Modulation device and power supply arrangement

The invention relates to a modulation device for modulating charged particle beamlets in accordance with pattern data in a multi-beamlet charged particle lithography system. The device comprises a plate-like body, an array of beamlet deflectors, a plurality of power supply terminals (202-205) for supplying at least two different voltages, a plurality of control circuits, and a conductive slab (201) for supplying electrical power to one or more of the power supply terminals (202-205). The plate-like body is divided into an elongated beam area (51) and an elongated non-beam area (52) positioned with their long edges adjacent to each other. The beamlet deflectors are located in the beam area. The control circuits are located in non-beam area. The conductive slab is connected to the control circuits in the non-beam area. The conductive slab comprises a plurality of thin conductive plates (202-205).

FIELD OF THE INVENTION

The invention relates generally to lithography systems, and more particularly, to a charged particle beamlet modulation device and a power supply system for a beamlet modulation device.

BACKGROUND OF THE INVENTION

Charged particle lithography systems are known in the art, for example from U.S. Pat. No. 6,958,804 in the name of the applicant. This lithography system uses a plurality of electron beamlets to transfer a pattern to the target surface. The pattern data is sent to a modulation device, also referred to as a beamlet blanker array. Herein, the beamlets are modulated, for example by electrostatic deflection of the beamlets to switch selected beamlets on or off. The modulated beamlets are projected onto the surface of a target to be exposed. To enable high speed transfer of the pattern to the target surface, optical transmission of control signals to the modulation device may be used.

To manufacture lithography systems able to perform exposures having smaller critical pattern dimensions with sufficiently high throughput, charged particle systems have been proposed having a very large number of charged particle beamlets. The number of beams in a charged particle system suitable for smaller critical dimensions may be in the order of tens or hundreds of thousands or millions.

For lithography purposes the area in which final projection occurs is typically limited to a single field, and in a charged particle system where the beamlets remain substantially parallel this results in the area of the modulation device being limited to about 27×27 mm. The electrical power requirements of the modulation device are substantial, and the electrical current flowing in the modulation device will generate magnetic fields. In such a small area, the effect of these magnetic fields becomes significant. Any magnetic fields in the area of the modulation device will exert a deflecting force on the electron beamlets passing through the device, and even very small deflections of the beamlets may result in writing errors on the target.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to reduce the effect of unwanted magnetic fields due to electrical currents flowing in a beamlet modulation device. The invention is defined by the independent claims. The dependent claims defined advantageous embodiments. Accordingly, the invention relates to a modulation device and to a charged particle lithography system, and to a power supply arrangement, according to the appended claims.

In a first aspect the invention relates to modulation device for use in a charged particle lithography system (100) adapted to generate charged particle beamlets (123). The modulation device is arranged for modulating the charged particle beamlets in accordance with pattern data and comprises: i) a plate-like body (106); ii) an array of beamlet deflectors (30) arranged on the plate-like body (106) for deflecting the beamlets; iii) a plurality of power supply terminals (202-205) for supplying at least two different voltages; iv) a plurality of control circuits (40,41) arranged on the plate-like body (106) to receive the pattern data and supply corresponding control signals to the beamlet deflectors (30), wherein the control circuits (40,41) are fed by the plurality of power supply terminals (202-205); and v) a conductive slab (201) arranged to supply electrical power to the power supply terminals (202-205). Furthermore, the body of the modulation device is divided into an elongated beam area (51) and an elongated non-beam area (52) positioned adjacent to the beam area (51) so that a long edge of the beam area (51) borders a long edge of an adjacent non-beam area (52). The beamlet deflectors are arranged in the beam area (51). The control circuits (40,41) are located in the non-beam area (52) for providing control signals to the beamlet deflectors (30). The conductive slab (201) is connected to the control circuits (40,41) in the non-beam area (52), the conductive slab (201) comprising a plurality of thin conductive plates (202-205), wherein the conductive slabs (201) forms part of the power supply arrangement. The beamlet deflectors and the control circuit arranged ‘on’ the plate-like body does not mean that they need to be exactly arranged only on the surface of the plate-like body. A portion of, or the whole of, the deflector and the control circuit may also be arranged in the plate-like body.

The power supply arrangement provides relatively a short power supply line to the control circuits and beamlet deflectors. A conductive slab (or conducting slab) comprising a plurality of thin conductive (or conducting) plates (preferably but not necessarily each plate connecting to a different power supply terminal) may be connected to the control circuits of the modulation device along all or a majority of the length of the slab, so that the conductive lines connecting the power supply to the control circuits and beamlet deflectors run in a direction substantially perpendicular to the face of the conductive slabs to minimize their length. Consequently, the magnetic field created by these interconnection lines can be minimized. A reduction in magnetic fields is achieved by a specific configuration of the conductive slab, which is composed by a number of thin conductive plates arranged in parallel.

An embodiment of the modulation device comprises a plurality of conductive slabs arranged to supply electrical power to the power supply terminals. The body of the modulation device is divided into a plurality of elongated beam areas and a plurality of elongated non-beam areas positioned adjacent to the beam areas so that a long edge of each beam area borders a long edge of an adjacent non-beam area. The beamlet deflectors are arranged in groups, each group of beamlet deflectors located in one of the beam areas. The control circuits are located in the non-beam areas for providing control signals to the beamlet deflectors. Each control circuit is located in one of the non-beam areas adjacent to one of the beam areas containing one or more of the beamlet deflectors receiving control signals from the control circuit. Furthermore, the conductive slabs are connected to the control circuits in the non-beam areas, each conductive slab comprising a plurality of thin conductive plates, wherein the plurality of conductive slabs forms part of the power supply arrangement. The advantage of this alternating modulation device design is that that the modulation device can be made larger (i.e. increasing the writing capacity of the charged particle lithography system), while maintaining short and low-impedance connections to the power supply terminals.

