NL2009591A - Lithographic apparatus and device manufacturing method. - Google Patents

Description

LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD

FIELD

[0001] The present invention relates to an exposure apparatus, a lithographic apparatus, and a method for manufacturing a device.

BACKGROUND

[0002] A lithographic apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. A lithographic 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 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 1C, 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. In a similar regard, an exposure apparatus is a machine that use a radiation beam in forming a desired pattern on or in a substrate (or a part thereof).

[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 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 the substrate or to intermittently direct a radiation beam away from the substrate, for example to a radiation beam absorber. In either such arrangement, the radiation beam may be continuous.

SUMMARY

[0005] In a lithographic or exposure process, a plurality of radiation beams may be created, patterned and projected onto a substrate. In one example, an array or arrays of self-emissive contrast devices may be used in order to generate the radiation beams.

[0006] Generally the size of the substrate, in plan, will be greater than that of a projection system module used to project the plurality of radiation beams onto the substrate. This can be undesirable in that when (part of) the substrate is not under the projection system module, contaminant particles, such as dust particles, may land on the top surface of the substrate. This can lead to pattern forming (e.g., imaging) errors which is clearly undesirable.

[0007] In order to mitigate against the risk of contaminant particles landing on (part of) the substrate not under the projection system module, one or more gas shower modules may be positioned adjacent the projection system module to provide a flow of filtered gas onto a part of the substrate not under the projection system module.

[0008] In an embodiment, the projection system module is mechanically isolated from the gas shower module. Therefore, there is no direct connection between the projection system module and the gas shower module (e.g., the two modules may be separately connected to a solid ground or the two modules may be connected via a damper or other isolation structure). A gap may be present between the two modules. Contaminant particles may fall and/or be pulled by a flow of gas into the gap between the projection system module and gas shower module and thereby land on the substrate. This is undesirable.

[0009] It is therefore desirable, for example, to provide an apparatus in which one or more measures are taken to reduce the chance of a contaminant particle falling onto a top surface of a substrate, for example, through a gap between the projection system module and gas shower module.

[0010] According to an embodiment of the invention, there is provided an exposure apparatus, comprising: a projection system module, configured to project a radiation beam onto a substrate; a gas shower module, configured to provide a flow of gas onto a top surface of a substrate when uncovered, in plan, by the projection system module; and a sealing gas outlet to provide a sealing flow of gas directed in a direction from the projection system module towards the gas shower module, or vice versa.

[0011] According to an embodiment of the invention, there is provided a device manufacturing method comprising: using a projection system module to project a radiation beam onto a substrate; using a gas shower module to provide a flow of gas onto a top surface of a substrate when uncovered, in plan, by the projection system module; and providing a sealing flow of gas which is directed in a direction from the projection system module towards the gas shower module, or vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] 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:

[0013] Figure 1 depicts a part of a lithographic or exposure apparatus according to an embodiment of the invention;

[0014] Figure 2 depicts a top view of a part of the lithographic or exposure apparatus of Figure 1 according to an embodiment of the invention;

[0015] Figure 3 depicts a highly schematic, perspective view of a part of a lithographic or exposure apparatus according to an embodiment of the invention;

[0016] Figure 4 depicts a schematic top view of projections by the lithographic or exposure apparatus according to Figure 3 onto a substrate according to an embodiment of the invention;

[0017] Figure 5 depicts, in cross-section, a part of an embodiment of the invention;

[0018] Figure 6 illustrates, in cross-section, a part of a lithographic or exposure apparatus;

[0019] Figure 7 illustrates, in plan, a part of a lithographic or exposure apparatus;

[0020] Figure 8 illustrates, in cross-section, a detail of a gap between a projection system module and a gas shower module illustrating a problem addressed by an embodiment of the present invention;

[0021] Figure 9 illustrates, in cross-section, a detail of a lithographic or exposure apparatus according to an embodiment of the invention;

[0022] Figure 10 illustrates, in cross-section, a detail of a lithographic or exposure apparatus according to an embodiment of the invention;

[0023] Figure 11 illustrates, in cross-section, a detail of a lithographic or exposure apparatus according to an embodiment of the invention; and

[0024] Figure 12 illustrates, in cross-section, a detail of a lithographic or exposure apparatus according to an embodiment of the invention.

