Method and system for maskless lithography

Abstract

A method of exposing a substrate with a patterned radiation beam, comprising: providing a radiation beam; imposing on the radiation beam by an array of individually controllable elements; generating a patterned radiation beam from the radiation beam by tilting the individually controllable elements between different positions about a tilt axis; projecting the patterned radiation beam towards the substrate; and scanning the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, where the tilt axes of the individually controllable elements are substantially perpendicular to the scan direction.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Application No. 20156258.4, filed February 7, 2020, which is incorporated by reference in its entirety into this specification.

[0002] The present disclosure relates to methods and systems for maskless lithography. [Background technology]

[0003]

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays, and other devices or structures with fine features. In a conventional lithographic apparatus, a patterning device, which may also be referred to as a mask or reticle, may be used to create a circuit pattern corresponding to an individual layer of the IC, flat panel display, or other device. This pattern may be transferred onto (part of) the substrate (e.g. a silicon wafer or a glass plate), for example by imaging onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0004]

[0004] Instead of a circuit pattern, the patterning device can 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, which comprises an array of individually addressable elements that generate the circuit or other applicable pattern. The 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 at less cost.

[0005]

[0005] Thus, a maskless system includes a programmable patterning device (e.g., a spatial light modulator, a contrast device, etc.) that is programmed (e.g., electronically or optically) to form the desired patterned beam using an array of individually addressable elements. Types of programmable patterning devices include micromirror arrays, liquid crystal display (LCD) arrays, grating light valve arrays, etc. Summary of the Invention

[0006] It is desirable to improve the performance of lithographic apparatus that include programmable patterning devices instead of masks or reticles.

[0007]

[0007] According to one aspect of the present invention, Providing a beam of radiation; imparting a radiation beam with an array of individually controllable elements; and generating a patterned beam of radiation from the beam of radiation by tilting the individually controllable elements between different positions about a tilt axis; projecting a patterned beam of radiation towards a substrate; scanning the substrate in the scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, with tilt axes of the individually controllable elements being substantially perpendicular to the scan direction; There is provided a method for exposing a substrate with a patterned beam of radiation, comprising:

[0008] According to another aspect of the present invention, there is provided a system for projecting a patterned beam of radiation onto a substrate, the system comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a stage device configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; The tilt axes of the individually controllable elements are substantially perpendicular to the scan direction.

[0009] According to another aspect of the invention, there is provided a system for projecting a patterned beam of radiation onto a substrate, the system comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a stage device configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; a projection system comprising a microlens array, The microlens array is configured to project a first two-dimensional pattern of radiation spots and the first two-dimensional pattern of radiation spots onto a substrate; a width of the first two-dimensional pattern in a direction perpendicular to the scanning direction substantially corresponds to a width of the second two-dimensional pattern in a direction perpendicular to the scanning direction; A length of the first two-dimensional pattern in the scanning direction substantially corresponds to a length of the second two-dimensional pattern in the scanning direction, and the first two-dimensional pattern and the second two-dimensional pattern are spaced apart from each other in the scanning direction.

[0010] According to another aspect of the present invention, there is provided a method of controlling a radiation dose applied to a substrate, the method comprising: modulating the radiation beam according to a predetermined profile over time, the profile comprising a plurality of different intensity levels of the radiation beam; imparting a modulated radiation beam by the array of individually controllable elements to generate a patterned modulated radiation beam by tilting the individually controllable elements between different positions about a tilt axis; and projecting a patterned modulated beam of radiation towards a substrate; scanning the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, thereby exposing a portion of the substrate to the patterned modulated radiation beam; The step of imparting a modulated radiation beam includes: Determining a tilt sequence of an element of the array of controllable elements based on a required radiation dose for the portion of the substrate and a predetermined profile over time to expose the portion of the substrate to a sequence of a plurality of different intensity levels.

[0011] According to another aspect of the present invention, there is provided a system for projecting a patterned beam of radiation onto a substrate, the system comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a radiation beam modulator configured to modulate a radiation beam according to a predetermined profile over time, the profile comprising a plurality of different intensity levels of the radiation beam; the array of individually controllable elements is configured to impart a modulated radiation beam to generate a patterned modulated radiation beam by tilting the individually controllable elements between different positions about a tilt axis; The system further comprises: a stage device configured to hold a substrate and configured to expose the substrate to the patterned radiation beam, thereby scanning the substrate in a scan direction across the patterned modulated radiation beam to expose a portion of the substrate to the patterned modulated radiation beam; a control unit configured to determine a tilt sequence of an element of the array of controllable elements based on a required radiation dose of the portion of the substrate and a predetermined profile over time to expose the portion of the substrate to a sequence of a plurality of different intensity levels; Equipped with.

[0012] According to another aspect of the present invention, there is provided a system for projecting a patterned beam of radiation onto a substrate, the system comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a stage device configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; a projection system configured to receive the patterned beam of radiation; The projection system is A first microlens array; A second microlens array; and a pinhole array; and the first microlens array is configured to receive the patterned beam of radiation and project the patterned beam of radiation onto the second microlens array; the second microlens array is configured to project the received patterned beam of radiation onto the substrate; the pinhole array is disposed in an optical path of the patterned beam of radiation between the first microlens array and the second microlens array; The pinhole array is configured to limit crosstalk between adjacent radiation spots projected onto the substrate. [Brief description of the drawings]

[0013]

[0013] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present invention and, together with the specification, serve to explain the principles of embodiments of the present invention and to enable those skilled in the art to make and use those embodiments.

[0014] [Figure 1]

[0014] FIG. 1 illustrates a schematic side view of a part of a lithographic apparatus according to one embodiment. [Diagram 2]

[0015] 1 depicts a schematic top view of a part of a lithographic apparatus according to an embodiment; [Diagram 3]

[0016] 1 depicts a schematic top view of a part of a lithographic apparatus according to an embodiment; [Figure 4]

[0017] 2A illustrates a schematic representation of a two-dimensional pattern of radiation spots. [Diagram 5]

[0018] 2 shows a schematic representation of a regular two-dimensional pattern of radiation spots. [Figure 6] 1 illustrates a schematic representation of an irregular two-dimensional pattern of radiation spots; [Figure 7]

[0019] 1A and 1B illustrate schematic diagrams of a top view of a two-dimensional array of controllable elements; [Figure 8]

[0020] 1 illustrates an irregular pattern of radiation spots produced by having a tilt axis substantially perpendicular to the scan direction. [Figure 9]

[0021] 1 illustrates generally a top view of a pattern of emissive dots comprising a first two-dimensional pattern of emissive dots and a second two-dimensional pattern of emissive dots. [Figure 10]

[0022] 2 shows a schematic flow chart of a method according to a third aspect of the present invention; [Figure 11]

[0023] 2 illustrates diagrammatically a profile or modulation profile that can be applied to a radiation beam; [Figure 12]

[0024] 1 illustrates diagrammatically a radiation beam propagating along a Y or scan direction. [Figure 13a]

[0025] 10A-10C show schematic examples of tilt sequences of controllable elements and the resulting applied radiation profiles; [Figure 13b]

[0025] Figure 1 shows schematic examples of tilt sequences of controllable elements and the resulting applied radiation profiles. [Figure 14]

[0026] 5 illustrates diagrammatically part of a projection system applicable in a system according to a fourth aspect of the invention;

[0015]

[0027] One or more embodiments are now described with reference to the accompanying drawings, where like reference numbers can indicate identical or functionally similar elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016]

[0028] Described herein are various embodiments of a lithographic apparatus, in particular a system for use in a maskless lithographic apparatus, a method for controlling a radiation dose applied to a substrate, and a lithographic apparatus that is maskless such that no traditional mask is required to expose, for example, an IC or a flat panel display.

[0017]

[0029] In one embodiment, the lithographic apparatus is highly flexible. In one embodiment, the lithographic apparatus is scalable to substrates of different sizes, types, and characteristics. Thus, the lithographic apparatus can enable multiple applications (e.g. ICs, flat panel displays, packaging, etc.) with a single lithographic apparatus or with multiple lithographic apparatuses that mostly use a common lithographic apparatus platform.