In an embodiment of the modulation device each thin conductive plate is configured for connecting to a respective one of the power supply terminals. This is particularly advantageous in case the control circuits have multiple power supply terminals having different supply voltages.

In an embodiment of the modulation device each of the conductive plates of one of the conductive slabs has a face terminating in one or more edges, and the plates are arranged with their faces substantially parallel to each other. A first effect is that the plates act as shielding plates for each other. Furthermore, such configuration allows for current-return paths which are nearby such that current loops can be kept small. This results in small inductances of the power supply lines, which is beneficial for power supply noise.

In an embodiment of the modulation device the face of each of the conductive plates of one of the conductive slabs is substantially equal in area. The advantage of this embodiment is that the shielding effect is enhanced, i.e. none of the plates extends beyond the other plates.

In an embodiment of the modulation device each of the conductive plates has a substantially uniform thickness. This also results in a uniform resistance and a uniform maximum current capacity of the plates.

In an embodiment of the modulation device a ratio of thickness of one of the conductive plates and a square root of the area of the face of the plate is less than 0.01. This configuration leads to a very good electrical performance in terms of low power supply resistance of the power supply connections.

In an embodiment of the modulation device each conductive plate of one of the conductive slabs has substantially the same resistivity relative to the other conductive plates of the conductive slab. This thicker conductive slab may be advantageously chosen to be the common power supply terminal, i.e. the electrical ground terminal, which acts as current-return path for all power supply terminals.

In an embodiment of the modulation device each conductive plate of one of the conductive slabs has substantially the same resistivity at every position over its extent relative to the other conductive plates of the conductive slab. Such configuration has the advantage that the power supply potentials are best defined (less susceptible to process and design variations).

In an embodiment of the modulation device at least one edge of each conductive plate is adapted for connection to a power supply and at least one different edge of each plate is adapted for connection to a plurality of the control circuits. In this embodiment the plurality of conductive plates in the conductive slabs can be coupled to the power supply, which may be conveniently integrated on a different substrate or plate.

In an embodiment of the modulation device the control circuits are distributed along substantially all of the length of the long edge of a non-beam area which borders the long edge of an adjacent beam area. This configuration leads to the shortest connections between the control circuits and the beamlet deflectors inside the beam area.

In an embodiment of the modulation device the connections between one of the conductive slabs and the control circuits in a non-beam area are distributed along substantially all of the length of the long edge of a non-beam area which borders the long edge of an adjacent beam area. This results in the best current distribution and is advantageous as it keeps parasitic inductances low.

In an embodiment of the modulation device the connections between the conductive slabs and the control circuits are made via a plurality of conductive bumps or solder joints on a surface of the body of the modulation device. This is a convenient way of forming the connections.

In an embodiment of the modulation device the conductive slabs comprise a first portion with a face parallel to the surface of the body where the bumps are located, and a larger second portion substantially perpendicular to the surface of the body. Such configuration eases the use of bumps to form the connections.

In an embodiment of the modulation device a first plurality of the conductive bumps or solder joints connect with a first one of the conductive plates of a conductive slab, and a second plurality of the conductive bumps connect with a second one of the conductive plates of the conductive slab.

In an embodiment of the modulation device at least one of the conductive slabs comprises a plurality of conductive plates arranged to conduct forward electrical current from a power supply to the control circuits and beamlet deflectors, and at least one conductive plate arranged to conduct return electrical current from the control circuits and beamlet deflectors to the power supply, wherein the forward electrical current is substantially equal to the return electrical current. Such configuration is advantageous for keeping the current loops small and parasitic inductances low. The conductive plates of each slab are preferably manufactured to have the same dimensions and the same resistivity. The forward and return electrical current through the conductive plates of each slab is preferably equal. Due to the shape of the plates, their uniform resistivity, and the very short separation between the plates, the parallel plates can approximately be considered as parallel infinite current sheets. Moreover, because the current flowing to the modulation device equals the return current flowing back to the power supply, the total sum of the linear current density on the conductive plates of each slab is close to zero. In a first order approximation, the magnetic field generated by a conductive slab is close to zero everywhere, except in the area between the conductive plates, so that a very good magnetic field cancellation can be established.

In an embodiment of the modulation device a ratio of the sum of the thickness of the plates which conduct forward electrical current and the sum of the thickness of the plates which conduct return electrical current is between 0.7 and 1.3, and preferably about 1.0. This configuration ensures that the current densities are uniform and thus also thermal effects (heating due to current flow) are more uniform.

In an embodiment of the modulation device a ratio of the distance between two adjacent conductive plates of one of the conductive slabs and the square root of the area of the face of the adjacent plates is less than 0.01. This configuration leads to a very good electrical performance in terms of low power parasitic inductance of the power supply connections.

In an embodiment of the modulation device the conductive slabs further comprise electrical insulation layers sandwiched between the conductive plates. One of the advantages of this embodiment is that the electrical insulating layers provide for mechanical stability of the conductive slabs.

In an embodiment of the modulation device the conductive slabs are rectangular, having two equal long edges and two equal short edges. This embodiment leads to a simple design ensuring a low impedance of the power supply connections.

In an embodiment of the modulation device the conductive lines from the plates to the light sensitive elements and the return lines are substantially perpendicular to the face of the plates.

In an embodiment of the modulation device the beam areas have a length and a width, the length being at least five times the width. This embodiment leads to a simple design ensuring a low impedance of the power supply connections.