DETAILED DESCRIPTION

[0025] An embodiment of the present invention relates to an apparatus that may include a programmable patterning device that may, for example, be comprised of an array or arrays of self-emissive contrast devices. Further information regarding such an apparatus may be found in PCT patent application publication no. WO 2010/032224 A2, U.S. patent application publication no. US 2011-0188016, U.S. patent application no.

US 61/473636 and U.S. patent application no. 61/524190 which are hereby incorporated by reference in their entireties. An embodiment of the present invention, however, may be used with any form of programmable patterning device including, for example, those discussed above.

[0026] 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.

[0027] 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 or about 436 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 of more than or equal to about 6.4 x 108 W/(m2.sr).

[0028] 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 in Figure 1, the apparatus may have a plurality of frames 5. Further arranged on the frame 5 are lenses 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.

[0029] 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 combinations of field lenses 14 and imaging lenses 18 form movable optics 9. In use, the frame 8 rotates about its own axis 10, for example, in the directions shown by the arrows in Figure 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.

[0030] 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.

[0031] 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.

[0032] 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 shown in Figure 2 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.

[0033] 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.

[0034] 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 devices 4.

[0035] 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.

[0036] 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 sets of 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 Figure 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.

[0037] As the rotatable frame rotates, the sets of beams are incident on successive lenses and, each time a lens is irradiated by the beams, the places where the beams are incident on a surface of the lens move. 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 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 area’s A14, A24, A34. 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. 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.

[0038] 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.

[0039] 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. The at least two beams projected onto the substrate at a time via the same lens 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Referring to Figure 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.

[0045] 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 femtoseconds 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 melting temperature but below the vaporization temperature. For example, for aluminum, a temperature of about 900 to 1000 degrees Celsius is desirable.

[0046] 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.

[0047] Figure 6 illustrates, in cross-section, a part of a lithographic or exposure apparatus. A projection system module 310 is illustrated which includes all of the components supported by frame 15 illustrated in Figure 1. That is, the projection system module 310 comprises the optical components which are supported on a so called metro frame 15. Another term for the projection system module 310 is an engine metro frame.

[0048] A substrate table 2 is also illustrated in Figure 6. In an embodiment, the substrate table 2 is dynamically isolated from the projection system module 310. In a system such as that of Figure 1 which uses a plurality of projection beams, the substrate W is likely to be quite large. The substrate W may have a footprint, in plan, which is significantly greater than the footprint of the projection system module 310.

Therefore, a part of the substrate W may be uncovered by the projection system module 310, as illustrated in Figures 6 and 7.

[0049] A difficulty with a part of the substrate W positioned on the substrate table 2 not being covered by the projection system module 310 (at least during imaging of certain parts of the substrate) is one of contamination. That is, contaminant particles 340 may fall onto a top surface of the substrate W when it is not covered by the projection system module 310. If contaminant particles 340 fall onto the substrate W, they may interfere with pattern forming (e.g., imaging projection beams) thereby causing defects in the pattern on the substrate W. Therefore, this situation is undesirable and steps are taken to reduce or minimize the chance of contaminant particles landing on the substrate W.

