12 or just above or below the projection lens arrangement 12.

  In one embodiment, the scanning deflector 11 of the present invention has the further advantage that its thickness is less than the thickness of prior art deflectors. In essence, the overall thickness of the substrate 50 and the electrode can be less than 500 micrometers, and preferably less than 300 micrometers. Thus, the scanning deflector 11 can be placed near the projection lens arrangement 12. Another configuration in which the scanning deflector 11 is close to the projection lens configuration 12 is not excluded. As a result of the short distance to the projection lens arrangement 12, the beamlet 7 deflected by the scanning deflector 11 has an effective center of rotation very close to the projection lens arrangement 12. As a result, the aberrations of the projection lens arrangement 12 do not significantly affect the pixel spot size.

  FIG. 7 shows a third embodiment according to the present invention. In this embodiment, the electrode system comprises several parts 91-94. In this example, the number is four, but need not be four, nor is it limited to four. As the number increases (eg, 9 or 16), this can be smaller (2). The electrode system can be subdivided into a series of adjacent portions rather than a plurality of blocks. Each of the portions comprises a continuous strip of electrodes 21, 22, which overlap the apertures 51 a-d in the substrate 50. In this embodiment, there are four apertures 51a-d, and the four apertures correspond to the four portions 91-94. However, this is not strictly required. The additional layer may serve as a support for the entire strip electrode system. This additional layer comprises apertures 51a-d and, on the other hand, overlaps the aperture 51 in the substrate 50. The apertures 51a-d need not have a cubic cross section. For example, the lateral extension may be larger than the width or vice versa. Suitably, the continuous strips in each of the parts form alternating mated pairs of electrodes, but this is not strictly necessary. Furthermore, the other features described above can be applied here to each of the four parts.

  FIG. 8 is a schematic diagram of an embodiment of the scanning electrostatic deflection system of the present invention. This embodiment includes a first electrostatic scanning deflector 11a and a second electrostatic scanning deflector 11b. According to the invention, at least one of the deflectors 11a, 11b is a deflector of the invention. It is appropriate that both are the scanning deflectors of the present invention. With this system design, even if the beamlet 7 is deflected, it is achieved that the beamlet 7 passes through the central part of the optical axis 0 in the effective lens surface 19 of the projection lens arrangement. In this way, the spherical aberration caused by deflection by the projection lens arrangement is even smaller compared to the arrangement with a single scanning deflector 11 of the present invention. An important improvement with this design is that while the amount of deflection that can be used is increased, the resolution of the spot size is not compromised. In this design shown in FIG. 8, the two deflectors 11a and 11b are arranged back and forth, each having a reverse voltage at the electrodes. In order to deflect, the sign of these voltages for each deflector 11a, 11b is switched simultaneously. By taking into account the distance d5 between the effective lens surface 19 of the projection lens system configuration and the deflector 11b, by finely adjusting the ratio of the deflection angles, the center of the deflection beamlet 7 on the effective lens surface 19 becomes the projection lens. Near the optical axis 0 of the system. In this fine adjustment operation, the mutual distance d6 between the two deflectors 11a and 11b and the potential difference applied between the electrodes may be further used. Here, the potential difference applied to the first scanning deflector 11a and the potential difference applied to the second scanning deflector 11b are coupled to each other. By changing these, the center point of the beamlet 7 intersects the optical axis 0 of the projection lens system on the optical surface of the projection lens configuration. In a suitable implementation, the drive circuits for the first and second deflectors 11a, 11b are controlled through a single controller. Furthermore, it is appropriate to integrate or otherwise combine parts of the drive circuit, for example the part that generates the scanning frequency.

  Accordingly, the first deflector 11a deflects the beamlet 7 from the optical axis 0 at an angle α1, and the second deflector 11b deflects the beamlet 7 to an original state in the opposite direction at an angle α2. Thus, when passing through the effective lens surface 19 of the projection lens configuration, the beamlet 7 is deflected over an angle α3.

  In yet another embodiment not shown in the figure, the aperture exists only under the passing window.