In an embodiment of the modulation device the beam areas have a length and a width, the length being at least ten times the width. This embodiment leads to a simple design ensuring an even lower impedance of the power supply connections.

In an embodiment of the modulation device the beamlet deflectors arranged in two-dimensional arrays in the beam areas, each deflector provided with electrodes extending on opposing sides of an aperture for generating a voltage difference across the aperture. This configuration provides for a simple and compact array of beamlet deflectors.

In an embodiment of the modulation device the control circuits comprise a plurality of light sensitive elements arranged to receive modulated optical signals carrying the pattern data and converting the optical signals into electrical control signals for control of the beamlet deflectors. Receiving the signals in the modulation device optically has as great advantage that a vacuum barrier may be easily crossed without disturbing the vacuum, i.e. through a window or an optical fiber crossing the vacuum barrier.

In an embodiment of the modulation device the control circuits further comprise a plurality of demultiplexers, each demultiplexer arranged to receive a control signal from a corresponding one of the light sensitive elements, and demultiplex the control signal to generate a plurality of control signals to control a plurality of beamlet deflectors. In case optical fibers are used to transmit the signals to the manipulator optically, the bandwidth which is available is very large. Such bandwidth opens up the opportunity to share such optical fiber connection between multiple beamlet deflectors. An optical fiber has a certain dimension and thus costs space in a lithography apparatus. This is why the embodiment as here described is very convenient (enables maximum resource sharing while maintaining enough bandwidth).

In a second aspect the invention further relates to a charged particle lithography system comprising: i) a beam generator arranged for generating a plurality of charged particle beamlets divided into separate groups; ii) a modulation device according to any one of the preceding claims; and iii) a projection system arranged for projecting the modulated beamlets onto a target to be exposed. Furthermore, each beam area of the modulation device is positioned in the path of one of the groups of beamlets and each non-beam area is positioned outside the path of the groups of beamlets. The charged particle lithography system of the invention conveniently benefits from the modulation device of the invention. Such system has analogous embodiments as the embodiments of the modulation device of the invention.

In a third aspect the invention also relates to a power supply arrangement for use in the charged particle lithography system of the invention. The power supply arrangement comprises: i) at least one input terminal for receiving at least one input voltage; ii) at least two output terminals for supplying at least two different output voltages; iii) at least one DC-DC converter coupled between the at least one input terminal and the at least two output terminals, the at least one DC-DC converter being configured for converting the at least one input voltage into the at least two different output voltages; and iv) a conductive slab coupled to the at least two output terminals, the conductive slab being configured for being coupled to the power supply terminals of the modulation device for supplying electrical power to the modulation device, the conductive slab comprising a plurality of thin conductive plates. As follows from the discussion of the earlier embodiments, the invention may be also embodied in a power supply arrangement on which the conductive slab or slab is formed, wherein the conductive slab is configured for being coupled to and supplying power to the modulation devices. Similarly, each conductive slab comprises a plurality of conductive plates as described by the modulation device according to the invention.

An embodiment of the power supply arrangement comprises a plurality of conductive slabs arranged to supply electrical power to the power supply terminals, each conductive slab comprising a plurality of thin conductive plates. The advantages and effects of this embodiment are similar to that of the corresponding embodiments of the modulation device.

In an embodiment of the power supply arrangement each thin conductive plate is configured for connecting to a respective one of the power supply terminals. The advantages and effects of this embodiment are similar to that of the corresponding embodiments of the modulation device.

The power supply arrangement according to the third aspect has the same embodiments as the modulation device according to the first aspect.

In a fourth aspect of the invention, the invention provides a modulation device for use in a charged particle lithography system adapted to generate a plurality of groups of charged particle beamlets, the modulation device arranged for modulating the charged particle beamlets in accordance with pattern data and comprising a plate-like body, an array of beamlet deflectors arranged for deflecting the beamlets, a plurality of control circuits arranged to receive the pattern data and supply corresponding control signals to the beamlet deflectors, and a plurality of conductive slabs arranged to supply electrical power to the control circuits and beamlet deflectors; wherein the body of the modulation device is divided into a plurality of elongated beam areas and a plurality of elongated non-beam areas positioned adjacent to the beam areas so that a long edge of each beam area borders a long edge of an adjacent non-beam area; wherein the beamlet deflectors are arranged in groups, each group of beamlet deflectors located in one of the beam areas; wherein the control circuits are located in the non-beam areas, each control circuit located in one of the non-beam areas adjacent to one of the beam areas containing one or more of the beamlet deflectors receiving control signals from the control circuit; and wherein the conductive slabs are connected to the control circuits in the non-beam areas, each conductive slabs comprising a plurality of thin conductive plates.

The modulation device according to the fourth aspect has the same embodiments as the modulation device according to the first aspect.

The power supply arrangement provides relatively short power supply lines to the control circuits and beamlet deflectors. Conductive slabs (or conducting slabs) comprising a plurality of thin conductive (or conducting) plates (each plate connecting to a different power supply terminal) may be connected to the control circuits of the modulation device along all or a majority of the length of the slab, so that the conductive lines connecting the power supply to the control circuits and beamlet deflectors run in a direction substantially perpendicular to the face of the conductive slabs to minimize their length. Consequently, the magnetic field created by these interconnection lines can be minimized.