[0050] Figure 6 illustrates how this can be done. First and second gas shower modules 320, 330 may be provided on either side of the projection system module 310 to provide a flow of gas 322, 332 (e.g. a gas shower) onto a top surface of the substrate W which is not covered by the projection system module 310. The flow of gas 322 onto the top surface of the substrate is provided through a series of openings 3222 in a two dimensional array which extends over the area of the substrate W which is present under the first gas shower module 320. The second gas shower module 330 operates in the same way. The first and second gas shower modules 320, 330 are illustrated on the left and right hand side of the projection system module 310 as illustrated in Figure 6. This is because (as illustrated in Figure 7) the substrate W has the same width as the projection system module 310 in the Y-direction but is longer than the projection system module 310 in the X-direction. Therefore, the first and second gas shower modules 320, 330 are positioned before and after the projection system module 310 in the X direction. In an embodiment, the first and second gas shower modules 320, 330 may be a single gas shower module that extends around the projection system module 310.

[0051] Using the first and/or second gas shower modules 320, 330, a gas shower is provided onto the top surface of the substrate (using filtered gas) to help prevent contaminant particles from reaching and/or settling onto the substrate W. The flow of gas 322, 332 may be humidified gas and/or temperature conditioned gas so as to be useful in controlling the temperature of the substrate W. The flow of gas 322, 332 can also be provided onto the substrate table 2. Particles in or on the substrate table 2 will be inhibited from reaching the substrate W.

[0052] The first and second gas shower modules 320, 330 may be the same or similar to those described in U.S. patent no. US 7,522,258 herein by incorporated in its entirety by reference.

[0053] The first and second gas shower modules 320, 330 are dynamically decoupled from the projection system module 310 so as to avoid vibrations entering the projection system module 310 and thereby deleteriously affecting pattern forming (e.g., imaging). This results in a gap 305 being present between the projection system module 310 and the first gas shower module 320 on one side and between the projection system module 310 and the second gas shower module 330 on the other side.

[0054] Contaminant particles may fall through the gap 305 in a contaminant carrying gas flow 302 explained in more detail with reference to Figure 8. An embodiment of the invention addresses this potential source of contaminant particles landing on the substrate.

[0055] The contaminant carrying gas flow 302 on either side of the projection system module 310 may be generated due to the presence of the flows of gas 322, 332 of the gas shower modules 320, 330 and/or due to movement of the substrate table 2 (by creating an underpressure in its wake thereby drawing gas through the gap 305). Other potential drivers for the contaminant carrying gas flow 302 are service actions, opening of covers or doors of the apparatus, exhaust particle extraction points (e.g. underpressure sources), thermal conditioning gas flows (such as those optionally applied to components of the projection system module 310) and thermal differences between components of the apparatus.

[0056] Another and potentially more serious source for the contaminant carrying gas flow 302 is movement of a substrate handler. In an embodiment the first gas shower module 320 is also a substrate handler. The substrate handler is used to unload and load a substrate from a track on which the substrate W is delivered to the apparatus 1. The substrate W is then transferred and placed on (and later unloaded from) the substrate table 2 by the substrate handler. The substrate handler moves in the Z-direction to accomplish these tasks. During scanning of the substrate W the substrate handler is positioned such that outlets 3222 through which the flow of gas 322 leaves the gas shower module 320 are positioned at the same height as the outlets 3222 of the second gas shower module 330. Thus, the handler during scanning is positioned as shown in solid lines on the left hand side of Figure 6. During transport of the substrate W from the track and substrate table 2 the handler 320 may be positioned as shown in dashed lines on the left hand side of Figure 6. Therefore, the first gas shower module 320 may move in the Z direction (the direction to which the optical axis of the apparatus is parallel) as indicated by the arrow in the left hand side of Figure 6. Such vertical movement, particularly during movement from the dashed position to the solid position as shown in Figure 6 (i.e. upwards movement away from the substrate W) can cause an underpressure to be generated under the first gas shower module 320 thereby drawing in a contaminant carrying gas flow 302 (shown in dashed lines) through the gap 305.

[0057] Figure 7 illustrates, in plan, the projection system module 310, first and second gas shower modules 320, 330 and substrate W (shown in cross-hatching).