  In another aspect of the invention, a charged particle system is provided that includes a scanning electrostatic deflector that deflects at least one beamlet of charged particles. The deflector has first and second electrodes, the beamlet passes between the first and second electrodes, each electrode comprising at least one strip, A passage window extending substantially in parallel and through which a plurality of beamlets pass, the passage window having a width in a direction perpendicular to the strip, and setting a potential difference between the electrodes, An electric field is generated in a direction perpendicular to the strip, said strip having three mutually perpendicular directions, height, width and lateral direction, the height of the strip being greater than the width of the passage window. Is also big.

  Using this deflector, a deflection angle of the same order as a macroscopic deflector operating with a much larger potential difference was obtained. This is surprising because the ratio of the potential difference between the prior art macroscopic deflector and the deflector of the present invention can exceed 5, even even 10. Furthermore, as the height increases, the stray component of the electric field decreases, which improves the field linearity and deflection uniformity. Furthermore, it can be seen that the overall thickness of the deflector is small compared to the macroscopic deflector. As a result, the deflector of the present invention can be more easily assembled with the projection lens configuration to reduce aberrations.

  Suitably the deflector comprises a free-standing electrode strip.

  In another aspect of the invention, a method for scanning a surface at a scanning frequency using an electrostatic deflector is provided. The deflector includes first and second deflectors, and a passing window exists between the first and second deflectors. Here, each beamlet scans one line on the surface in one scanning period. Scanning includes positioning the beamlet at the starting position during the positioning period and deflecting the beamlet from the starting position by changing the strength of the electric field on the electrode during the writing period. According to the present invention, the scanning frequency is in the radio frequency (RF) range. In each scanning period, the beamlet is deflected in the same direction. Under the action of an electric field, the orientation of each beamlet is determined and each beamlet is deflected. Further, the positioning period is shorter than the writing period.

  The present invention can scan effectively with different regulation schemes with different rules than the prior art. This regulation system relates to high frequency scanning. More specifically, the high scanning frequency is most preferably a frequency in the range of radio frequency (RF) and in the middle of 300 to 3000 kHz. As a result, it must be deflected to comply with the rules of the RF electronics to prevent delays and non-uniformities due to the required material and conductor RF behavior. One significant RF characteristic is parasitic capacitance. In particular, parasitic capacitance can introduce significant delays when changing the voltage and reversing. In addition, parasitic capacitance tends to distort the field and make the scan more likely to be out of specification.

  Therefore, the problem identified by the inventors of the present invention was how to scan a pattern at a sufficient speed without causing problems with the accuracy of the transferred pattern.

  Here, the inventor of the present invention proposed to deflect the beamlet by a relatively small angle and scan only within the radio frequency range. If the deflection angle is made smaller in this way, the accuracy is improved and the applied voltage difference with respect to the electrode of the deflector can be reduced. Furthermore, it has been found that in order to obtain appropriate and reliable results for such high frequency scans, the deflection is limited to one orientation. Such deflection of one orientation requires further repositioning of the beamlet and is costly and time consuming. However, it has been found that when deflected in the opposite orientation, there is a difference in the surface area of the beamlet grid between the deflected and non-deflected situations. At high frequencies, it was thought that such differences in the surface area could not be corrected. The inventor of the present invention thought that by suppressing the parasitic capacitance, the time taken to reposition the beamlet is significantly reduced. At the same time, it has been found that suppressing the parasitic capacitance in this way reduces field distortion and further improves scanning accuracy.

  In short, our inventor's solution for accurately scanning a pattern at a sufficient speed is to reduce the time it takes to reposition a high frequency scan in only one orientation by reducing parasitic capacitance. Including the combination.

  In one suitable embodiment, the voltage is applied to the electrode of the deflector due to the sawtooth characteristics. The exact sawtooth shape may be adjusted to optimize performance. Note that setting the voltage in reverse provides the desired repositioning and mechanical repositioning of the target with respect to the lithography system. This is done simultaneously.

