NL2010771A - Lithography apparatus and device manufacturing method. - Google Patents

Description

LITHOGRAPHY APPARATUS AND DEVICE MANUFACTURING METHOD Field

[0001] The present invention relates to a lithography or exposure apparatus and a device manufacturing method using the lithography or exposure apparatus.

Background

[0002] A lithographic or exposure apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. A lithographic or exposure apparatus may be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays and other devices or structures having fine features. In a conventional lithographic or exposure apparatus, a patterning device, which may be referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC, flat panel display, or other device). This pattern may transferred on (part of) the substrate (e.g. silicon wafer or a glass plate), e.g. via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0003] Instead of a circuit pattern, the patterning device may be used to generate other patterns, for example a color filter pattern, or a matrix of dots. Instead of a conventional mask, the patterning device may comprise a patterning array that comprises an array of individually controllable elements that generate the circuit or other applicable pattern. An advantage of such a “maskless” system compared to a conventional mask-based system is that the pattern can be provided and/or changed more quickly and for less cost.

[0004] Thus, a maskless system includes a programmable patterning device (e.g., a spatial light modulator, a contrast device, etc.). The programmable patterning device is programmed (e.g., electronically or optically) to form the desired patterned beam using the array of individually controllable elements. Types of programmable patterning devices include micro-mirror arrays, liquid crystal display (LCD) arrays, grating light valve arrays, arrays of self-emissive contrast devices, a shutter element/matrix and the like. A programmable patterning device could also be formed from an electro-optical deflector, configured for example to move spots of radiation projected onto a target (e.g., a substrate) or to intermittently direct a radiation beam away from the target, for example to a radiation beam absorber. In either such arrangement, the radiation beam may be continuous.

Summary

[0005] In a maskless lithographic or exposure apparatus using arrays of self-emissive contrast devices a large optical reduction, e.g. of the order of 1/1,000 to 1/5,000 may need to be effected to direct the separate beams output by the separate self-emissive contrast devices onto a target at a sufficiently small pitch. An optical system that effects such a large reduction involves highly stringent tolerances to provide desired positioning accuracy on the target and may therefore be difficult to manufacture. An approach to reducing the amount of demagnification is to position the self-emissive contrast devices closer together. However, the closeness with which the devices can be positioned is limited by the physical dimensions of the devices themselves as well as associated cooling and mounting structures, especially if the devices are to be individually replaceable.

[0006] It has been proposed to use optical fibers to conduct radiation from spaced apart self-emissive contrast devices with the output ends of the fibers being more closely spaced than the devices. However, optical fibers may not have a sufficient lifetime under the intense radiation of optical lithography. Another approach that has been proposed is to use a stepped mirror. However, such an arrangement involves a very small numerical aperture at the source to provide the desired numerical aperture at the target.

[0007] It is desirable to address at least one of the problems mentioned above and/or one or more other problems in the art. For example, it is desirable to provide a lithographic or exposure apparatus in which radiation beams emitted from an array of sources are directed onto a target with a reduced pitch. For example, it is desirable to provide an optical arrangement to direct radiation from a plurality of spaced apart sources to an array of target points having a reduced pitch that is easier to manufacture and/or has improved lifetime.

[0008] According to an embodiment, there is provided an exposure apparatus comprising: a plurality of source devices configured to produce a plurality of radiation beams to apply individually controllable doses to a target, the plurality of source devices arranged such that the radiation beams are not parallel to one another; and a projection system configured to project each of the radiation beams onto a respective location on the target, the projection system comprising a redirecting element arranged to receive the radiation beams and redirect them onto substantially parallel paths.

[0009] According to an embodiment, there is provided a device manufacturing method, comprising: using a plurality of radiation beams to apply individually controllable doses to a target; and projecting each of the radiation beams onto a respective location on the target, wherein projecting comprises redirecting the plurality of non-parallel radiation beams into respective mutually parallel paths.