[0018]

[0030] 1 illustrates generally a part of a lithographic projection apparatus 100 according to one embodiment. The apparatus 100 includes a patterning device 104, an object holder 106 (such as an object table, e.g. a substrate table), and a projection system 108.

[0019]

[0031] In an embodiment, the patterning device 104 comprises a plurality of individually addressable elements 102 for modulating radiation to apply a pattern to the beam 110. In an embodiment, the positions of the plurality of individually addressable or controllable elements 102 may be fixed relative to the projection system 108. However, in an alternative arrangement, the plurality of individually addressable or controllable elements 102 may be connected to a positioning device (not shown) for precisely positioning one or more of them according to certain parameters (e.g. relative to the projection system 108). In an embodiment, the plurality of individually controllable elements are arranged in an array, e.g. a two-dimensional array. In an embodiment, the individually controllable elements are reflective elements such as mirrors. In accordance with the invention, the patterning device may be configured to impart to a radiation beam, e.g. provided by a radiation source, to generate a patterned radiation beam. In an embodiment, the patterning device 104 may comprise a programmable mirror array, the positions of individual mirrors of the programmable mirror array being controllable. In particular, the orientation of the individual mirrors of the programmable mirror array, and in general of the patterning device, may be adjusted by tilting the individual mirrors.

[0020]

[0032] The lithographic apparatus 100 comprises an object holder 106. In this embodiment, the object holder comprises an object table 106 for holding a substrate 114 (e.g. a resist-coated silicon wafer or a glass substrate). The object table 106 may be movable in up to six degrees of freedom (e.g. in X and / or Y direction) and may be connected to a positioning device 116 for accurately positioning the substrate 114 according to predefined parameters. For example, the positioning device 116 may accurately position the substrate 114 relative to the projection system 108 and / or the patterning device 104. In an embodiment, the movement of the object table 106 may be realized by the positioning device 116 comprising a long-stroke module (coarse positioning) and optionally a short-stroke module (fine positioning). Both modules are not explicitly shown in FIG. 1 . A similar system may be used to position the individually addressable elements 102 so that, for example, the individually addressable elements 102 are movable in up to six degrees of freedom (e.g. in the X and / or Y directions), e.g. to scan in a direction substantially parallel to the scanning direction of the object table 106 and optionally to step in a direction perpendicular to the scanning direction. Alternatively / additionally, the beam 110 may be movable while the object table 106 and / or the individually addressable elements 102 may have fixed positions to provide the necessary relative movement. Such an arrangement may help to limit the size of the apparatus.

[0021]

[0033] In an embodiment, which may be applicable, for example, in the manufacture of flat panel displays, the object table 106 may be stationary and the positioning device 116 is configured to move the substrate 114 relative to (e.g., over) the object table 106. For example, the object table 106 may be provided with a system for scanning the entire substrate 114 at a substantially constant speed. The object table 106 may then be provided with a number of openings in its flat top surface through which gas is supplied to provide a gas cushion that can support the substrate 114. This is conventionally referred to as a gas bearing mechanism. The substrate 114 is moved over the object table 106 using one or more actuators (not shown) that can precisely position the substrate 114 with respect to the path of the beam 110. Alternatively, the substrate 114 may be moved relative to the object table 106 by selectively starting and stopping the passage of gas through the openings. In an embodiment, the object holder 106 may be a roll system on which the substrate is wound and the positioning device 116 may be a motor for rotating the roll system to provide the substrate on the object table 106.

[0022]

[0034] In one embodiment, a lithographic apparatus according to the invention comprises a projection system 108 (e.g. a catadioptric system with lens elements made of quartz, glass, plastic (e.g. COC) and / or CaF2 lens system or optical element, or a mirror system, or an optical element with an additional layer of polymer (e.g. glass element), or an optical element with flat and spherical surfaces that can be transformed into an aspheric shape, e.g. with a polymer layer), which can be used to project the patterned beam modulated by the individually addressable elements 102 onto a target portion 120 (e.g. one or more dies) of a substrate 114. The projection system 108 can image the pattern provided by the plurality of individually addressable elements 102 such that the pattern is coherently formed on the substrate 114. Alternatively, the projection system 108 can project an image of a secondary source, with the plurality of individually addressable elements 102 elements acting as shutters.

[0023]

[0035] In this regard, the projection system may comprise a focusing element or a number of focusing elements (generally referred to herein as a lens array), such as a microlens array (known as an MLA) or a Fresnel lens array, for example to form the secondary sources and image the spots onto the substrate 114. In an embodiment, the lens array (such as an MLA) comprises at least 10 focusing elements, such as at least 100 focusing elements, at least 1,000 focusing elements, at least 10,000 focusing elements, at least 100,000 focusing elements, or at least 1,000,000 focusing elements. In an embodiment, the number of individually addressable elements in the patterning device is equal to or greater than the number of focusing elements in the lens array. In one embodiment, the lens array comprises a plurality of focusing elements, where at least one focusing element is optically associated with one or more of the individually addressable elements of the array of individually addressable elements, e.g., with only one of the individually addressable elements of the array of individually addressable elements, or with two or more, e.g., three or more, five or more, ten or more, twenty or more, twenty-five or more, thirty-five or more, or fifty or more of the individually addressable elements of the array of individually addressable elements. In one embodiment, at least one focusing element of the plurality of optical elements is optically associated with fewer than 5,000, e.g., fewer than 2,500, fewer than 1,000, fewer than 500, or fewer than 100 individually addressable elements.

[0024]

[0036] In one embodiment, the lens array comprises two or more (eg, greater than 1,000, a majority, or nearly all) focusing elements each in optical association with a plurality of individually addressable elements in the two-dimensional array.

[0025]

[0037] In one embodiment, patterning device 104 is movable at least towards and away from the substrate, for example by use of one or more actuators. Being able to move the patterning device towards and away from the substrate allows, for example, for adjusting focus without moving the substrate or the lens array (e.g., localized focus adjustment on a non-flat substrate).

[0026]

[0038] In one embodiment, the lens array comprises plastic focusing elements (which may be easy to fabricate, e.g., by injection molding, and / or affordable), where, for example, the wavelength of the radiation is about 400 nm or greater (e.g., 405 nm). In one embodiment, the wavelength of the radiation is selected from the range of about 350 nm to 500 nm, e.g., about 375 to 425 nm. In one embodiment, the lens array comprises quartz or glass focusing elements.

[0027]

[0039] In one embodiment, each of the focusing elements or more than one of the focusing elements may be an asymmetric lens (e.g., having one or more asymmetric faces). The symmetry may be the same for each of the multiple focusing elements or may be different for one or more of the multiple focusing elements than for one or more other of the multiple focusing elements. An asymmetric lens may facilitate converting an elliptical radiation output into a circular projected spot or vice versa.

[0028]

[0040] In one embodiment, the focusing element has a high numerical aperture (NA) arranged to project radiation out of focus onto the substrate to achieve a low NA for the system. Higher NA lenses may be more economical, more common, and / or of better quality than available low NA lenses. In one embodiment, the low NA is 0.3 or less, and in one embodiment 0.18, 0.15, or less. Thus, a higher NA lens has an NA greater than the design NA of the system, for example greater than 0.3, greater than 0.18, or greater than 0.15.

[0029]

[0041] In one embodiment, projection system 108 is separate from patterning device 104, but this is not necessary. Projection system 108 may be integral to patterning device 104. For example, a lens array block or plate may be attached to (integral with) patterning device 104. In one embodiment, the lens array may be in the form of individual, spatially separated lenslets, each lenslet being attached to (integral with) one or more individually addressable elements of patterning device 104, as described in more detail below.