  In a further embodiment, the positioning time is shortened by filtering and / or weakening the parasitic capacitance. By adding components to the deflector and performing filtering, such filtering is appropriately performed. Those skilled in the art of analog electronics will know the topology of the filter. For example, an RC filter, an RLC filter, a pie filter, an LC filter, and a network are included. It is most appropriate to use an RC filter. This can be done through a termination resistor.

  In yet another embodiment, the voltage applied to the electrode of the deflector is less than 10V. This voltage reduction is particularly suitable in order to reduce the power loss as a result of the filtering. As a deflector operating with a small potential difference, it is most appropriate to use the deflector of the present invention. In addition, the deflector uses free standing electrodes to further reduce the parasitic capacitance of the deflector, thus assisting in the reduction.

  Suitably, the positioning period has a duration that is approximately half of the writing period. More suitably, the positioning period has a duration of less than 40% of the writing period, and most preferably has a duration of less than 25%.

In addition to the claims, the present invention further relates to details and aspects that are only apparent in the figures, in addition to the foregoing description and introduction. However, those skilled in the art can directly and clearly derive the details and aspects that are only apparent in the figures.
The invention described in the scope of claims at the time of filing the present application will be appended.
[1] A charged particle optical system comprising: a beamlet generator for generating a plurality of beamlets of charged particles; and an electrostatic deflector for deflecting the beamlets,
The electrostatic deflector includes first and second electrodes, and the first and second electrodes are used to generate an electric field for deflecting the beamlet between the first and second electrodes. The electrodes are configured to be connected to a voltage, and the first and second electrodes are at least partially self-supporting in an active area of the electrostatic deflector;
The first electrode comprises first and third strips, the second electrode comprises second and fourth strips;
The first and second electrodes define a passing window for passing at least a portion of the beamlet between the first and second electrodes, and the orientation of the electric field in each passing window is the same;
A passing window exists between the first and second strips and between the third and fourth strips, the passing window having a length in the first direction and a width in the intersecting direction. Have
The charged particle optical system is configured to position the beamlets in at least two rows and to direct one row of the beamlets through each passing window of the electrostatic deflector. The beamlets in the row extend in the first direction;
A substantial portion of the electrostatic deflector extends beyond the passage window in the first direction;
Charged particle optics system.
[2] The beamlets forming the row are arranged with a pitch between the beamlets;
The substantial portion of the electrostatic deflector extends beyond the passing window in the first direction by at least the pitch of the beamlet in the passing window. Charged particle optics system.
[3] The charged particle optical system according to [1], wherein the electrostatic deflector deflects the beamlet so as to intersect the first direction.
[4] The charged particle optical system according to [3], wherein the electrostatic deflector is a scanning deflector that performs final writing projection of the charged particle optical system.
[5] Each passing window has a width in a direction perpendicular to the first to fourth strips,
When a potential difference is set between the first and second electrodes, an electric field is generated in a direction perpendicular to the first to fourth strips,
The first to fourth strips have three directions perpendicular to each other, and have a height, a width, and a lateral direction;
The charged particle optical system according to [1], wherein the height of the first to fourth strips is larger than the width of the passage window.
[6] The charged particle optical system according to [1], wherein there is no passage window in a region between the second and third strips.
[7] The charged particle optical system according to [6], wherein the region is included as a free space.
[8] Each first and second electrode comprises a plurality of strips extending in parallel;
The charged particle optical system according to [7], wherein the strips of the first and second electrodes constitute a pair of alternately fitted electrodes.
[9] The charged particle optical system according to [8], wherein a plurality of passage windows exist between the alternately fitted electrodes.
[10] The charged particle optical system according to [1], wherein the electric field between the first and second electrodes is less than 100V.
[11] The charged particle optical system according to [10], wherein the electric field between the first and second electrodes is less than 20V.
[12] The electrostatic deflector includes an edge zone at an edge of the active area in a second direction orthogonal to the first direction,
The charged particle optical system according to [1], wherein the edge zone includes a strip of the electrode and defines an electric field in the same orientation as the electric field, but has no beamlet passage window.
[13] A second electrostatic deflector further included upstream or downstream of the first electrostatic deflector,
The charged particle optical system according to [1], wherein the second electrostatic deflector deflects the beamlet in a direction or orientation different from that of the first electrostatic deflector.
[14] The charged particle optical system according to [1], wherein the first and second electrodes that are free-standing are covered with a coating so as to provide an electrically substantially uniform surface.
[15] The charged particle optical system according to [14], wherein the coating is a metal coating.
[16] The charged particle optical system according to [1], wherein a termination resistor exists.
[17] The charged particle optical system according to [1], wherein there are mechanical struts in or overlapping the aperture to mechanically support at least one electrode or strip.
[18] The method for using the charged particle optical system according to [1], wherein at least one beamlet of the charged particles is deflected.
[19] The method according to [18], further comprising supplying a voltage having opposite polarity to the first and second electrodes.
[20] The method according to [18], wherein the voltages having opposite polarities are equal in magnitude and less than 10V.
[21] The method according to [19] or [20], wherein the voltage is supplied at a frequency in a range of 0 to 10 MHz.
[22] The method according to [18], wherein the beamlet is positioned at a start position in a positioning period and is deflected from the start position in a writing period.
[23]-The scanning frequency is in the radio frequency (RF) range;
In each scanning period, the beamlets are deflected in the same orientation;
Each beamlet is deflected under the action of the electric field oriented equally to each beamlet;
-The method according to [22], wherein the positioning period is shorter than the writing period.
[24] A method of projecting a predetermined pattern onto a target surface by a maskless lithography system comprising:
a. Generating a plurality of beamlets;
b. Modulating a beamlet using modulation means supplied with data of the predetermined pattern retrieved from a data storage device;
c. Focusing the modulated beamlet onto the target surface using focusing means;
d. Scanning the predetermined pattern on the target surface by deflecting the modulated beamlets with static electricity;
Including
The method wherein the scanning step is performed as described in any one of [18] to [23].