Brief Description of the Drawings

[0010] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0011] Figure 1 depicts a part of a lithographic or exposure apparatus according to an embodiment of the invention;

[0012] Figure 2 depicts a top view of a part of the apparatus of Figure 1 according to an embodiment of the invention;

[0013] Figure 3 depicts a highly schematic, perspective view of a part of a lithographic or exposure apparatus according to an embodiment of the invention;

[0014] Figure 4 depicts a schematic top view of projections by the apparatus according to Figure 3 onto a substrate according to an embodiment of the invention;

[0015] Figure 5 depicts in cross-section, a part of an embodiment of the invention;

[0016] Figure 6 depicts an optical arrangement according to an embodiment of the present invention;

[0017] Figure 7 depicts an optical arrangement according to an embodiment of the present invention; and

[0018] Figure 8 depicts an optical arrangement according to an embodiment of the present invention.

Detailed Description

[0019] The present invention relates to a lithographic apparatus that may include a programmable patterning device that may, for example, be comprised of an array of self-emissive contrast devices. Further information regarding such lithographic apparatus may be found in WO 2010/032224 A2, which is hereby incorporated by reference. It should be appreciated, however, that the present invention may be used with any form of programmable patterning device including, for example, those discussed above.

[0020] Figure 1 schematically depicts a schematic cross-sectional side view of a part of a lithographic or exposure apparatus. In this embodiment, the apparatus has individually controllable elements substantially stationary in the X-Y plane as discussed further below although it need not be the case. The apparatus 1 comprises a substrate table 2 to hold a substrate, and a positioning device 3 to move the substrate table 2 in up to 6 degrees of freedom. The substrate may be a resist-coated substrate. In an embodiment, the substrate is a wafer. In an embodiment, the substrate is a polygonal (e.g. rectangular) substrate. In an embodiment, the substrate is a glass plate. In an embodiment, the substrate is a plastic substrate. In an embodiment, the substrate is a foil. In an embodiment, the apparatus is suitable for roll-to-roll manufacturing.

[0021] The apparatus 1 further comprises a plurality of individually controllable self-emissive contrast devices 4 configured to emit a plurality of beams. In an embodiment, the self-emissive contrast device 4 is a radiation emitting diode, such as a light emitting diode (LED), an organic LED (OLED), a polymer LED (PLED), or a laser diode (e.g., a solid state laser diode). In an embodiment, each of the individually controllable elements 4 is a blue-violet laser diode (e.g., Sanyo model no. DL-3146-151). Such diodes may be supplied by companies such as Sanyo, Nichia, Osram, and Nitride. In an embodiment, the diode emits UV radiation, e.g., having a wavelength of about 365 nm or about 405 nm. In an embodiment, the diode can provide an output power selected from the range of 0.5 - 200 mW. In an embodiment, the size of laser diode (naked die) is selected from the range of 100 - 800 micrometers.

In an embodiment, the laser diode has an emission area selected from the range of 0.5 - 5 micrometers2. In an embodiment, the laser diode has a divergence angle selected from the range of 5 - 44 degrees. In an embodiment, the diodes have a configuration (e.g., emission area, divergence angle, output power, etc.) to provide a total brightness more than or equal to about 6.4 x 108 W/(m2.sr).

[0022] The self-emissive contrast devices 4 are arranged on a frame 5 and may extend along the Y-direction and/or the X direction. While one frame 5 is shown, the apparatus may have a plurality of frames 5 as shown in Figure 2. Further arranged on the frame 5 is lens 12. Frame 5 and thus self-emissive contrast device 4 and lens 12 are substantially stationary in the X-Y plane. Frame 5, self-emissive contrast device 4 and lens 12 may be moved in the Z-direction by actuator 7. Alternatively or additionally, lens 12 may be moved in the Z-direction by an actuator related to this particular lens. Optionally, each lens 12 may be provided with an actuator.