[0030]

[0042] Optionally, the lithographic apparatus may comprise a radiation system for supplying radiation (e.g. ultraviolet (UV) radiation) to the plurality of individually addressable elements 102. In an embodiment, such a radiation system comprises an illumination system (illuminator) configured to receive radiation from a radiation source. The illumination system comprises one or more of the following elements: a radiation delivery system (e.g. suitable directing mirrors), a radiation conditioning device (e.g. a beam expander), an adjustment device for setting the angular intensity distribution of the radiation (generally at least the outer and / or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator is adjustable), an integrator, and / or a condenser. The illumination system may be used to adjust the radiation that will be provided to the individually addressable elements 102 such that it has a desired uniformity and intensity distribution in its cross-section. The illumination system may be arranged to split the radiation into a plurality of sub-beams, which may for example each be associated with one or more of the plurality of individually addressable elements. The radiation may be split into sub-beams, for example using a two-dimensional diffraction grating. As used herein, the terms "beam of radiation" and "beam of radiation" include, but are not limited to, the situation where the beam is composed of multiple such sub-beams of radiation.

[0031]

[0043] The radiation system may also include a radiation source (e.g. an excimer laser) for generating radiation for delivery to or by the plurality of individually addressable elements 102. The radiation source and lithographic apparatus 100 may be separate entities, for example when the radiation source is an excimer laser. In such a case, the radiation source is not considered to form part of lithographic apparatus 100, and radiation is transmitted from the radiation source to the illuminator. In other cases, the radiation source may be an integral part of lithographic apparatus 100, for example when the radiation source is a mercury lamp.

[0032]

[0044] In one embodiment, the radiation source, which in an embodiment may be a plurality of individually addressable elements 102, may provide radiation having a wavelength of at least 5 nm, e.g., at least 10 nm, at least 50 nm, at least 100 nm, at least 150 nm, at least 175 nm, at least 200 nm, at least 250 nm, at least 275 nm, at least 300 nm, at least 325 nm, at least 350 nm, or at least 360 nm. In one embodiment, the radiation has a wavelength of at most 450 nm, e.g., at most 425 nm, at most 375 nm, at most 360 nm, at most 325 nm, at most 275 nm, at most 250 nm, at most 225 nm, at most 200 nm, or at most 175 nm. In one embodiment, the radiation has a wavelength including 436 nm, 405 nm, 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, 126 nm, and / or 13.5 nm. In one embodiment, the radiation comprises a wavelength of approximately 365 nm or approximately 355 nm. In one embodiment, the radiation comprises a broad band of wavelengths, for example including 365 nm, 405 nm, and 436 nm. A 355 nm laser source may be used. In one embodiment, the radiation has a wavelength of about 405 nm.

[0033]

[0045] During operation of the lithographic apparatus 100 , radiation is incident on the patterning device 104 (eg, a plurality of individually addressable elements) from a radiation system (an illumination system and / or a radiation source) and is modulated by the patterning device 104 .

[0034]

[0046] After the patterned beam 110 is produced by the plurality of individually addressable elements 102 , it passes through the projection system 108 , which focuses the beam 110 onto a target portion 120 on a substrate 114 .

[0035]

[0047] With the aid of the positioning device 116 (and optionally a position sensor 134 on the base 136, such as an interferometric measuring device, linear encoder, or capacitive sensor receiving the interfering beam 138), the substrate 114 can be precisely moved, for example, to position the various target portions 120 in the path of the beam 110. If used, the positioning device for the multiple individually addressable elements 102 can be used to precisely correct the position of the multiple individually addressable elements 102 relative to the path of the beam 110, for example during a scan.

[0036]

[0048] Although lithographic apparatus 100 in one embodiment is described herein as being configured to expose resist on a substrate, apparatus 100 may also be used to project a patterned beam 110 for use in resistless lithography.

[0037]

[0049] Lithographic apparatus 100 may be of a reflective type (e.g. employing reflective individually addressable elements) or alternatively, the apparatus may be of a transmissive type (e.g. employing transmissive individually addressable elements).

[0038]

[0050] The depicted apparatus 100 can be used in one or more modes as follows.

[0039]

[0051] 1. In step mode, the individually addressable elements 102 and the substrate 114 are kept essentially stationary while the entire patterned radiation beam 110 is projected onto the target portion 120 in one go (i.e., a single static exposure). The substrate 114 is then shifted in the X and / or Y directions so that a different target portion 120 can be exposed to the patterned radiation beam 110. In step mode, the maximum size of the exposure field limits the size of the target portion 120 that can be imaged in a single static exposure.

[0040]

[0052] 2. In scan mode, the individually addressable elements 102 and the substrate 114 are scanned synchronously (i.e., a single dynamic exposure) while the patterned radiation beam 110 is projected onto the target portion 120. The velocity and direction of the substrate relative to the individually addressable elements may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, and the length of the scanning motion determines the length (in the scanning direction) of the target portion.

[0041]

[0053] 3. In pulse mode, the individually addressable elements 102 are kept essentially stationary and the entire pattern is projected onto the target portions 120 of the substrate 114 using pulsing (e.g. provided by a pulsed radiation source or by pulsing the individually addressable elements). The substrate 114 is moved at an essentially constant speed to cause the patterned beam 110 to scan a line across the substrate 114. The pattern provided by the individually addressable elements is updated as necessary between pulses, and the pulses are timed to expose successive target portions 120 at the required locations on the substrate 114. As a result, the patterned beam 110 may be scanned across the substrate 114 to expose the entire pattern of a strip of the substrate 114, and this process is repeated line by line until the entire substrate 114 has been exposed.

[0042]

[0054] 4. Continuous scan mode is essentially the same as pulsed mode, except that the substrate 114 is scanned at a substantially constant speed relative to the modulated beam of radiation B, and the pattern on the array of individually addressable elements is updated as the patterned beam 110 is scanned across and exposes the substrate 114. A substantially uniform radiation source or a pulsed radiation source may be used, synchronized with the updating of the pattern on the array of individually addressable elements.

[0043]

[0055] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

[0044]

[0056] FIG. 2 illustrates a schematic top view of a part of a lithographic apparatus according to an embodiment for use with a substrate (e.g., a 300 mm wafer). As shown in FIG. 2, the lithographic apparatus 100 comprises a substrate table 106 for holding a substrate 114. Associated with the substrate table 106 is a positioning device 116 for moving the substrate table 106 at least in the X direction, illustrated by arrow 123. Optionally, the positioning device 116 may move the substrate table 106 in the Y direction and / or the Z direction. The positioning device 116 may also rotate the substrate table 106 about the X direction, the Y direction, and / or the Z direction. Thus, the positioning device 116 may provide up to six degrees of freedom of movement. In an embodiment, the substrate table 106 provides only movement in the X direction. The advantage is lower cost and less complexity.

[0045]

[0057] The lithographic apparatus 100 further comprises a plurality of individually addressable elements 102 arranged on a frame 160. The frame 160 may be mechanically isolated from the substrate table 106 and its positioning device 116. The mechanical isolation may be provided, for example, by grounding the frame 160 or by connecting it to a rigid base that is separate from the frame of the substrate table 106 and / or its positioning device 116. Additionally or alternatively, a damper may be provided between the frame 160 and the structure to which it is connected, whether that structure is the ground, a rigid base, or a frame supporting the substrate table 106 and / or its positioning device 116.

[0046]

[0058] In this embodiment, each of the individually addressable elements 102 is a radiation emitting diode, e.g., an LED. For simplicity, FIG. 2 shows three rows of individually addressable elements 102 extending along the Y direction (and spaced apart in the X direction), with each row having enough columns to extend across the width of the substrate in this embodiment. More rows of individually addressable elements 102 may be disposed on the frame 160. In one embodiment, each of the individually addressable elements 102 is configured to provide multiple radiation beams. In one embodiment, each of the individually addressable elements 102 illustrated in FIG. 2 comprises multiple individually addressable elements 102 (and thus each circle labeled 102 in FIG. 2 represents multiple individually addressable elements 102). In one embodiment, one or more rows of individually addressable elements 102 are offset in the Y direction from adjacent rows of individually addressable elements 102 as shown in FIG. 2. In one embodiment, the individually addressable elements 102 are substantially stationary. That is, there is little or no movement during projection.

[0047]

[0059] Lithographic apparatus 100, and in particular individually addressable elements 102, may be arranged to provide pixel grid imaging, as described in more detail herein. However, in one embodiment, lithographic apparatus 100 may not provide pixel grid imaging. Rather, lithographic apparatus 100 may project radiation of individually addressable elements 102 onto a substrate such that it forms a substantially continuous image upon projection onto the substrate rather than forming individual pixels upon projection onto the substrate.