[0058] The gas showers defined by the flows of gas 322, 332 create an overpressure above the substrate W and a certain outflow velocity on the sides of the covered (by the modules 310, 320, 330) substrate W. These outflow velocities illustrated in Figure 7 by arrows 3221 and 3321 help to prevent particles from entering the space above the substrate W. As illustrated in Figure 7, there is an increase in flow velocity in the gap 305 away from the center towards an edge. There is less resistance to flow at the outer locations. Such a greater flow velocity at the outer locations results in a lower underpressure at those locations and thereby a larger sucking force on gas above the gap 305. Thus, a larger contaminant carrying gas flow 302 can be expected at the sides of the gap 305 (in plan) rather than in the center. When the substrate is not present under a gap 305, the flow below the gap 305 is likely to be more equal along the length of the gap.

[0059] In an embodiment, the substrate W under the projection system module 310 is not necessarily the same substrate W as under the first or second gas shower module 320, 330.

[0060] Figure 8 shows in detail the gap 305 and origin of contaminant particles 340 on a top surface of the substrate W supported on the substrate table 2. The gap 305 shown is the gap between the projection system module 310 and the first gas shower module 320, but the gap 305 on the other side of the projection system module 310 may be treated in the same way. The contaminant carrying gas flow 302 carries contaminant particles 340 through the gap 305. This may even be in the case when the gap 305 is narrowed by use of a projection 307 mounted on the projection system module 310.

[0061] The contaminant carrying gas flow 302 may be generated by some extent due to movement of the substrate table 2 moving under the projection system module 310 leaving an underpressure in its wake.

[0062] In the case that the substrate W is under the gap 305, contaminant particles 340 which find their way through the gap 305, for example carried by contaminant carrying gas flow 302, can end up on the top surface of the substrate W. This can lead to pattern forming (e.g., imaging) errors.

[0063] One solution might be to provide a covering or flexible sealing mechanism between the first gas shower module 320 and projection system module 310. However, such a cover might undesirably transmit disturbance forces between the two modules 310, 320 and will itself be a particle generator, particularly if it needs to move (for example to accommodate movement of the substrate handler). Another option might be a labyrinth seal, at the expense of increased complexity and need for a finer tolerance. Additionally, in such a system, the substrate may be 3 meters wide and with such a long gap it is not a simple matter to design an accurate enough sealing without gaps due to tolerances.

[0064] Figure 9 illustrates an embodiment of the present invention which addresses one or more of the above mentioned or other difficulties. At least one gas sealing outlet 325 is provided in a side wall of the gas shower module 320. The sealing gas outlet 325 extends along the width of the first gas shower module 320, for example all the way along the Y-axis. A gas flow 3255 (shown in dotted lines) is provided out of the sealing gas outlet 325. The sealing flow of gas 3255 is directed towards the projection system module 310. A component of the sealing flow of gas 3255, as shown in a dotted line is directed away from the substrate W (e.g. upwards in the gap 305). In an embodiment the sealing flow of gas 3255 is directly directed with an upward component (e.g. away from the substrate W) by the sealing gas outlet 325. Additionally or alternatively in an embodiment the sealing flow of gas 3255 is indirectly directed with an upward component, for example by hardware opposing the gas exiting the sealing gas outlet 325 which directs the gas upwards. The sealing flow of gas 3255 thereby bends the contaminant carrying gas flow 3021 such that the gas flow is directed away from the gap 305. The contaminant particles 340 are transported in the contaminant carrying gas flow 3021 away from the gap 305 and away from the substrate W. The sealing flow of gas 3255 provides a barrier to contaminant particles 340 in the gap 305. The sealing flow of gas 3255 can aid in transporting contaminant particles 340, for example out of the gap 305, particularly out of the top of the gap 305.