[0023] The self-emissive contrast device 4 may be configured to emit a beam and the projection system 12,14 and 18 may be configured to project the beam onto a target portion of the substrate. The self-emissive contrast device 4 and the projection system form an optical column. The apparatus 1 may comprise an actuator (e.g. motor 11) to move the optical column or a part thereof with respect to the substrate. Frame 8 with arranged thereon field lens 14 and imaging lens 18 may be rotatable with the actuator. A combination of field lens 14 and imaging lens 18 forms movable optics 9. In use, the frame 8 rotates about its own axis 10, for example, in the directions shown by the arrows in FIG. 2. The frame 8 is rotated about the axis 10 using an actuator e.g. motor 11. Further, the frame 8 may be moved in a Z direction by motor 7 so that the movable optics 9 may be displaced relative to the substrate table 2.

[0024] An aperture structure 13 having an aperture therein may be located above lens 12 between the lens 12 and the self-emissive contrast device 4. The aperture structure 13 can limit diffraction effects of the lens 12, the associated self-emissive contrast device 4, and/or of an adjacent lens 12 / self-emissive contrast device 4.

[0025] The depicted apparatus may be used by rotating the frame 8 and simultaneously moving the substrate on the substrate table 2 underneath the optical column. The self-emissive contrast device 4 can emit a beam through the lenses 12, 14, and 18 when the lenses are substantially aligned with each other. By moving the lenses 14 and 18, the image of the beam on the substrate is scanned over a portion of the substrate. By simultaneously moving the substrate on the substrate table 2 underneath the optical column, the portion of the substrate which is subjected to an image of the self-emissive contrast device 4 is also moving. By switching the self-emissive contrast device 4 “on” and “off” (e.g., having no output or output below a threshold when it is “off” and having an output above a threshold when it is “on”) at high speed under control of a controller, controlling the rotation of the optical column or part thereof, controlling the intensity of the self-emissive contrast device 4, and controlling the speed of the substrate, a desired pattern can be imaged in the resist layer on the substrate.

[0026] Figure 2 depicts a schematic top view of the apparatus of Figure 1 having self-emissive contrast devices 4. Like the apparatus 1 shown in Figure 1, the apparatus 1 comprises a substrate table 2 to hold a substrate 17, a positioning device 3 to move the substrate table 2 in up to 6 degrees of freedom, an alignment/level sensor 19 to determine alignment between the self-emissive contrast device 4 and the substrate 17, and to determine whether the substrate 17 is at level with respect to the projection of the self emissive contrast device 4. As depicted the substrate 17 has a rectangular shape, however also or alternatively round substrates may be processed.

[0027] The self-emissive contrast device 4 is arranged on a frame 15. The self-emissive contrast device 4 may be a radiation emitting diode, e.g., a laser diode, for instance a blue-violet laser diode. As shown in Figure 2, the self-emissive contrast devices 4 may be arranged into an array 21 extending in the X-Y plane.

[0028] The array 21 may be an elongate line. In an embodiment, the array 21 may be a single dimensional array of self-emissive contrast devices 4. In an embodiment, the array 21 may be a two dimensional array of self-emissive contrast device 4.

[0029] A rotating frame 8 may be provided which may be rotating in a direction depicted by the arrow. The rotating frame may be provided with lenses 14, 18 (show in Figure 1) to provide an image of each of the self-emissive contrast devices 4. The apparatus may be provided with an actuator to rotate the optical column comprising the frame 8 and the lenses 14,18 with respect to the substrate.

[0030] Figure 3 depicts a highly schematic, perspective view of the rotating frame 8 provided with lenses 14, 18 at its perimeter. A plurality of beams, in this example 10 beams, are incident onto one of the lenses and projected onto a target portion of the substrate 17 held by the substrate table 2. In an embodiment, the plurality of beams are arranged in a straight line. The rotatable frame is rotatable about axis 10 by means of an actuator (not shown). As a result of the rotation of the rotatable frame 8, the beams will be incident on successive lenses 14, 18 (field lens 14 and imaging lens 18) and will, incident on each successive lens, be deflected thereby so as to travel along a part of the surface of the substrate 17, as will be explained in more detail with reference to Fig. 4. In an embodiment, each beam is generated by a respective source, i.e. a self-emissive contrast device, e.g. a laser diode (not shown in Figure 3). In the arrangement depicted in Figure 3, the beams are deflected and brought together by a segmented mirror 30 in order to reduce a distance between the beams, to thereby enable a larger number of beams to be projected through the same lens and to achieve resolution requirements to be discussed below.