[0048]

[0060] The elements 150 of the lithographic apparatus 100 illustrated in Figure 2 may comprise an alignment sensor, a level sensor, or both. For example, in one embodiment, the lithographic apparatus 100 comprises an alignment sensor 150. The alignment sensor is used to determine the alignment between the substrate 114 and the individually addressable elements 102, for example before and / or during exposure of the substrate 114. The results of the alignment sensor 150 may be used by a controller of the lithographic apparatus 100 to control the positioning device 116, for example to position the substrate table 106 to improve alignment. Additionally or alternatively, the controller may, for example, in response to signals from the sensor 150, control a positioning device associated with the individually addressable elements 102 to position one or more of the individually addressable elements 102 (e.g., including positioning one or more of the elements 102 relative to one or more other elements 102) to improve alignment, and / or in response to signals from the sensor 150, control a deflector associated with the individually addressable elements 102 to position one or more of the beams (e.g., including positioning one or more of the beams relative to one or more other beams) to improve alignment. In one embodiment, the alignment sensor 150 may include pattern recognition functionality / software to perform the alignment.

[0049]

[0061] In an embodiment, the lithographic apparatus 100 additionally or alternatively comprises a level sensor 150. The level sensor 150 is used to determine whether the substrate 106 is level for the projection of the pattern from the individually addressable elements 102. The level sensor 150 can determine level before and / or during exposure of the substrate 114. The results of the level sensor 150 can be used by a controller of the lithographic apparatus 100 to control the positioning device 116, for example, to position the substrate table 106 to improve leveling. Additionally or alternatively, the controller can, for example, in response to a signal from the sensor 150, control a positioning device associated with the projection system 108 (e.g. a lens array) to position an element of the projection system 108 (e.g. a lens of the lens array or a smaller lens array, including positioning a lens of the lens array or a smaller lens array relative to another lens of the lens array or another smaller lens array) to improve leveling. In one embodiment, the level sensor may operate by projecting an ultrasonic beam at the substrate 106 and / or may operate by projecting an electromagnetic beam of radiation at the substrate 106 .

[0050]

[0062] In one embodiment, results from the alignment and / or level sensors may be used to modify the pattern provided by the individually addressable elements 102. The pattern may be modified to correct for distortions that may be caused by, for example, optics (if any) between the individually addressable elements 102 and the substrate 114, irregularities in the positioning of the substrate 114, non-uniformity of the substrate 114, etc. Thus, results from the alignment and / or level sensors may be used to modify the projected pattern to provide non-linear distortion correction. Non-linear distortion correction may be useful, for example, for flexible displays that may not have consistent linear or non-linear distortion.

[0051]

[0063] During operation of the lithographic apparatus 100, the substrate 114 is loaded onto the substrate table 106, for example using a robot handler (not shown). The substrate 114 is then displaced in the X direction, indicated by arrow 123, under the frame 160 and the individually addressable elements 102. The substrate 114 is measured by the level and / or alignment sensors 150 and then exposed to a pattern using the individually addressable elements 102. For example, the substrate 114 is scanned through the focal plane (image plane) of the projection system 108 while the substrate is moving and the individually addressable elements 102 are switched at least partially or fully "on" or "off" at the patterning device 104. Features corresponding to the pattern of the patterning device 104 are formed on the substrate 114. In one embodiment, the substrate 114 may be scanned all the way in the positive X direction and then all the way in the negative X direction. In such an embodiment, an additional level and / or alignment sensor 150 may be required on the opposite side of the individually addressable elements 102 for scanning in the negative X direction.

[0052]

[0064] 3 illustrates a schematic top view of a portion of a lithographic apparatus according to an embodiment, for example for exposing a substrate in the manufacture of flat panel displays (e.g. LCD, OLED displays, etc.). Similar to the lithographic apparatus 100 shown in FIG. 2, the lithographic apparatus 100 comprises a substrate table 106 for holding a flat panel display substrate 114, a positioning device 116 for moving the substrate table 106 with up to six degrees of freedom, an alignment sensor 150 for determining the alignment between the individually addressable elements 102 and the substrate 114, and a level sensor 150 for determining whether the substrate 114 is level to the projection of a pattern from the individually addressable elements 102.

[0053]

[0065] The lithographic apparatus 100 further comprises a plurality of individually addressable elements 102 arranged on the frame 160. In this embodiment, each of the individually addressable elements 102 is a radiation emitting diode, e.g., an LED. For simplicity, FIG. 3 shows three rows of individually addressable elements 102 extending along the Y direction, with enough columns to cover the width of the substrate. A larger number of rows of individually addressable elements 102 may be arranged on the frame 160. In an embodiment, each of the individually addressable elements 102 is configured to provide multiple radiation beams. In an embodiment, each of the individually addressable elements 102 illustrated in FIG. 3 comprises multiple individually addressable elements 102 (and thus each circle labeled 102 in FIG. 3 represents multiple individually addressable elements 102). Furthermore, in an embodiment, the multiple rows of individually addressable elements 102 are offset in the Y direction from one or more adjacent rows of individually addressable elements 102, as shown in FIG. 3. The lithographic apparatus 100, and in particular the individually addressable elements 102, may be arranged to provide pixel grid imaging. In one embodiment, the individually addressable elements 102 are substantially stationary, i.e., they do not move significantly during projection.

[0054]

[0066] During operation of the lithographic apparatus 100, a panel display substrate 114 is loaded onto the substrate table 106, for example using a robotic handler (not shown). The substrate 114 is then displaced in the X direction, indicated by arrow 123, under the frame 160 and the individually addressable elements 102. The substrate 114 is measured by level and / or alignment sensors 150 and then exposed to a pattern using the individually addressable elements 102. One or more lenses may be used to project the patterning beam from the individually addressable elements 102 onto the substrate.

[0055]

[0067] As discussed above, the plurality of individually addressable elements 102 are optically associated with a lens of the projection system 108. In one embodiment, the patterned beam from the plurality of individually addressable elements 102 substantially covers the field of view of an associated lens of the projection system 108. In one embodiment, the plurality of individually addressable elements 102 collectively form a two-dimensional emitter array, with each array associated with a single lens of the projection system 108. Thus, in one embodiment, a plurality of emitter arrays are provided, with each array associated with a single lens of a lens array (extending in the XY plane) of the projection system 108. Thus, in one embodiment, a single lens forms all or a portion of the projection system 108 for the array of individually addressable elements 102.

[0056]

[0068] In conventional lithography, a mask or reticle is provided with a pattern to be projected onto a substrate. In such an arrangement, the mask or reticle is used to impart to a radiation beam to form a patterned radiation beam. By synchronously scanning the mask or reticle across the radiation beam and the substrate across the patterned radiation beam, the substrate is exposed to the pattern of the mask or reticle. In maskless lithography, the radiation beam is typically imparted by an array of individually controllable elements, for example individually controllable mirrors that can be tilted. By individually tilting the elements, a patterned radiation beam can be generated. The substrate can be scanned across such a patterned radiation beam. During such a scan, the pattern of the patterned radiation beam can be continuously adjusted to project a desired pattern onto the substrate.

[0057]

[0069] The present invention provides various improvements for maskless lithography systems or apparatus, which may be implemented, for example, in the lithographic apparatus described above.

[0058]

[0070] According to a first aspect of the present invention there is provided a system for use in a maskless lithographic apparatus comprising an array of individually controllable elements configured to impart to a radiation beam a patterned radiation beam by tilting the individually controllable elements between different positions about a tilt axis, Such an array of individually controllable elements may form part of a programmable mirror array or the like.

[0059]

[0071] In such an embodiment, the controllable element may for example be a mirror.

[0060]

[0072] In one embodiment, the array may be, for example, a two-dimensional array of individually controllable mirrors. The system according to the first aspect of the invention further comprises a stage arrangement configured to hold the substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam. To generate the patterned radiation beam, the controllable element, for example a mirror, may be controlled to be positioned in two different positions. In such an arrangement, the controllable element may be brought, for example, to a first position or a second position, where when in the first position the element projects a portion of the radiation beam towards the substrate or towards the projection system and when in the second position the element projects a portion away from the substrate or the projection system. In such an embodiment, the first position may be referred to as the "on" position, whereas the second position may be referred to as the "off" position.