A reduction in magnetic fields is achieved by a specific configuration of the conductive slabs, which are each composed by a number of thin conductive plates arranged in parallel. The conductive plates of each slab are preferably manufactured to have the same dimensions and the same resistivity. The forward and return electrical current through the conductive plates of each slab is preferably equal. Due to the shape of the plates, their uniform resistivity, and the very short separation between the plates, the parallel plates can approximately be considered as parallel infinite current sheets. Moreover, because the current flowing to the modulation device equals the return current flowing back to the power supply, the total sum of the linear current density on the conductive plates of each slab is close to zero. In a first order approximation, the magnetic field generated by a conductive slab is close to zero everywhere, except in the area between the conductive plates, so that a very good magnetic field cancelation can be established.

In an embodiment the power supply provided by each conductive slab is effectively isolated from the others, so that there is no undesirable current flowing between the conductive slabs through the modulation device. The features of this embodiment are applicable to all mentioned embodiments of the invention.

A fifth aspect of the invention relates to a conductive slab for electrically connecting a power source to a load. The conductive slab comprises a plurality of conductive plates. Each plate has a face terminating in one or more edges. Each conductive plate has a substantially uniform thickness, and is sufficiently thin. Preferably a ratio of the thickness of each plate and a square root of the area of the face of that plate is less than 0.01. The plates are arranged with their faces substantially parallel to each other.

The conductive slab of the fifth aspect of the invention may be arranged in any one of the first to the fourth aspect of the invention and may include one of more of the features of the conductive slab described in the first to fifth aspect of the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following is a description of certain embodiments of the invention, given by way of example only and with reference to the drawings. The drawings are not drawn to scale and merely intended for illustrative purposes. Equivalent elements in different drawings are referred to with same reference numerals.

FIG. 1shows the conceptual schematic drawing of a charged particle multi-beamlet lithography system100based upon an electron beam optical system without a common cross-over of all the electron beamlets. Such lithography systems are described for example in U.S. Pat. Nos. 6,897,458 and 6,958,804 and 7,019,908 and 7,084,414 and 7,129,502 and 8,089,056, U.S. patent application publication no. 2007/0064213 and 2009/0261267 and US 2011/0079739 and US 2012/0091358, which are all assigned to the owner of the present invention and are all hereby incorporated by reference in their entirety.

In the embodiment shown inFIG. 1, the lithography apparatus100comprises an electron-optical column having an electron source101for producing an expanding electron beam120. The expanding electron beam120is collimated by collimator lens system102. The collimated electron beam121impinges on an aperture array103, which blocks part of the beam to create a plurality of sub-beams122. A condenser lens array104is included behind aperture array103, for focusing the sub-beams122, e.g. towards a corresponding opening in the beam stop array108. The sub-beams122impinge a multi-aperture array105which blocks part of each sub-beam to create a plurality of beamlets123from each sub-beam122. In this example, the aperture array105produces three beamlets from each sub-beam, but in practice a much larger number of beamlets may be produced, e.g.49beamlets per sub-beam or more, so that the system generates a very large number of beamlets122, preferably about 10,000 to 1,000,000 beamlets.

The electron beamlets123pass through apertures in a beamlet blanker array106. The aperture array105may be integrated with the beamlet blanker array106, e.g. arranged close together or as a single unit. The beamlet blanker array106and beam stop array108operate together to modulate or switch beamlets on or off. The beam blanker array106includes a plurality of beamlet deflectors, which may be in the form of blanker electrodes positioned near each aperture of the array. By introducing a voltage across the blanker electrodes of an aperture, the beamlet or beamlets passing through the aperture may be slightly deflected. After passing through the beamlet blanker array, the beamlets123arrive at beam stop array108, which has a plurality of apertures positioned so that the undeflected beamlets pass through the beam stop array and deflected beamlets are blocked by the beam stop array (or vice versa). If beamlet blanker array106deflects a beamlet, it will not pass through the corresponding aperture in beam stop array108, but instead will be blocked. But if beamlet blanker array106does not deflect a beamlet, then it will pass through the corresponding aperture in beam stop array108, and through beam deflection array109and projection lens arrays110. Thus, the beamlet blanker array106and beam stop array108operate together to block or let pass the beamlets123.

Beam deflector array109provides for deflection of the beamlets124in the X and/or Y direction substantially perpendicular to the direction of the undeflected beamlets, to scan the beamlets across the surface of target or substrate130. Next, the beamlets124pass through projection lens arrays110and are projected onto the surface of substrate130. The projection lens arrangement preferably provides a demagnification of about 100 to 500 times. The beamlets124impinge on the surface of substrate130positioned on moveable stage132for carrying the substrate. For lithography applications, the substrate usually comprises a wafer provided with a charged-particle sensitive layer or resist layer.

A control unit140may be provided for providing signals for control of the beamlet blanker array106. The control unit140may comprise a data storage unit142, a processor unit143and data converter144. The control unit140may be located remote from the rest of the system, for example outside the inner part of a clean room. The control system may further be connected to an actuator system146for control of movement of the moveable stage132and scanning of the beamlets by the deflector array109. The control unit140may be arranged for processing pattern data to generate signals for control of the blanker electrodes. The pattern data may be converted to modulated light beams for transmission to the beamlet blanker array106using optical fibers, and the modulated light beams projected from optical fiber ends onto corresponding light sensitive elements located on the beamlet blanker array106. The light sensitive elements may be arranged to convert the light signals into electrical signals for control of the blanker electrodes.

The charged particle lithography apparatus100operates in a vacuum environment. A vacuum is desired to remove particles which may be ionized by the charged particle beams and become attracted to the source, may dissociate and be deposited onto the machine components, and may disperse the charged particle beams. A vacuum of at least 10−6bar is typically required. In order to maintain the vacuum environment, the charged particle lithography system is located in a vacuum chamber135. All of the major elements of the lithography apparatus100are preferably housed in a common vacuum chamber, including the charged particle source, projector system for projecting the beamlets onto the substrate, and the moveable stage.