[0031] As the rotatable frame rotates, the beams are incident on successive lenses and, each time a lens is irradiated by the beams, the places where the beam is incident on a surface of the lens, moves. Since the beams are projected on the substrate differently (with e.g. a different deflection) depending on the place of incidence of the beams on the lens, the beams (when reaching the substrate) will make a scanning movement with each passage of a following lens. This principle is further explained with reference to Figure 4. Figure 4 depicts a highly schematic top view of a part of the rotatable frame 8. A first set of beams is denoted by B1, a second set of beams is denoted by B2 and a third set of beams is denoted by B3. Each set of beams is projected through a respective lens set 14, 18 of the rotatable frame 8. As the rotatable frame 8 rotates, the beams B1 are projected onto the substrate 17 in a scanning movement, thereby scanning area A14. Similarly, beams B2 scan area A24 and beams B3 scan area A34. At the same time of the rotation of the rotatable frame 8 by a corresponding actuator, the substrate 17 and substrate table are moved in the direction D, which may be along the X axis as depicted in Figure 2), thereby being substantially perpendicular to the scanning direction of the beams in the areas A14, A24, A34.

[0032] As a result of the movement in direction D by a second actuator (e.g. a movement of the substrate table by a corresponding substrate table motor), successive scans of the beams when being projected by successive lenses of the rotatable frame 8, are projected so as to substantially abut each other, resulting in substantially abutting areas A11, A12, A13, A14 (areas A11, A12, A13 being previously scanned and A14 being currently scanned as shown in Figure 4) for each successive scan of beams B1, areas A21, A22, A23 and A24 (areas A21, A22, A23 being previously scanned and A24 being currently scanned as shown in Figure 4) for beams B2 and areas A31, A32, A33 and A34 (areas A31, A32, A33 being previously scanned and A34 being currently scanned as shown in Figure 4) for beams B3. Thereby, the areas A1, A2 and A3 of the substrate surface may be covered with a movement of the substrate in the direction D while rotating the rotatable frame 8.

[0033] The projecting of multiple beams through a same lens allows processing of a whole substrate in a shorter timeframe (at a same rotating speed of the rotatable frame 8), since for each passing of a lens, a plurality of beams scan the substrate with each lens, thereby allowing increased displacement in the direction D for successive scans. Viewed differently, for a given processing time, the rotating speed of the rotatable frame may be reduced when multiple beams are projected onto the substrate via a same lens, thereby possibly reducing effects such as deformation of the rotatable frame, wear, vibrations, turbulence, etc. due to high rotating speed. In an embodiment, the plurality of beams are arranged at an angle to the tangent of the rotation of the lenses 14, 18 as shown in Figure 4. In an embodiment, the plurality of beams are arranged such that each beam overlaps or abuts a scanning path of an adjacent beam.