[0061]

[0073] Generally, the patterned radiation beam, when projected onto the substrate, results in a pattern or radiation spot. In the case of a two-dimensional array of controllable elements where all the controllable elements are brought to a first position, this will result in a two-dimensional pattern of radiation spots on the substrate. Such a pattern is shown diagrammatically in FIG.

[0062]

[0074] 4 shows diagrammatically a two-dimensional pattern of radiation spots 400 that may be generated, for example, by positioning a two-dimensional array of controllable elements in an "on" position and projecting an applied radiation beam onto a substrate via a projection system or lens or the like. Ideally, a regular grid pattern of radiation spots should be obtained, in which the distance x between adjacent spots in the x direction is equal for all spots, and the distance y between adjacent spots in the y direction is equal for all spots. Typically, the distances x and y between adjacent spots are greater than the diameter or cross-section of the radiation spots.

[0063]

[0075] To enable each part or location of the substrate to be exposed, the substrate may be displaced or scanned under the pattern of radiation spots in directions slightly offset from the X and Y directions in which the radiation spots are oriented.

[0064]

[0076] In particular, as illustrated in FIG. 4, a scan direction SD may be selected such that each portion or location is scanned by a radiation spot based on the number of spots in the X direction, the distance y between adjacent spots, and the size of the spots. In particular, line 500 shows the trajectory of the radiation spots when the substrate is scanned along the direction SD relative to the array of radiation spots. As can be seen, the entire area of ​​the substrate may be scanned by the selected scan direction. In particular, the scan trajectory of the different radiation spots is such that a pattern with no gaps in the X direction is obtained when the substrate is scanned across the array of radiation spots 400. As will be understood by those skilled in the art, by adjusting and synchronizing the positions of the controllable elements, thereby controlling whether the elements are in an "on" or "off" position and the scanning movement of the substrate, the substrate may be irradiated with any pattern in a maskless manner.

[0065]

[0077] It has been observed by the inventors that in practice a regular grid pattern of radiation spots will not be realized. Rather, it can be observed that the radiation spots will generally be displaced with respect to the desired or expected regular grid pattern. Figures 5 and 6 show the effect of an irregular pattern of radiation spots in a schematic manner. In particular, Figure 5 shows a detailed pattern of radiation spots 600 in a regular pattern, together with the corresponding trajectory 610 of the radiation spots 600 of the left row of spots along the scan direction SD. Figure 6 shows the same pattern of radiation spots 600 as shown in Figure 5, with the two radiation spots of the left row being displaced with respect to their desired positions. In particular, the actual position of radiation spot 600.1 is at the location indicated by circle 620.1, while the actual position of radiation spot 600.2 is at the location indicated by circle 620.2. Radiation spot 600.1 is thus displaced towards the top right corner of the array, while radiation spot 600.1 has a position that is offset towards the bottom left corner of the array. As a result of these shifted positions, the trajectories of the radiation spots are also displaced. In particular, it can be seen that the trajectory 610.1 of radiation spot 600.1 has moved closer to the trajectory 610.3 of radiation spot 600.3, while the trajectory 610.2 of radiation spot 600.2 has moved closer to the trajectory 610.4 of radiation spot 600.4. As a result, during a scanning movement along the direction SD, there will be an overlap of the areas covered by radiation spots 600.1 and 600.3, as well as an overlap of the areas covered by radiation spots 600.2 and 600.4. Such an overlap is undesirable, as it introduces uncertainty as to the actual radiation dose applied to a particular location. It can also be noted that a gap has appeared between the trajectories of radiation spots 600.1 and 600.2, resulting in areas that will not be covered by any of the radiation spots during a scanning movement along the direction SD. As a result, it may not be possible to expose the substrate to the desired radiation pattern.

[0066]

[0078] As illustrated in FIG. 6, the deviation occurring in the radiation spot positions of spots 600.1 and 600.2 has components in both a designated X direction and a designated Y direction, the Y direction substantially corresponding to the scan direction.

[0067]

[0079] It is contemplated that the misalignment that occurs may be attributed to the manner in which known arrays of controllable elements, such as programmable mirror arrays or the like, are constructed.

[0068]

[0080] 7 shows a schematic top view of a two-dimensional array 700 of controllable elements, in particular mirrors 710, whose positions are controllable to thereby control the deflection of a received portion of a radiation beam. In the embodiment shown, the mirrors 700 are substantially rectangular mirrors arranged along X' and Y' directions. When used to pattern a substrate, as described above, the array 700 is typically oriented such that the mirrors arranged along the X' direction provide an array of spots on the substrate along the X direction, and such that the mirrors arranged along the Y' direction provide an array of spots on the substrate along the Y direction, for example as illustrated in Figures 4, 5 and 6.

[0069]

[0081] To change the position of the mirror 710, the mirror is typically tilted. Typically, the tilt axis 720 of the mirror, generally the controllable element, is oriented along the diagonal of the element, as illustrated in FIG. 7. Thus, to bring the mirror 710.1 to a first position, e.g. the "on" position, the mirror 710.1 is tilted about the tilt axis 720 at a first angle. Similarly, to bring the mirror 710.1 to a second position, e.g. the "off" position, the mirror 710.1 is tilted about the tilt axis 720 at a second angle, different from the first angle. It has been observed that the tilt angle at which the mirrors 710 of the array 700 are tilted in the "on" position may not be the same for all mirrors. Thus, the tilt angle obtained when the mirror 710 is positioned in the "on" position may be different. As a result, the part of the radiation beam deflected by the mirror may be deflected in a different direction, causing the resulting pattern or radiation spot on the substrate to be irregular, as illustrated, for example, in FIG. 6.

[0070]

[0082] It has been hypothesized by the inventors that the adverse effects of such irregular patterns may be mitigated by adjusting the orientation of the array 700 of controllable elements 710 relative to the scan direction. In particular, according to a first aspect of the invention, it is proposed to arrange the array of individually controllable elements such that the tilt axes of the elements are substantially perpendicular to the scan direction.

[0071]

[0083] By orienting the tilt axes of the individually controllable elements of the array to be substantially perpendicular to the scan direction of the substrate, variations in the tilt angles of the controllable elements will only result in irregularities in the pattern of radiation spots in the scan direction. This is illustrated in Figure 8.

[0072]

[0084] 8 illustrates a pattern 800 of radiation spots that is generated by positioning a two-dimensional array of individually controllable elements in an "on" position and projecting an applied radiation beam onto a substrate, for example via a projection system or lens. In the illustrated pattern, the dots 800 represent a regular desired pattern of radiation spots. It is further assumed that the tilt axes of the individually controllable elements are oriented such that a variation in the tilt angle of an element that deflects a portion of the radiation beam causes a corresponding displacement of the radiation beam in the scan direction SD. In the illustrated example, a deviation in the tilt angle of the elements that generate radiation spots 800.1 and 800.2 is assumed. In particular, the actual position of radiation spot 800.1 is at the location indicated by circle 820.1, while the actual position of radiation spot 800.2 is at the location indicated by circle 820.2. As can be seen, the actual locations of the radiation spots 820.1 and 820.2 still remain on the trajectory 810 associated with the regular grid pattern 800, the radiation spots 820.1 and 820.2 are merely displaced along the scan direction relative to their desired locations, so that, in contrast to the example shown in Fig. 6, the positions of the trajectories of the different radiation spots are not changed.

[0073]

[0085] Thus, the adverse effects described with reference to FIG. 6 will not occur with the pattern of FIG.

[0074]

[0086] By orienting the tilt angle of the array of individually controllable elements to be substantially perpendicular to the scan direction, the effect is achieved that variations in the tilt angle of the controllable elements of the array of individually controllable elements only cause positional variations in the scan direction of the corresponding radiation spots.

[0075]

[0087] It can further be noted that if the positional variation, e.g. the difference between positions 800.1 and 820.1, is known, the effect of the radiation spot displacement on the patterning or exposure process can be taken into account by adjusting the timing or timing sequence of the corresponding controllable elements.