FIG. 2shows a simplified block diagram illustrating the principal elements of a modular lithography apparatus500. The lithography apparatus500is preferably designed in a modular fashion to permit ease of maintenance. Major subsystems are preferably constructed in self-contained and removable modules, so that they can be removed from the lithography apparatus with as little disturbance to other subsystems as possible. This is particularly advantageous for a lithography machine enclosed in a vacuum chamber, where access to the machine is limited. Thus, a faulty subsystem can be removed and replaced quickly, without unnecessarily disconnecting or disturbing other systems.

In the embodiment shown inFIG. 2, these modular subsystems include an illumination optics module501including the charged particle beam source101and beam collimating system102, an aperture array and condenser lens module502including aperture array103and condenser lens array104, a beam switching module503including the multi-aperture array105and beamlet blanker array106, and projection optics module504including beam stop array108, beam deflector array109, and projection lens arrays110. The modules are designed to slide in and out from an alignment frame. In the embodiment shown inFIG. 2, the alignment frame comprises an alignment inner subframe505and an alignment outer subframe506. A frame508supports the alignment subframes505and506via vibration damping mounts507. The substrate130rests on substrate support structure509, which is in turn placed on a chuck510. The chuck510sits on the stage short stroke511and long stroke512. The lithography apparatus is enclosed in vacuum chamber135, which may include a mu metal shielding layer or layers515, and rests on base plate520supported by frame members521.

It goes without saying that the beamlet blanker array106cannot function without a power supply. When beamlet blanker array106is connected to a power supply and operates, electrical current flows through the power supply, the connection wires between the power supply and the circuits on the beamlet blanker array, and the circuits and conductive elements on the substrate of the beamlet blanker array. These electrical currents will all generate magnetic fields, which may cause undesirable deflection of the electron beamlets and introduce errors into the exposure performed by the lithography system. As will be seen, the present invention aims to effectively reduce these magnetic fields so that operation of the lithography system can be optimized.

FIG. 3shows a simplified schematic view of an interconnection structure of the beamlet blanker array106and the power supply in one embodiment of the invention. The power supply comprises a number of power slabs201in the form of thin conductive plates, a common power unit300, and a number of power supply connections301. In the embodiment shown, there are six power slabs201. Each power slab201takes the form of a thin rectangle plate, with a large face terminating at thin edges, and having a long edge and a short edge as can be seen more clearly inFIGS. 6 and 7, although other shapes may also be used. The power slabs201are oriented substantially perpendicular to the surface of the blanker array106(i.e. with the face of the power slab perpendicular or nearly perpendicular to the surface of the blanker array), having one of the long edges parallel to the surface of the blanker array106for making connections thereto, and one of the short edges perpendicular to (or at an angle to) the surface of the blanker array106for making connections to the power unit300via power supply connectors301. Instead of a rectangular structure, the slab may have a fixed width throughout the trajectory between the side at which connection is made with the blanker array106and the side connected to the power unit300. It can be readily understood, that instead of a slab, in this case a ribbon cable, i.e. a ribbon comprising a plurality of parallel conductors, may be used as well.

FIG. 3also shows the subdivision of the beamlet blanker array106into beam areas51and non-beam areas52. The electron beamlets123are directed onto the beam areas51of the beamlet blanker array106by the upstream elements of the lithography system. A beam area51includes the apertures (holes in the beamlet blanker array substrate) through which the electron beamlets123pass, the blanker electrodes positioned adjacent to the apertures for deflecting the electron beamlets123, and conductive lines connecting the blanker electrodes to circuits for energizing the blanker electrodes. A non-beam area52, on the other hand, is positioned outside the normal path of the beamlets123, and includes circuits for control of the blanker electrodes located in the adjacent beam areas51. A non-beam area52may include light sensitive elements such as photo-diodes for receiving modulated optical signals carrying the pattern data and converting the optical signals into electrical signals for control the beamlet deflectors. Optical fibers for guiding the modulated optical signals towards the light sensitive elements may also be routed in the non-beam areas to avoid interfering with the beamlets123. Power slabs201are also positioned in the non-beam areas to avoid interfering with the beamlets123and the connections between the power slabs and the circuits on the beamlet blanker array106are also made in the non-beam areas52.

In one embodiment, blanker array106typically has a length L in a direction parallel to the power slabs201of between 15 and 35 mm, for example about 33 mm, and a width W in a direction perpendicular to the power slabs of between 10 and 50 mm. In one embodiment, the active area of the blanker array106(e.g. encompassing all the beam areas51) is in the form of square of 33 mm×30 mm. The width of a beam area51can be varied to an appropriate value, for example in a range between 0.1 and 5 mm. In one embodiment, the width of the beam areas51and non-beam areas52is about 2.0 mm.

In one embodiment, as shown inFIG. 3, each beam area51may be served by two adjacent non-beam areas52. Thus, the beamlet deflectors in a beam area are controlled by signals received by light sensitive elements in the non-beam areas located on both sides of the beam area. Moreover, for each beam area51, electrical power is supplied by the two adjacent power slabs201connected to the non-beam areas on either side of the beam area.

FIG. 4schematically shows a top view of a more detailed lay-out of a portion of a beamlet blanker array showing a single beam area51. The beamlet blanker array further includes a non-beam area52on each side of the beam area and containing the electrical circuits and components responsible for controlling the deflection of the beamlets123which pass through the beam area. In this embodiment, the non-beam areas52effectively cover all the surface area of the beamlet blanker array106that is not reserved for the beam area. Power is supplied by two power slabs201connected to the non-beam area52.