  DESCRIPTION OF SYMBOLS 0 ... Optical axis, 1 ... Lithography system, 3 ... Electron source, 4 ... Beam, 5 ... Collimating optical system represented by lens, 6 ... Beam splitter, 7 ... Beamlet, 8 ... Modulator unit, 9 ... Beam blanker array 10 ... Beamlet stop array, 11 ... Electrostatic scanning deflector array, 12 ... Projection lens, 13. ..Target surface, 14 ... light, 15 ... plate, 16 ... actuator, 17 ... unit, 18 ... electro-optic unit, 19 ... lens surface, 20 ... active area , 21 ... 1st electrode, 22 ... 2nd electrode, 23 ... Edge zone, 24 ... Target, 25 ... Ground electrode, 26 ... Edge zone, 28 ... Bondpa 29 ... Interconnection part, 31-38 ... Strip, 40 ... Passing window, 41 ... Insulating window, 50 ... Substrate, 51, 51a-d ... Aperture, 52 ..Embedded oxide layer, 53 ... treated wafer, 54 ... metal coating, 60 ... control unit, 61 ... data storage device, 62 ... reading unit, 63 ... data Transducer, 64 ... optical fiber, 65 ... projector, 91-94 ... part, 101 ... first side, 102 ... second side, 131, 132, 133 (Prior art) strips, a ... width of the passage window 40, b ... width of the strip 31, c ... width of the insulating window 41, z ... height of the strip.

Claims (24)