[0034] A further effect of the aspect that multiple beams are projected at a time by the same lens, may be found in relaxation of tolerances. Due to tolerances of the lenses (positioning, optical projection, etc), positions of successive areas A11, A12, A13, A14 (and/or of areas A21, A22, A23 and A24 and/or of areas A31, A32, A33 and A34) may show some degree of positioning inaccuracy in respect of each other. Therefore, some degree of overlap between successive areas A11, A12, A13, A14 may be required. In case of for example 10% of one beam as overlap, a processing speed would thereby be reduced by a same factor of 10% in case of a single beam at a time through a same lens. In a situation where there are 5 or more beams projected through a same lens at a time, the same overlap of 10% (similarly referring to one beam example above) would be provided for every 5 or more projected lines, hence reducing a total overlap by a factor of approximately 5 or more to 2% or less, thereby having a significantly lower effect on overall processing speed. Similarly, projecting at least 10 beams may reduce a total overlap by approximately a factor of 10. Thus, effects of tolerances on processing time of a substrate may be reduced by the feature that multiple beams are projected at a time by the same lens. In addition or alternatively, more overlap (hence a larger tolerance band) may be allowed, as the effects thereof on processing are low given that multiple beams are projected at a time by the same lens.

[0035] Alternatively or in addition to projecting multiple beams via a same lens at a time, interlacing techniques could be used, which however may require a comparably more stringent matching between the lenses. Thus, the at least two beams projected onto the substrate at a time via the same one of the lenses have a mutual spacing, and the apparatus may be arranged to operate the second actuator so as to move the substrate with respect to the optical column to have a following projection of the beam to be projected in the spacing.

[0036] In order to reduce a distance between successive beams in a group in the direction D (thereby e.g. achieving a higher resolution in the direction D), the beams may be arranged diagonally in respect of each other, in respect of the direction D. The spacing may be further reduced by providing a segmented mirror 30 in the optical path, each segment to reflect a respective one of the beams, the segments being arranged so as to reduce a spacing between the beams as reflected by the mirrors in respect of a spacing between the beams as incident on the mirrors. Such effect may also be achieved by a plurality of optical fibers, each of the beams being incident on a respective one of the fibers, the fibers being arranged so as to reduce along an optical path a spacing between the beams downstream of the optical fibers in respect of a spacing between the beams upstream of the optical fibers.

[0037] Further, such effect may be achieved using an integrated optical waveguide circuit having a plurality of inputs, each for receiving a respective one of the beams. The integrated optical waveguide circuit is arranged so as to reduce along an optical path a spacing between the beams downstream of the integrated optical waveguide circuit in respect of a spacing between the beams upstream of the integrated optical waveguide circuit.

[0038] A system may be provided for controlling the focus of an image projected onto a substrate. The arrangement may be provided to adjust the focus of the image projected by part or all of an optical column in an arrangement as discussed above.

[0039] In an embodiment the projection system projects the at least one radiation beam onto a substrate formed from a layer of material above the substrate 17 on which a device is to be formed so as to cause local deposition of droplets of the material (e.g. metal) by a laser induced material transfer.

[0040] Referring to FIG. 5, the physical mechanism of laser induced material transfer is depicted. In an embodiment, a radiation beam 200 is focused through a substantially transparent material 202 (e.g., glass) at an intensity below the plasma breakdown of the material 202. Surface heat absorption occurs on a substrate formed from a donor material layer 204 (e.g., a metal film) overlying the material 202. The heat absorption causes melting of the donor material 204. Further, the heating causes an induced pressure gradient in a forward direction leading to forward acceleration of a donor material droplet 206 from the donor material layer 204 and thus from the donor structure (e.g., plate) 208. Thus, the donor material droplet 206 is released from the donor material layer 204 and is moved (with or without the aid of gravity) toward and onto the substrate 17 on which a device is to be formed. By pointing the beam 200 on the appropriate position on the donor plate 208, a donor material pattern can be deposited on the substrate 17. In an embodiment, the beam is focused on the donor material layer 204.

[0041] In an embodiment, one or more short pulses are used to cause the transfer of the donor material. In an embodiment, the pulses may be a few picoseconds or femto-seconds long to obtain quasi one dimensional forward heat and mass transfer of molten material. Such short pulses facilitate little to no lateral heat flow in the material layer 204 and thus little or no thermal load on the donor structure 208. The short pulses enable rapid melting and forward acceleration of the material (e.g., vaporized material, such as metal, would lose its forward directionality leading to a splattering deposition). The short pulses enable heating of the material to just above the heating temperature but below the vaporization temperature. For example, for aluminum, a temperature of about 900 to 1000 degrees Celsius is desirable.