[0065] The sealing gas outlet 325 may be constructed and arranged, for example directed, such that the sealing flow of gas 3255 is directed with a component away from the substrate W. As illustrated in Figure 9 this may not be the case. In an embodiment the sealing flow of gas 3255 of the sealing gas outlet 325 is directed such that the sealing flow of gas 3255 impinges orthogonally on a surface of the projection 307. Additionally, the sealing flow of gas 3255 may have areas which flow up and down relative to the sealing gas outlet 325.

[0066] The sealing gas outlet 325 may be a slit or a series of discrete outlets. The length of the projection 307, which is effective to reduce the gap within tolerance, is at least as long (in the Z-direction) as the movement of the first gas shower module 320 in the Z-direction. In an embodiment, whatever the position of the first gas shower module 320 the sealing flow of gas 3255 will impinge upon the projection 307.

[0067] In an embodiment the projection 307 is not present and the sealing flow of gas 3255 impinges directly on a surface of the projection system module 310. In an embodiment the sealing gas outlet is formed in the projection system module 310 and, if present, the projection 307 is formed on the first gas shower module 320.

[0068] An exhaust opening 342 may be provided in the gap 305. In an embodiment the exhaust opening 342 is in a top surface of the projection 307. Additionally or alternatively an exhaust opening may be present in a side wall of the projection system module 310 and/or gas shower module 320. The exhaust opening 342 is attached to an underpressure source. Thereby contaminant particles 340 which approach the exhaust opening 342 can be removed. For example, at a distance close to the side walls of the projection system module 310 or gas shower module 320, the velocity of the gas flow 3255 may be low. As a result contaminant particles 340 may still fall downwards, even in the absence of a downwards flow 302.

[0069] The top surface of the projection 307 can act as a particle collector. The underpressure source to which the exhaust opening 342 is connected may be continuously on or may be periodically actuated.

[0070] One or more exhaust openings 342 may be provided with or without a sealing gas outlet 325.

[0071] Although the risk of a contaminant particle 340 falling between the gap 305 of the projection sealing module 310 and the second gas shower module 330 is less (because the second gas shower module 330 does not substantially move in the Z direction), a similar arrangement described above with reference to Figure 9 may additionally or alternatively be provided between the second gas shower module 330 and the projection system module 310.

[0072] The gas provided out of the sealing gas outlet 325 is desirably filtered gas and may additionally be humidified and/or temperature conditioned. The gas supplied out of sealing gas outlet 325 may be the same as the gas supplied out of gas shower outlets 3222. The gas source is illustrated in Figure 9 as gas source 3251.

[0073] The gap between the first gas shower module 320 and projection 307 (or between projection 307 and projection system module 310 or between projection 307 and second gas shower module 330) could be as small as possible but may be of the order of 5-20 mm, typically 10 mm.

[0074] A controller 3252 is provided to control the flow rate of gas out of the sealing gas outlet 325 and/or into exhaust opening 342. The gas flow is such that it is effective to block/transport contaminant particles 340 away from the substrate W out of the gap 305 between the projection system module 310 and the gas shower module 320.

[0075] Figure 10 illustrates an embodiment which is the same as the embodiment of Figure 9 except as described below. In Figure 10 a deflector 350 is attached to the first gas shower module 320 above the projection 307. This creates a tortuous path along which contaminant particles 340 would need to be transported in order to fall onto the top surface of the substrate W. Additionally, the combination of the deflector 350 and projection 307 are effective to narrow/lengthen the narrow part of the gap 305 between the projection system module 310 and first gas shower module 320. This is effective to accelerate the sealing flow of gas 3255 away from the substrate W and to bend the contaminant carrying gas flow 3021 to transport the contaminant particle 340 to a position in the machine where its presence is not critical. In an embodiment an exhaust 341 which is connected to an underpressure source is provided to collect the particle 340. The exhaust 341 is controlled by controller 3252. The deflector 350 may be an extension of a top surface of the first gas shower module 320 or may project out of a side wall of the gas shower module 320. In an embodiment the deflector 350 is provided on the projection system module 310 or gas shower module 320, on which the projection 307 is not formed.