[0076]

[0088] Thus, the system according to the first aspect of the invention may be characterised by comprising the following features: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; a stage apparatus configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; and The tilt axes of the individually controllable elements are substantially perpendicular to the scan direction.

[0077]

[0089] As discussed above with reference to Figures 4 to 8, a particular orientation of the tilt axis relative to the scan direction allows for more accurate exposure of the substrate to a desired pattern.

[0078]

[0090] With regard to the application of an array of individually controllable elements to apply a radiation beam to generate a patterned radiation beam, it can be pointed out that such arrays are commercially available and may comprise, for example, hundreds of rows and columns of controllable elements. If such an array is applied to expose a substrate and the patterned radiation beam is projected onto the substrate using a microlens array, the large number of available controllable elements may result in an undesirably large microlens array, assuming that the microlens array has a corresponding lens or lenslet for each controllable element of the array. Thus, according to a second aspect of the present invention, a system for projecting a patterned radiation beam onto a substrate is proposed, the system comprising an array of individually controllable elements for generating a patterned radiation beam and a projection system comprising a microlens array. According to the second aspect of the present invention, only a portion of the array of individually controllable elements is used to generate the patterned radiation beam. Such a portion may be applied to generate a desired pattern on the substrate by scanning the substrate in a scan direction across the generated pattern of radiation spots, as illustrated, for example, in Figures 4 and 8. In this way, a step-and-scan approach may provide a desired pattern in a desired area on the substrate.

[0079]

[0091] It can be pointed out that such an approach, where only a portion of the array of controllable elements is used, does not necessarily result in a reduction in the pixel rate due to the exposure process: when only a portion of the array of controllable elements is used, the pattern rate, i.e. the rate at which the controllable elements are controlled, can be increased.

[0080]

[0092] In an embodiment of the second aspect of the present invention, there is provided a system for projecting a patterned radiation beam onto a substrate, the system configured to simultaneously project at least two two-dimensional patterns of radiation spots onto the substrate.

[0081]

[0093] In such an embodiment, the system, and in particular the microlens array of the system, may be configured to simultaneously project a first two-dimensional pattern of radiation spots and a second two-dimensional pattern of radiation spots onto the substrate, the patterns being spaced apart in the scan direction.

[0082]

[0094] In such an embodiment, two separate portions of the substrate can be scanned simultaneously to provide the desired pattern.

[0083]

[0095] In such an embodiment, a width of the first two-dimensional pattern in a direction perpendicular to the scanning direction may be selected to substantially correspond to a width of the second two-dimensional pattern in a direction perpendicular to the scanning direction, and a length of the first two-dimensional pattern in the scanning direction may substantially correspond to a length of the second two-dimensional pattern in the scanning direction.

[0084]

[0096] FIG. 9 shows diagrammatically such a radiation pattern that may be applied onto a substrate.

[0085]

[0097] 9 shows a schematic top view of a pattern of emissive dots 900 that may be generated using a system according to the invention, the pattern of emissive dots 900 comprising a first two-dimensional pattern of emissive dots 900.1 and a second two-dimensional pattern of emissive dots 900.2. Patterns 900.1 and 900.2 may, for example, have a length L in the Y direction and may be separated by a gap having a length G in the Y direction.

[0086]

[0098] Patterns 900.1 and 900.2 may comprise, for example, a plurality of rows of emitting dots, for example in the range of 50 to 200 rows, for example 100 rows. The gap length G may, for example, be equal to the length L or may be greater than L, for example a multiple of L. The gap length G may, for example, be twice the length L.

[0087]

[0099] 9 also shows diagrammatically a scan direction SD along which the substrate may be displaced across the pattern of radiation dots 900. By scanning the substrate across the pattern 900, an area of ​​the substrate may be exposed to a desired radiation pattern. In an embodiment, the radiation pattern 900 may comprise more than two two-dimensional patterns, for example five or more patterns. The total length Lt of the pattern 900 may span several cm, for example greater than 5 cm, and the width W of the pattern 900 may also span several cm, for example greater than 10 cm.

[0088]

[0100] According to a third aspect of the invention there is provided a method of controlling a radiation dose applied to a substrate. When a substrate is exposed to a pattern it may be advantageous to precisely control the radiation dose applied to a particular location, the radiation dose for example being capable of varying substantially continuously between zero and a maximum value. The method according to the third aspect of the invention utilises a modulated radiation beam and an array of individually controllable elements which can be imparted to the modulated radiation beam.

[0089]

[0101] In particular, the method comprises the following steps, which are illustrated in the flow chart of FIG.

[0090]

[0102] In a first step 1010, the method of controlling the radiation dose applied to the substrate comprises modulating a radiation beam according to a predetermined temporal profile, the profile comprising a plurality of different intensity levels of the radiation beam. In the sense of the present invention, modulating a radiation beam according to a predetermined temporal profile refers to modulating the intensity of the radiation beam according to a predetermined temporal profile or pattern. Such modulation may be repeated substantially continuously, i.e. the profile or pattern is repeated.

[0091]

[0103] In a second step 1020, the method according to the invention comprises imparting a modulated radiation beam by an array of individually controllable elements so as to generate a patterned modulated radiation beam by tilting the individually controllable elements between different positions about a tilt axis. In a second step 1020 of the method according to the invention, the modulated radiation beam is converted into a patterned modulated radiation beam, and the array of individually controllable elements is used to selectively deflect the modulated radiation beam towards the substrate or the projection system upon modulation according to a predetermined pattern over time. According to a third aspect of the invention, the step 1020 of imparting a modulated radiation beam by an array of controllable elements comprises determining a tilt sequence of one element of the array of controllable elements based on a radiation dose required for a particular part or location of the substrate and a predetermined profile over time, so as to expose the part of the substrate to a sequence of a plurality of different intensity levels. As will be explained in further detail subsequently, this allows a particular location on the substrate to be exposed with any desired combination of the different available intensity levels, thus allowing precise control of the radiation dose applied at that location.

[0092]

[0104] In a third step 1030, the method according to the invention comprises projecting the patterned modulated beam of radiation towards a substrate.

[0093]

[0105] In a fourth step 1040, the method comprises scanning the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, thereby exposing a portion of the substrate to the patterned modulated radiation beam. Because the portion of the substrate is exposed to a radiation beam that is modulated, i.e. has an intensity that varies according to a predetermined profile, and is delivered by the array of controllable elements, the radiation dose received by the portion can be precisely controlled.

[0094]

[0106] Thus, by suitable control of the elements imparting the modulated radiation beam, it is possible to control which portion of the modulated beam is actually applied onto the substrate. As mentioned above, the step of imparting a modulated radiation beam by an array of controllable elements involves a tilt sequence of one element of the array of controllable elements to expose a portion of the substrate to a sequence of different intensity levels. In doing so, the portion of the substrate will receive a sequence of different intensity levels available in the profile to which the radiation beam is modulated. As a result, the radiation dose, i.e. the integrated radiation to which the portion is exposed, can be controlled along a desired radiation dose. This can be explained as follows:

[0095]

[0107] 11 illustrates diagrammatically a profile or modulation profile 1100 that may be applied to a radiation beam. The diagrammatically illustrated profile 1100 comprises eight different intensity levels applied over a time period T. In the illustrated profile 1100, the highest intensity levels occur near the center of the profile and the lowest intensity levels are located at the edges of the profile. It has been observed that application of such an intensity profile allows for more precise control of the applied dose.

[0096]

[0108] When a radiation beam is modulated according to such a profile 1100 and a substrate is scanned across such a modulated radiation beam, a particular location on the substrate is exposed to an intensity that varies according to the profile shown.