[0042] In an embodiment, through the use of a laser pulse, an amount of material (e.g., metal) is transferred from the donor structure 208 to the substrate 17 in the form of 100-1000 nm droplets. In an embodiment, the donor material comprises or consists essentially of a metal. In an embodiment, the metal is aluminum. In an embodiment, the material layer 204 is in the form a film. In an embodiment, the film is attached to another body or layer. As discussed above, the body or layer may be a glass.

[0043] Figure 6 depicts an optical arrangement of a source module of the lithographic or exposure apparatus. A plurality of source devices 4, acting as self-emissive contrast devices, are arranged in an array. In an embodiment, the array is a one-dimensional array, i.e. a line, on the surface of a notional sphere A. For example, the source devices 4 are arranged on a circular arc.

In an embodiment, the source devices are arranged in a two-dimensional array on the surface of the notional sphere. In an embodiment, the two-dimensional array is a staggered array. In an embodiment there are 10 or more source devices, desirably 20 or more, or desirably 30 or more. Any of the radiation emitting devices mentioned above can be used as the source devices.

[0044] Desirably, the source devices 4 are as close together as possible, allowing for any necessary mounting and/or cooling arrangements, etc. In an embodiment, the source devices 4 are mounted individually so that they can be separately removed from the apparatus for servicing or replacement.

[0045] A collimating lens 121 is provided for each source device 4 to collect the radiation emitted thereby and direct it into a collimated beam 41. Collimated beams 41 are directed towards the center of the notional sphere A on which the source devices 4 are positioned. An array of lenses 122 receives the collimated beams 41 and converges the radiation into converging beams 42 directed towards the center of the notional sphere A. A negative lens group 123 comprising one or more lenses and acting as a redirecting element, receives the converging beams 42 and re-directs them into a set of substantially parallel collimated beams 43. The collimated beams 43 have reduced beam widths (e.g., diameters) and a reduced pitch (i.e. spacing between beams) compared to the collimated beams 41 formed by collimating lenses 121.

[0046] In an embodiment, the lenses 122 contact one another and are positioned at a distance from the collimating lenses 121 at which the collimated beams 41 begin to overlap. The lenses 122 form a closely packed array. The power of lenses 122 is selected such that the converging beams 42 substantially do not overlap one another when incident on the negative lens group 123. Negative lens group 123 is located such that its focal point fp is at the center of the notional sphere A on which the source devices 4 are arranged. The focal length Fn of the negative lens group 123 is given by the following expression:

Fn = d-R/

/ P

where dis the desired pitch of the beams after the negative lens. R is the radius of the notional sphere A on which the source devices 4 are arranged and p is the pitch of the source devices 4. In an embodiment, R = 300 mm, p = 10 mm and d= 0.3 mm giving a negative focal length of 9 mm. In an embodiment, the pitch of the beams after the negative lens 123 is less than about 1 mm. In an embodiment, the pitch of the radiation source devices 4 is greater than about 5 mm.

[0047] Figure 7 depicts a further embodiment in which the negative lens group 123 is replaced by a positive lens group 124 located after the focal point fp. The positive lens group 124 acts as the redirecting element. This arrangement provides an equivalent output as the arrangement of Figure 6 but results in a larger construction.

[0048] A further embodiment is shown in Figure 8. This embodiment is essentially the same as that of Figure 6 save as described below but is also shown in the context of the complete optical system of the apparatus. In the embodiment of Figure 8, the substantially parallel beams output from negative lens 123 (the redirecting element) are received by a first optical system comprising first, second and third lens groups 125, 126 and 127 which de-magnify the beams, e.g. by a factor of 1 /10, and adjust the focus. These lens groups correspond to lens 12 shown in Figure 1. Substantially parallel beams having a reduced pitch, compared to the beams output from redirecting element 123, are output by first lens system 125, 126, 127. These substantially parallel beams have, in an embodiment, a pitch of about 0.03 mm. A second optical system comprising lens groups 14 and 18 is mounted on rotor 8 and effects a further reduction, e.g. by a factor of about 15, so that the pitch of the spots projected onto the target is about 2 pm for example. The total reduction factor of the projection optical system 125, 126, 127, 14 and 18, e.g. about 1/150, means that the system is easier to manufacture than a system which has a reduction of about 1/1,000 - 1/5,000.