[00761 Figure 11 illustrates a further embodiment of the present invention which is the same as that of Figure 9 except as described below.

[0077] In the embodiment of Figure 11 a diverting gas outlet 312 is provided in the projection system module 310. The diverting gas outlet 312 is provided under the projection 307 and/or under the sealing gas outlet 325. A diverting flow of gas 3121 is provided out of the diverting gas outlet 312. The gas exiting outlet 312, under control of controller 3252, for example, is filtered gas. In an embodiment the gas exiting the diverting gas outlet 312 is humidified and/or temperature conditioned gas.

[0078] The diverting flow of gas 3121 is provided in a direction with a component towards the gas shower module 320. Desirably the diverting flow of gas 3121 is at a level below the bottom of the gas shower module 320. A contaminant particle 340 which finds its way through the gap 305 can be deflected away from the top surface of the substrate W by the diverting flow of gas 3121. That is, the contaminant particle 340 will be carried by the diverting flow of gas 3121 away from the projection system module 310 into the flow of gas 322 of the gas shower module 320. The contaminant particle 340 is carried to a part of the apparatus where the presence of the contaminant particle 340 is not critical.

[0079] In an embodiment the controller 3252 generates a flow of gas out of diverting gas outlet 312 when the substrate W is not under the gap 305 between the gas shower module 320 and projection system module 310. That is, the diverting flow of gas 3121 is only present when the substrate table 2 is moving out from under the gap 305 as illustrated in Figure 11, or is not under the gap 305.

[0080] A further embodiment is illustrated in Figure 12. The embodiment of Figure 12 is based on a combination of the embodiments of Figures 10 and 11. That is, the embodiment of Figure 12 comprises both the deflector 350 and the diverting gas outlet 312. The operation of both components is the same as that described with reference to Figures 10 and 11 above respectively.

[0081] Any concept mentioned above in relation to the gap 305 between the projection system module 310 and the first gas shower module 320 may be applied in isolation or in any combination to the gap 305 between the projection system module 310 and the second gas shower module 330.

[0082] As will be clear from the above, an embodiment of the present invention, in particular the sealing gas outlet and associated flow of gas, may be provided between any two components of an apparatus through which the passage of a contaminant particle might be undesirable.

[0083] In a variation of the above described embodiments, a partitioning wall, for example a stationary partitioning wall, may be provided in the gap 305. A sealing gas outlet (and optionally at least one of a diverting gas outlet, projection and deflector) may be provided between the gas shower module 320, 330 and the partitioning wall and between the partitioning wall and the projection system module 310.

[0084] In an apparatus according to an embodiment of the present invention, a plurality of beams of radiation are divided into separate groups, each associated with a particular range of radiation wavelengths. A different response of a dispersion element to the different wavelengths is used in order to bring these plurality of beams of radiation closer together. However, the beams of radiation associated with each group may also respond differently from each other when passing through other optical elements within the projection system. Accordingly, in an embodiment, the projection system may include at least one chromatic correction element that is configured to at least partially compensate for a difference in the response of the optical elements of the projection system other than the dispersion element due to the difference in wavelength between the groups of radiation beams.

[0085] For example, in the absence of chromatic correction, there may be a focus error between the radiation beams of each group of radiation beams. The chromatic correction element may therefore be a section of material, appropriately selected to have a variation in the refractive index for each of the radiation wavelengths used, in order to compensate for this error.

[0086] Alternatively or additionally, such focus errors, caused by variations between the radiation wavelength of the groups of radiation beams, may be minimized by adjusting the optical path length between a radiation source of each group of radiation beams and the dispersion element.

[0087] The dispersion element and any chromatic correction element, where used, may be arranged in any of a number of different locations within the apparatus.

[0088] In an embodiment having a projection system with at least a stationary part and a moving part, the dispersion element may be mounted to the stationary part.