The non-beam areas52include an optical interface area53and a power interface area55, and may further include an additional interface area57. The optical interface area53is reserved for establishing an optical interface between a plurality of optical fibers and light sensitive elements on the beamlet blanker array. The optical fibers are arranged for guiding the modulated light beams towards the light sensitive elements placed within the optical interface area53. The optical fibers are suitably arranged so that they do not physically block electron beamlets within the beam area51during use of the lithography system, e.g. as shown inFIG. 6b.

In one embodiment, the optical interface area53is a long rectangular area (e.g. 33 mm×2.0 mm). One long edge of the optical interface area53is the boundary with the beam area51. The beamlet deflectors30in the beam area51are distributed along the length of the beam area. The light sensitive elements are preferably distributed along the length of the optical interface area53so that each light sensitive element is located close to the beamlet deflector(s)30in the beam area51which are controlled by signals from the light sensitive element. The other long edge of the optical interface area53is the boundary with the power interface area55where the power slab201is connected.

The power interface area55is arranged to accommodate a power arrangement for suitably powering the light sensitive elements and other components within the optical interface area53, and the beamlet deflectors30in the beam area51. As also shown inFIG. 3, the power slabs201extend in a direction substantially perpendicular to, and away from the blanker array. This arrangement enables the spread of the power lines over a large surface area, which improves the efficiency and reduces losses, e.g. due to a reduced thermal resistance caused by an increased radiation surface area.

Electrical connections between the power slabs201and the circuits on the beamlet blanker array106are preferably distributed along the length of a long edge of the power slabs. The position of the power slabs201on the sides of the optical interface area53enables the use of relatively short power supply lines from each power slab to adjacent light sensitive elements and other circuits required for driving the blanker electrodes30.

The arrangement of an elongated beam area51containing beamlet deflectors30distributed along its length, adjacent elongated optical interface areas53containing light sensitive elements40distributed along their length, and elongated power interface areas55adjacent to the optical interface areas53containing electrical connections to elongated power slabs201distributed along their length, combines to reduce the distance from a power slab to the beamlet deflector powered by that power slab. The conductive power supply lines from the power slab to the light sensitive elements and other circuits for driving the beamlet deflectors, and the return (power supply common) lines, can be arranged substantially perpendicular to the long edge of the power slabs, to minimize the distance of these conductive lines. Consequently, the magnetic fields created by these conductive lines can be minimized. Furthermore, variations in voltage drop between different power supply lines can also be reduced by reducing the variation in length of the lines, e.g. connections to light sensitive elements closer to a power slab versus connections to light sensitive elements further away. In the above-mentioned embodiment, the optical interface area53is a long, thin, rectangular area, e.g. 33 mm×2.0 mm. In this embodiment, the distance between a light sensitive element and the adjacent power slab201varies by a maximum of 4 mm, although the light sensitive elements can be positioned at any place in a 66 mm2area. As a result, the variation in voltage drop between power supply lines can be largely reduced.

The non-beam area52may further include an additional interface area57to accommodate further circuitry, for example clock and/or control circuits. The power slabs201may also be arranged to provide sufficient power to the additional interface area57to power these additional circuits.

The beam area51comprises the beamlet deflectors30. The beamlet deflectors30are preferably electrostatic deflectors with a first electrode32and a second electrode34.FIG. 4shows an arrangement of individual beamlet deflectors30. The deflectors30may comprise at least one concave electrode32or34. Suitably, as in the embodiment shown, both electrodes32,34have a concave shape. Apertures35extend through the beamlet array substrate in the beam area51between the electrodes32,34. The concave shape results in the electrodes32,34having a shape conformed to the cylindrical apertures35. This cylindrical aperture shape is in itself suitable for preventing the introduction of certain optical aberrations, such as astigmatism. By carefully choosing the layout and deflection direction, the deflection of the beamlets can be spread out in all directions, preventing undesirable buildup of charge in specific locations of the lithography system.

FIG. 5shows a simplified schematic view of one embodiment of a circuit for control of the beamlet deflectors30. The circuit shown comprises a light sensitive element40, a demultiplexer41, a driver circuit (e.g. an operational amplifier)351, a first electrode32, and a second electrode34. A demultiplexer41may control plural deflectors30. In the embodiment shown, the light sensitive element40is embodied in an optical front end circuit. The circuits are supplied by three power supply terminals202,203,205, and have a common power supply terminal204. The power supply terminals may also be referred to as voltage sources and the common power supply terminal as power supply common. However, electrically such common power supply terminal204may not be considered a single electrical node from an electrical point-of-view, because of significant parasitic impedances of the power wires. For example, in one embodiment the power supply terminal202supplies 3.3 VDC, power supply terminal203supplies 2.2 VDC, and power supply terminal205supplies 1.0 VDC.

The light sensitive element40is served by power supply terminals203and205and is positioned in the non-beam area52. In one embodiment, an optical signal, which carries multiplexed pattern data for control of a group of beamlet deflectors, is directed onto a light sensitive element40. The light sensitive element40converts the optical signal into an electrical signal, and sends the electrical signal to a demultiplexer41, which is served by power supply terminal205. The demultiplexer41demultiplexers the electrical signal to derive separate control signals for control of each individual beamlet deflector30in the group.

If a specific beamlet123is to be deflected, an energizing signal is transmitted to a driving circuit351, which is located in the beam area51close to the relevant first electrode32. The driving circuit351, which is served by power supply terminal202, amplifies the signal and provides the required voltage difference between first electrode32and second electrode34to deflect the incident electron beam123. On the other hand, if a specific beamlet123is not to be deflected, the corresponding first electrode32will not be energized. In this case the incident electron beam123passes through the beamlet deflector30without being deflected.