[0097]

[0109] This is illustrated in Figure 12 which illustrates diagrammatically a radiation beam 1200 propagating along the Y or scan direction. Figure 12 illustrates diagrammatically the position of the radiation beam 1200 at three instants in time t1, t2, t3 during the scanning of a substrate across the radiation beam 1200, the radiation beam 1200 having a width Wb in the scan direction. In Figure 12, Y1 represents a particular location or portion of the substrate that is scanned or displaced under the radiation beam 1200. At t=t 1 , a location or portion Y 1 of the substrate is aligned with the front surface 1200 . 1 of the radiation beam 1200 . At t=t 2 , a location or portion Y 1 of the substrate is substantially aligned with the centre of the radiation beam 1200 . At t=t3, a location or portion Y1 of the substrate is aligned with the rear surface 1200.2 of the radiation beam 1200 and a further location Y2 on the substrate is aligned with the front surface of the radiation beam.

[0098]

[0110] If radiation beam 1100 is modulated according to the modulation pattern shown in FIG. 11, location Y1 will be exposed to a radiation dose that corresponds to the sum or integral of the pattern over time.

[0099]

[0111] The sum or integral of such modulated profile 1100 can be considered to correspond to the maximum radiation dose that can be applied to a particular portion or location on the substrate.

[0100]

[0112] If a lower radiation dose is required at a particular location, e.g. Y2, the method and system according to the third aspect of the present invention enables such a lower radiation dose to be achieved by providing a modulated radiation beam 1100 by an array of controllable elements and determining a tilt sequence of one element of the array of controllable elements to expose only a portion of the substrate to a series of multiple different intensity levels.

[0101]

[0113] For example, assume that location Y2 shown in Figure 12 requires only half the maximum radiation dose. To do so, the tilt sequence of controllable elements, e.g. mirrors, can be determined so that as location Y2 is scanned across the radiation beam 1100, it is struck by the radiation beam for only a selected portion of the period T. In other words, the controllable elements that apply the radiation beam to scan a particular location can be selectively brought to an "on" or "off" position, thereby exposing that particular location to only a range of available radiation or radiation levels, thus affecting the overall radiation dose applied at that location.

[0102]

[0114] Figures 13a and 13b show diagrammatically two examples of tilt sequences of controllable elements and the resulting applied radiation profiles.

[0103]

[0115] In the example of Figure 13a, the tilt sequence of the controllable elements impinging on the radiation beam is only in the "on" state when the intensity is at its highest value. During the remainder of the period T, the elements are in the "off" state and no radiation is projected onto the substrate. This results in an actual intensity profile 1300, which results in a radiation dose that is approximately half the radiation dose of profile 1100.

[0104]

[0116] 13b, the controllable element is in an “on” state during portions T1 and T2 of period T, and in an “off” state during the remaining portion of period T. This results in an actual intensity profile 1310, which again results in a radiation dose that is approximately half the radiation dose of profile 1100.

[0105]

[0117] As will be appreciated by those skilled in the art, by a suitable series of different intensity levels and tilting sequences of the controllable elements, precise control of the applied radiation dose at a particular location can be achieved. The method according to the third aspect of the invention can be considered as an example of so-called greyscaling. According to the invention, greyscaling is achieved both by modulating the intensity of the radiation beam and, during said modulation, by controlling the controllable elements to selectively apply the available radiation intensity.

[0106]

[0118] To ensure that each location on the substrate receives the desired radiation, it is also important to ensure that crosstalk between adjacent radiation spots is avoided as far as possible, whereby in the sense of the present invention crosstalk between radiation spots refers to radiation that is provided by a particular controllable element and focused by a particular lenslet of the microlens array towards a particular radiation spot but that partially influences the radiation levels at adjacent radiation spots.

[0107]

[0119] As will be appreciated, the occurrence of crosstalk makes it more difficult to control the actual radiation dose applied at a particular portion or location on the substrate.

[0108]

[0120] It has been observed that when applying conventional arrays of individually controllable elements, such as programmable mirror arrays, in combination with microlens arrays, undesirable levels of crosstalk may still occur. In order to further reduce the occurrence of such crosstalk, a system according to a fourth aspect of the invention may be applied. According to a fourth aspect of the invention, there is provided a system for projecting a patterned beam of radiation onto a substrate, the system comprising an array of individually controllable elements configured to impart a pattern to the beam of radiation by tilting the individually controllable elements between different positions about a tilt axis to generate the patterned beam of radiation.

[0109]

[0121] The system according to the invention further comprises a stage arrangement configured to hold the substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam. Such a stage arrangement may for example comprise one or more positioning devices for positioning the substrate relative to the patterned radiation beam. To do so, the stage arrangement may also comprise a position measurement system for providing measurement signals characterising the relative position of the patterned radiation beam and the substrate. The system according to the fourth aspect of the invention further comprises a projection system configured to receive the patterned radiation beam, the projection system comprising: A first microlens array; A second microlens array; and a pinhole array; and The first microlens array is configured to receive a patterned beam of radiation generated by the array of individually controllable elements and project the patterned beam of radiation onto the second microlens array, the second microlens array is configured to project the received patterned beam of radiation onto a substrate, and the pinhole array is disposed in an optical path of the patterned beam of radiation between the first and second microlens arrays. According to the invention, the pinhole array is configured to limit crosstalk between adjacent spots of radiation projected onto the substrate. By application of the second microlens array and the pinhole array, crosstalk between adjacent radiation spots can be substantially reduced.

[0110]

[0122] FIG. 14 shows diagrammatically a part of a projection system 1400 applicable in a system according to a fourth aspect of the invention.

[0111]

[0123] 14 shows a first microlens 1410 configured to receive a portion 1420 of a patterned radiation beam, the portion being generated, for example, by one controllable element of an array of controllable elements. The illustrated first microlens 1410 is configured to project the received portion 1420 of the radiation towards a second microlens 1430, which is configured to focus the received radiation, thereby forming a radiation spot 1440. The illustrated portion of the projection system 1400 further comprises a pinhole 1450, which is part of a pinhole array, the pinhole being configured to provide spatial filtering of the radiation emitted by the first microlens 1410. In the illustrated embodiment, the pinhole 1450 is positioned near a focal point 1460 of the first microlens 1410.

[0112]

[0124] The above-described system may be advantageously applied in a lithographic apparatus, especially a maskless lithographic apparatus.

[0113]

[0125] It may also be pointed out that the various aspects of the invention may be advantageously combined.

[0114]

[0126] In one embodiment, a controller is provided to control the individually addressable elements 102 and / or the patterning device 104. The controller may control the power of radiation emitted by one or more of the individually addressable elements. The controller may modulate the intensity of radiation emitted by one or more of the individually addressable elements. The controller may control / adjust the intensity uniformity across all or a portion of the array of individually addressable elements. The controller may adjust the radiation output of the individually addressable elements to correct imaging errors, such as etendue and optical aberrations (e.g. coma, astigmatism, etc.).

[0115]

[0127] In one embodiment, patterning the radiation may be performed by controlling the patterning device 104 so that the radiation delivered to certain areas of a resist layer on the substrate within a desired feature is of a sufficiently high intensity that those areas receive a radiation dose above the dose threshold during exposure, while other areas on the substrate receive a radiation dose below the dose threshold by providing zero or a significantly lower radiation intensity.

[0116]

[0128] In practice, the radiation dose at the edge of a desired feature will not change abruptly from a given maximum dose to zero dose, even if it is set to provide a maximum radiation intensity on one side of the feature boundary and a minimum radiation intensity on the other side. Instead, due to diffraction effects, the level of the radiation dose may drop across a transition zone. The location of the boundary of the desired feature that is ultimately formed after development of the resist is then determined by the location where the received dose falls below the radiation dose threshold. The profile of the radiation dose drop across the transition zone, and thus the exact location of the feature boundary, may be more precisely controlled by providing radiation to points on the substrate at or near the feature boundary, not only at maximum or minimum intensity levels, but also at intensity levels between the maximum and minimum intensity levels. This is commonly referred to as "grayscaling" or "gray leveling".