[0089] In an embodiment, the dispersion element may be arranged to be the first optical element within the projection system, or one of the first few elements within the projection system. By arranging the dispersion element in this way. The construction of the subsequent optical elements within the projection system may benefit from the separation between the plurality of radiation beams having been reduced.

[0090] Although embodiments have been described above with reference to the dispersion element as a part of the projection system, this is merely an exemplary arrangement and the dispersion element may be provided at other locations within the apparatus. In an embodiment, the dispersion element may be provided between a plurality of radiation sources, configured to provide a plurality of radiation beams, and the one or more patterning devices configured to impart a pattern to the plurality of radiation beams.

[0091] In an embodiment, the chromatic correction element, where used, may be the final optical element within the projection system or one of the final elements.

[0092] 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.

[0093] Although specific reference may be made in this text to the use of a 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 multilayer 1C, so that the term substrate used herein may also refer to a substrate that already contains one or multiple processed layers.

[0094] 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.

[0095] 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.

CLAUSES

1. An exposure apparatus, comprising: a projection system module, configured to project a radiation beam onto a substrate; a gas shower module, configured to provide a flow of gas onto a top surface of a substrate when uncovered, in plan, by the projection system module; and a sealing gas outlet to provide a sealing flow of gas directed in a direction from the projection system module towards the gas shower module, or vice versa.

2. The exposure apparatus of clause 1, wherein the sealing flow of gas is directed upwards.

3. The exposure apparatus of clause 1 or clause 2, wherein the gas shower module includes a substrate handler configured to load a substrate onto a substrate table to support the substrate.

4. The exposure apparatus of clause 3, wherein the substrate handler is configured to move in a direction substantially parallel to an optical axis of the projection system module and the sealing gas outlet is attached to the substrate handler.

5. The exposure apparatus of any preceding clause, wherein the projection system module or gas shower module on which the sealing gas outlet is not provided includes a projection onto which the sealing flow of gas is directed.

6. The exposure apparatus of any preceding clause, wherein the projection system module or gas shower module on which the sealing gas outlet is provided includes a deflector attached above the gas outlet and extending towards the projection system module or gas shower module on which the sealing gas outlet is not provided.

7. The exposure apparatus of any preceding clause, further comprising a gas source to form the flow of gas onto the top surface of the substrate and to form the sealing flow of gas.

8. The exposure apparatus of clause 7, wherein the gas source is a source of filtered gas.

9. The exposure apparatus of clause 7 or clause 8, wherein the gas source is a source of humidified and/or temperature conditioned gas.

10. The exposure apparatus of any preceding clause, further comprising a controller configurred to control the flow rate of gas out of the sealing gas outlet such that the sealing flow is effective to transport contaminant particles away from the substrate and/or out of a gap between the projection system module and the gas shower module.

11. The exposure apparatus of any preceding clause, wherein the sealing gas outlet comprises one or more outlets substantially extending, in plan, along the length of facing surfaces of the projection system module and gas shower module.

12. The exposure apparatus of any preceding clause, further comprising a diverting gas outlet on the projection system module at a level below the sealing gas outlet and configured to provide a diverting flow of gas in a direction with a component towards the gas shower module.

13. The exposure apparatus of clause 12, further comprising a controller configured to control the flow of gas out of the diverting gas outlet to occur when the substrate is not under a gap between the gas shower module and projection system module.

14. The exposure apparatus of any preceding clause, further comprising an exhaust opening connected to an underpressure source.

15. The exposure apparatus of clause 14, wherein the exhaust opening is formed in a gap between the projection system module and the gas shower module.

16. A device manufacturing method comprising: using a projection system module to project a radiation beam onto a substrate; using a gas shower module to provide a flow of gas onto a top surface of a substrate when uncovered, in plan, by the projection system module; and providing a sealing flow of gas which is directed in a direction from the projection system module towards the gas shower module, or vice versa.

Claims (1)

A lithography device comprising: an exposure 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.