The light sensitive element40, the demultiplexer41, the driving circuit351and the second electrode34are all connected to a power supply common204which carries the return current to the power supply.

FIG. 6ashows a simplified view of an arrangement of the beamlet blanker array106and multiple power slabs201. Each power slab201is placed perpendicular to the surface of the beamlet blanker array106in a non-beam area52between adjacent beam areas51. Each power slab201has connections to the circuits on the beamlet blanker array106along substantially all the length the power slab which runs adjacent to the beam area51where the beamlet deflectors are located. Each power slab201also has connections to the power supply300via a connector301, the connections made along substantially all the length of the side of the power slab facing the power supply300.

FIG. 6bshows a simplified view of an arrangement of the beamlet blanker array106showing a single power slab201located next to one or more optical fiber bundles208. In this embodiment the power slab201is between two optical fiber bundles208aand208ball connected to the beamlet blanker array between beam areas51aand51b. The power slab201serves half of the beamlet deflectors in both beam areas51aand51bon each side of the power slab, and the optical fiber bundle208aand208bserve half of the beamlet deflectors in beam areas51aand51brespectively.

FIG. 7ashows a more detailed perspective view of a connection between a power slab201and beamlet blanker array106. Each power slab201comprises one or more thin conductive plates arranged in parallel. The embodiment shown comprises four power plates202to205. Each power plate may be connected to the power supply300for supply of a different voltage to the beamlet blanker array. For example, in one embodiment power plates202to205may serve as power supply terminal202(e.g. 3.3 VDC), power supply terminal203(e.g. 2.2 VDC), power supply common204, and power supply terminal205(e.g. 1 VDC), respectively. The material of these power plates is preferably a good conductor and suitable for making a thin plate of uniform dimensions, such as copper. Three electrical insulation layers are sandwiched between the four power plates202to205in order to maintain a very thin structure of the power slab201. The two outer faces of the power plate202and205may also be covered by insulation layers.

In one embodiment, the power plates202to205are in the form of rectangular plates. The plates202to205of each power slab201preferably have approximately the same length and height, while the thickness of each plate may vary. Each plate preferably has a uniform thickness and uniform resistivity over its extent. In a more specific embodiment, the height hslabof each power plate is approximately 28 mm; the length is slightly greater (including allowance for connection to the power supply connectors301); the distance between two adjacent plates is approximately 5 μm; the thickness of an electrical insulation layer sandwiched between the power plates202to205is approximately 10 μm (i.e. the distance between two adjacent plates); the thickness of an outer electrical insulation layer may be thicker or thinner, for example, 8 μm; the thickness of power plates202,203and205is approximately 4 μm and the thickness of power plate204is approximately 15 μm. The sum of the thicknesses, the distances of the power plates202to205(i.e. the thickness of the power slab201) and one outer insulation layer on the power plate202, is about 60 μm.

As the power plate204receives all electrical current flowing in the return circuit to the power supply, the current flowing through it is more than the current flowing in each of the other plates (and is preferably equal to the combined current flowing through all the other plates of the power slab). So it is preferable that power plate204has a sufficiently larger thickness to reduce its resistivity to result in approximately equal thermal expansion under expected operating conditions as the other plates of the power slab. More generally, where different plates of the power slab carry different currents in operation, the relative thicknesses of the plates is preferably arranged so that the expected thermal expansion of the plates, due to the flow of current through the plates, is approximately equal.

It should be noted that, for the power plates202to205, the relative scale of the length, height, thickness and distances is more important than the absolute scale. The length, height, thickness and distances may vary together to be smaller or larger. The power plates202to205are preferably manufactured to have the same, relative to each other, resistivity at every position. Because of the shape of the power plates202to205and their uniform resistivity, electrical current flows uniformly in the plates in operation.

As a general rule in a closed conductive circuit, the overall current flowing from the power supply equals the current flowing in the return circuit. Defining the current flowing in the return circuit as negative for convenience, the sum of the current flowing through the power plates202to205is preferably approximately zero.

Moreover, as the current flows uniformly on the plates202to205due to their uniform resistivity, and as the power plates202to205have the same area (i.e. each of them has the same length and has the same height), the sum of the line current density J (i.e. the current flowing through a unit length) on the power plates202to205is also zero, that is,
J202+J203+J204+J205=0.

It should be recalled that the magnetic field generated by an infinite current sheet (e.g. a conductive plate of infinite size through which the current uniformly flows) is of the form:

In other words, the magnetic field generated by an infinite current sheet is proportional to the current density, and does not vary with distance from the current sheet. In the present invention, the power plates202to205are sufficiently large and thin, i.e. the order of length and height of the plates is much higher than thickness, the plates are sufficiently uniform in thickness, and the plates are placed sufficiently close to each other, that the case of infinite current sheets turns out to be a good approximation. Combining the two equations above, a desirable result can be obtained. That is, in the area outside the space between the power plates202to205, such as in the beam area51, the magnetic field effectively vanishes in the first order approximation:

As a result, a very good cancellation of the magnetic fields generated by the plates of each power slab can be established.

FIG. 7bshows an embodiment of the connection between the power plates202to205of a power slab201and a non-beam area52. In the embodiment shown here, the beamlet blanker array106is comprised of multiple chips50, each chip encompassing a beam area51and a non-beam area52on each side surrounding the beam area, the non-beam area divided into an optical interface area143and a power interface area145. The circuits in the non-beam area are connected to the power plates202to205through a number of conductive bumps207in the power interface area145. Each power plate may be connected separately to the chip50through a separate set of bumps207. The bumps207make an electrical connection between conductive lines on the surface of the chip50to one of the plates of the power slab201. The bumps207may be e.g. solder bumps, for making secure and low resistance connections. Other types of connection other than bumps, such as flexible interconnects, may also be used.