[0049] In the embodiment of Figure 8, an opaque member or plate 131 having a pinhole corresponding to each of the source devices 4 is provided in the collimated beams 41. The pinholes in plate 131 can be positioned with a high degree of accuracy and serve to eliminate uncertainty in the beam position that might be caused by uncertainty in the positions of source devices 4. In an embodiment, a further pinhole array is provided in a pupil plane PP of the first optical system to correct angular uncertainty in the beams deriving from positional uncertainty of the source devices 4.

[0050] In the above, beam widths or diameters referred to are full width half maximum widths. Beam pitches are center-to-center distances.

[0051] In accordance with a device manufacturing method, a device, such as a display, integrated circuit or any other item may be manufactured from the substrate on which the pattern has been projected.

[0052] Although specific reference may be made in this text to the use of lithographic or exposure apparatus in the manufacture of ICs, it should be understood that the apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer 1C, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0053] The term “lens”, where the context allows, may refer to any one of various types of optical components, including refractive, diffractive, reflective, magnetic, electromagnetic and electrostatic optical components or combinations thereof.

[0054] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the embodiments of the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein. Further, the machine-readable instruction may be embodied in two or more computer programs.

The two or more computer programs may be stored on one or more different memories and/or data storage media.

The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the clauses set out below. Other aspects of the invention are set out as in the following numbered clauses: 1. An exposure apparatus comprising: a plurality of source devices configured to produce a plurality of radiation beams to apply individually controllable doses to a target, the plurality of source devices arranged such that the radiation beams are not parallel to one another; and a projection system configured to project each of the radiation beams onto a respective location on the target, the projection system comprising a redirecting element arranged to receive the radiation beams and redirect them onto substantially parallel paths.

2. The apparatus according to clause 1, wherein the redirecting element is a refractive lens group.

3. The apparatus according to clause 2, wherein refractive lens group consists of a single refractive lens element.

4. The apparatus according to any of clauses 1-3, wherein the redirecting element has a negative power.

5. The apparatus according to any of clauses 1-3, wherein the redirecting element has a positive power.

6. The apparatus according to any of the preceding clauses, wherein each of the source devices comprises a collimating lens.

7. The apparatus according to any of the preceding clauses, wherein the source devices are arranged such that the radiation beams produced are directed towards a common point.

8. The apparatus according to any of the preceding clauses, wherein the projection system comprises a plurality of lenses, corresponding in number to the source devices, arranged to converge the radiation beams.

9. The apparatus according to clause 8, wherein the plurality of lenses are in a closely packed array.

10. The apparatus according to any of the preceding clauses, wherein the redirecting element is arranged to collimate the redirected radiation beams.

11. The apparatus according to any of the preceding clauses, further comprising an opaque member provided in the path of the radiation beams, the opaque member defining a pin hole corresponding to each of the source devices.

12. The apparatus according to clause 11, wherein the opaque member is positioned between the source devices and the redirecting element.

13. The apparatus according to clause 11 or clause 12, wherein the opaque member is provided in a pupil plane of the projection system.

14. The apparatus according to any of the preceding clauses, wherein the target is a layer of donor material spaced apart from a substrate on which a device is to be formed.

15. The apparatus according to any of the preceding clauses, wherein the projection system comprises a stationary part and a moving part.

Claims (1)

A lithography device comprising: an illumination device adapted to provide a radiation beam; a carrier constructed to support a patterning device, the patterning device being capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam; a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.