A charged particle optical system comprising: a beamlet generator that generates a plurality of beamlets of charged particles; and an electrostatic deflector that deflects the beamlets,
The electrostatic deflector includes first and second electrodes, and an electric field for deflecting the beamlet is mainly determined by a side surface of the first electrode and a side surface of the second electrode . The first and second electrodes are configured to be connected to a voltage for generating between the two electrodes, and the first and second electrodes are connected to the first of the electrostatic deflector . Being at least partially self-supporting in an active area formed by a side surface of one electrode and a side surface of a second electrode ;
The first electrode comprises first and third strips, the second electrode comprises second and fourth strips;
The first and second electrodes define a passing window for passing at least a portion of the beamlet between the first and second electrodes, and the orientation of the electric field in each passing window is the same;
A passing window exists between the first and second strips and between the third and fourth strips, the passing window having a length in the first direction and a width in the intersecting direction. Have
The charged particle optical system is configured to position the beamlets in at least two rows and to direct one row of the beamlets through each passing window of the electrostatic deflector. The beamlets in the row extend in the first direction;
The electrostatic deflector, the passage beyond the window in the first direction extends outside of the active area,
Charged particle optics system. The beamlets in the rows are arranged with a pitch between each beamlet;
The electrostatic deflector, said at least the pitch of the beamlets in the pass window, extends outside of the active area beyond the passage window in the first direction, according to claim 1 Charged particle optics system.   The charged particle optical system according to claim 1, wherein the electrostatic deflector deflects the beamlet so as to intersect the first direction.   The charged particle optical system according to claim 3, wherein the electrostatic deflector is a scanning deflector that performs final writing projection of the charged particle optical system. Each passing window has a width in a direction perpendicular to the first to fourth strips,
When a potential difference is set between the first and second electrodes, an electric field is generated in a direction perpendicular to the first to fourth strips,
The first to fourth strips have three directions perpendicular to each other, and have a height, a width, and a lateral direction;
The charged particle optical system according to claim 1, wherein the height of the first to fourth strips is larger than the width of the passage window.   The charged particle optical system according to claim 1, wherein a region between the second and third strips has no passing window.   The charged particle optical system according to claim 6, wherein the region is included as a free space. Each first and second electrode comprises a plurality of strips extending in parallel,
The charged particle optical system according to claim 7, wherein the strips of the first and second electrodes constitute an alternating pair of electrodes.   The charged particle optical system according to claim 8, wherein a plurality of passing windows exist between the alternately fitted electrodes.   The charged particle optical system of claim 1, wherein the electric field between the first and second electrodes is less than 100V.   The charged particle optical system of claim 10, wherein the electric field between the first and second electrodes is less than 20V. The electrostatic deflector includes an edge zone at an edge of the active area in a second direction orthogonal to the first direction;
The charged particle optical system of claim 1, wherein the edge zone comprises a strip of the electrode and defines an electric field in the same orientation as the electric field, but no beamlet passage window. A second electrostatic deflector included upstream or downstream of the first electrostatic deflector;
The charged particle optical system according to claim 1, wherein the second electrostatic deflector deflects the beamlet in a direction or orientation different from that of the first electrostatic deflector.   The charged particle optical system of claim 1, wherein the freestanding first and second electrodes are covered with a coating to provide an electrically substantially uniform surface.   The charged particle optical system of claim 14, wherein the coating is a metal coating.   The charged particle optical system of claim 1, wherein a termination resistor is present.   The charged particle optical system of claim 1, wherein mechanical struts are present in or overlying the aperture to mechanically support at least one electrode or strip.   The method of using a charged particle optical system according to claim 1, wherein at least one beamlet of charged particles is deflected.   19. The method of use according to claim 18, comprising supplying voltages of opposite polarity to the first and second electrodes.   19. Use according to claim 18, wherein the voltages of opposite polarity are of equal magnitude and less than 10V.   21. A method according to claim 19 or 20, wherein the voltage is supplied at a frequency in the range of 0 to 10 MHz.   The method according to claim 18, wherein the beamlet is positioned at a start position during a positioning period and is deflected from the start position during a writing period. The scanning frequency is in the radio frequency (RF) range;
In each scanning period, the beamlets are deflected in the same orientation;
Each beamlet is deflected under the action of the electric field oriented equally to each beamlet;
The method according to claim 22, wherein the positioning period is shorter than the writing period. A method of projecting a predetermined pattern onto a target surface by a maskless lithography system, comprising:
a. Generating a plurality of beamlets;
b. Modulating a beamlet using modulation means supplied with data of the predetermined pattern retrieved from a data storage device;
c. Focusing the modulated beamlet onto the target surface using focusing means;
d. Scanning the predetermined pattern on the target surface by deflecting the modulated beamlets with static electricity;
Including
24. A method, wherein the scanning step is performed as described in any one of claims 18-23.

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