A series of bumps207or solder joints preferably extends along the length of the elongated non-beam area52, making electrical connections along substantially the whole length of the power slab201overlapping with the optical interface area143, to the circuits located along the length of the optical interface area143. Multiple sets of bumps may be used, each set of bumps connecting to a separate plate of the power slab201. In this embodiment, pits are formed in the surface of the power slab201at locations corresponding to the locations of the bumps207to enable the bumps to penetrate through the layers of the power slab to make electrical contact with a desired power plate. For example, inFIG. 7ba first bump207aof a first set of bumps is shown connected to conductive plate205, while a second bump207bof a second set of bumps sits in a corresponding pit to connect to conductive plate204. Only two sets with bumps are shown inFIG. 7bfor simplicity, but it will be understood that four sets of bumps may be used make separate connections to each of the four plates shown in this embodiment.

In the embodiment shown inFIG. 7a, the power slab is formed with a bend of substantially 90 degrees along its length, to form a first portion with its face facing parallel to the surface of the power interface area145and connecting with the bumps207, and a second portion with its face extending substantially perpendicular to the surface of the chip50. A filling material211may be placed in the gap between the first portion of the power slab and the surface of the power interface area145of chip50. This may be an adhesive material to strengthen the bond between the power slab and the chip. A rigid bending profile210may be disposed on the surface facing away from the chip of the first portion of the power slab where the connections to the chip are made. The power slab may be affixed to the bending profile, e.g. using an adhesive, to stiffen the assembly and maintain the 90 degree bend in the slab. To make this structure, the power slab201may be manufactured as a flat structure of parallel plates, the plates are connected in the first portion of the power slab to the chip50via the bumps207, the bending profile210is placed on the first portion of the power slab facing away from the chip50, the power slab bent around the bending profile by 90 degrees, and the underfill placed in the gap between the first portion of the power slab and the chip.

FIG. 7cshows a detailed perspective view of another embodiment of a power slab201. In this embodiment, a single power slab201is formed from two separate sets of power plates201to205each with a first portion as described above for connection to the chip, to provide power to two separate adjacent beam areas51. Two adjoining chips50a,50bare shown, with adjoining non-beam areas52a,52beach connected to a respective first portion of the power slab201. This embodiment may comprise two separate copies of the embodiment shown inFIG. 7b, each being constructed separately and combined by gluing the second portions of each power slab to each other.

FIG. 8shows a simplified schematic diagram of a control circuit for the beamlet deflectors, showing the isolation between the electrical circuits in the non-beam areas52L,52R on each side of a beam area51. As seen a beam area51is served by the both adjacent non-beam areas52L and52R. In the embodiment shown, the beam area51is divided into two at least to some extent isolated halves. For the power supply terminals202L,203L and205L, which provide power to the circuits in the non-beam area52L from a power slab201L connected to the non-beam area52L, the power supply common204which forms a return circuit to the same power slab201L. On the other hand, for the power supply terminals202R,203R and205R, which provide power to the circuits in the non-beam area52R from a power slab201R connected to the non-beam area52R, the power supply common204also forms a return circuit to the same power slab201R. Thus, the beamlet deflectors in a beam area51are controlled by driving circuits located in the non-beam areas52L,52R on both sides of the beam area, where the driving circuits in one non-beam area are at least to some extent electrically isolated from the driving circuits in the other non-beam area (all power supplies202,203,205except for the power supply common204). This isolation seeks to prevent current flow, for example, from power slab201L, to light sensitive elements40L and demultiplexers40L in the non-beam area52L, through the beam area51, to the power supply common204to the adjacent power slab201R. The circuit arrangement seeks to prevent current flow from one power slab to another power slab, as this may unbalance the current flows through a power slab so that the return current is not equal to the forward current in the power slab and the cancellation of the magnetic fields generated by the currents in the power slab is reduced.

FIG. 9shows the simplified diagram of power modulation in the power unit300(power supply arrangement). Three separate DC power feeds (43.2V, 40V, 44.4V) are provided to DC to DC converters312and linear regulators314to generate the voltage supplies 1V, 2.2V, 3.3V respectively. Suitable DC-DC converters are e.g. Vicor VTM chips. By using three separate voltage feeds instead of a single supply feed, the dissipation in the circuits can be kept as small as possible.

FIG. 10shows a simplified, schematic top view of the power unit300. In this embodiment, six groups311of DC-DC converters312for provided for ten power slabs201for providing power to five beam areas located between each pair of power slabs. In the figure only 6 power slabs201have been drawn for simplicity reasons. The outer slabs201each represent a single power slab201and the inner power slabs201comprises a set of two power slabs which are put side by side. Electrically these power slab couples are connected together thus arriving at 6 groups311, wherein for each group311a set of DC-DC converters312is provided. On the power unit300there is also an output area310where linear regulators314and power supply connectors301are located.

It must be emphasized that the invention resides in the conductive power slabs, which each are built up from a plurality of plates which are to be connected between the non-beam area of the modulation device and the circuitry of the power unit (part of the power supply arrangement). A designer has the option to integrate such plates in the modulation device or in the power supply arrangement. The invention covers both options. Expressed differently, the power supply arrangement and the modulation device constitute a plug-socket type of configuration.

The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention, which is defined in the accompanying claims.