[0117]

[0129] Grayscaling may provide better control of the location of feature boundaries than is possible in lithography systems where the radiation intensity provided to the substrate can only be set to two values ​​(i.e., a maximum and a minimum). In an embodiment, at least three different radiation intensity values ​​may be projected, such as at least four radiation intensity values, at least eight radiation intensity values, at least 16 radiation intensity values, at least 32 radiation intensity values, at least 64 radiation intensity values, at least 100 radiation intensity values, at least 128 radiation intensity values, or at least 256 radiation intensity values. The method according to the third aspect of the invention may be considered as a method that allows such grayscaling. The grayscaling method according to the invention applies a plurality of different radiation intensity levels that may be selectively applied at specific locations by applying a tilt or deflection sequence of individually controllable elements of the patterning device. Grayscaling may also be performed by grouping a plurality of programmable elements and / or deflectors and controlling the number of elements and / or deflectors in a group that are switched on or off at a given time.

[0118]

[0130] In one example, the patterning device may have a set of states including (a) a black state, where the provided radiation has a minimal or even zero contribution to the intensity distribution of the corresponding pixel, (b) a whitest state, where the provided radiation has a maximal contribution, and (c) intermediate states, where the provided radiation has an intermediate contribution. These states are divided into a normal set used for normal beam patterning / printing and a compensation set used to compensate for the effects of defective elements. The normal set comprises a black state and a first group of intermediate states. This first group is described as gray states, which can be selected to provide an incremental contribution to the corresponding pixel intensity from a minimum black value up to a certain normal maximum value. The compensation set comprises the remaining second group of intermediate states together with a whitest state. This second group of intermediate states is described as white states, which can be selected to provide an incremental contribution to the corresponding pixel intensity from a minimum black value up to a certain normal maximum value corresponding to the whitest state. Although the second group of intermediate states is described as a white state, it will be understood that this is merely to facilitate distinguishing between normal and compensatory exposure steps, or alternatively, the entire plurality of states may be described as a sequence of gray states between black and white, selectable to enable grayscale printing.

[0119]

[0131] It should be understood that grayscaling may be used for additional or alternative purposes to those described above. For example, processing of a substrate after exposure may be adjusted such that there are more than two potential responses of regions of the substrate in response to the radiation dose level received. For example, portions of the substrate receiving a radiation dose below a first threshold respond in a first manner, portions of the substrate receiving a radiation dose above the first threshold but below a second threshold respond in a second manner, and portions of the substrate receiving a radiation dose above the second threshold respond in a third manner. Thus, grayscaling may be used to provide a radiation dose profile across the substrate having more than two desired dose levels. In an embodiment, the radiation dose profile has at least two desired dose levels, for example at least three desired radiation dose levels, at least four desired radiation dose levels, at least six desired radiation dose levels, or at least eight desired radiation dose levels.

[0120]

[0132] It should further be appreciated that the radiation dose profile may be controlled in ways other than simply by controlling the intensity of radiation received at each point as described above. For example, the radiation dose received by each point may alternatively or additionally be controlled by controlling the duration of exposure of that point. As a further example, each point may potentially be subjected to radiation in multiple successive exposures. Thus, the radiation dose received by each point may alternatively or additionally be controlled by exposing that point with a selected subset of the multiple successive exposures.

[0121]

[0133] Also, while the above discussion of grayscaling has focused on photolithography, similar concepts may be applied to the material deposition described herein, e.g., power levels and / or flow rates may be controlled to provide the grayscaling associated with material deposition.

[0122]

[0134] To form a pattern on a substrate, at each stage during the exposure process, it is necessary to set the patterning device to a requisite state. Therefore, control signals representative of the requisite states must be transmitted to the patterning device. Preferably, the lithographic apparatus includes a controller for generating the control signals. The pattern to be formed on the substrate may be provided to the lithographic apparatus in a vector-defined format, for example GDSII. To convert the design information into the control signals, the controller includes one or more data manipulation devices, each of which is configured to perform processing steps on a data stream representative of the pattern. The data manipulation devices may collectively be referred to as a "data path".

[0123]

[0135] The data manipulation devices of the data path may be configured to perform one or more of the following functions: converting vector-based design information into bitmap pattern data (and then into a required radiation dose map (i.e., a required radiation dose profile across the substrate)) or into a required radiation dose map, converting the required radiation dose map into a required radiation intensity value for each individually addressable element, and converting the required radiation intensity value for each individually addressable element into a corresponding control signal.

[0124]

[0136] In one embodiment, control signals may be provided to the individually addressable elements 102 and / or one or more other devices (e.g., sensors) by wired or wireless communication. Also, signals from the individually addressable elements 102 and / or from one or more other devices (e.g., sensors) may be communicated to the controller. As with the control signals, power may be provided to the individually addressable elements 102 and / or one or more other devices (e.g., sensors) by wired or wireless means. For example, in a wired embodiment, power may be provided by one or more wires, whether the same or different as those carrying the signals. A sliding contact arrangement may be provided to transmit the power. In a wireless embodiment, power may be delivered by RF coupling.

[0125]

[0137] While the above discussion has focused on control signals provided to the individually addressable elements 102 and / or one or more other devices (e.g., deflectors and / or sensors), these should be understood to additionally or alternatively include the transmission of signals from the individually addressable elements 102 and / or from one or more other devices (e.g., sensors) to a controller through suitable configurations. Thus, communication may be unidirectional (e.g., only to or from the individually addressable elements 102 and / or one or more other devices (e.g., sensors)) or bidirectional (i.e., from the individually addressable elements 102 and / or one or more other devices (e.g., sensors) and to the individually addressable elements 102 and / or one or more other devices (e.g., sensors)).

[0126]

[0138] In one embodiment, the control signals for providing the pattern may be modified to account for factors that may affect the proper delivery and / or realization of the pattern on the substrate. For example, a correction may be applied to the control signals to account for heating of one or more of the individually addressable elements 102, lenses, etc. Such heating may cause changes in pointing directions of the individually addressable elements 102, lenses, etc., changes in radiation uniformity, etc. In one embodiment, measured temperature and / or expansion / contraction associated with the individually addressable elements 102 and / or other elements, for example from a sensor, may be used to modify the control signals that would otherwise be provided to form the pattern. Thus, for example, during exposure, the temperature of the individually addressable elements 102 may vary, which variation causes changes in the projected pattern that would have been provided at a single constant temperature. Thus, the control signals may be modified to account for such variations. Similarly, in one embodiment, results from an alignment sensor and / or a level sensor 150 may be used to modify the pattern provided by the individually addressable elements 102. The pattern may be altered to correct, for example, distortions that may be caused by optical components (if any) between the individually addressable elements 102 and the substrate 114, irregularities in the positioning of the substrate 114, non-uniformities in the substrate 114, and the like.

[0127]

[0139] In one embodiment, the change in the control signal may be determined based on a theory of the physical / optical consequences of the desired pattern caused by the measured parameters (e.g., the measured temperature, the distance measured by a level sensor, etc.). In one embodiment, the change in the control signal may be determined based on an experimental or empirical model of the physical / optical consequences of the desired pattern caused by the measured parameters. In one embodiment, the change in the control signal may be applied in a feedforward and / or feedback manner.

[0128]

[0140] In an embodiment, the lithographic apparatus may include a sensor 118 for measuring a property of the radiation that is or is to be transmitted towards the substrate by one or more individually addressable elements 102. Such a sensor may be a spot sensor or a transmission image sensor. The sensor may be used to determine, for example, the intensity of the radiation from the individually addressable elements 102, the uniformity of the radiation from the individually addressable elements 102, the cross-sectional size or area of ​​the spot of radiation from the individually addressable elements 102, and / or the location (in the XY plane) of the spot of radiation from the individually addressable elements 102.

[0129]

[0141] Although specific reference may be made in the present text to the use of the lithographic apparatus in the manufacture of a particular device or structure (e.g., an integrated circuit or a flat panel display), it should be understood that the lithographic apparatus and lithographic methods described herein may have other applications, including but not limited to the manufacture of integrated circuits, integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, LCDs, OLED displays, thin film magnetic heads, microelectromechanical devices (MEMS), micro-optical-electromechanical systems (MOEMS), DNA chips, packaging (e.g., flip chips, rewiring, etc.), flexible displays or electronics (displays or electronics that may be rollable and foldable like paper and remain non-deformable, conformable, contoured, thin, and / or lightweight, e.g., flexible plastic displays), etc. Also, for example, in flat panel displays, the apparatus and methods of the present invention may be used to assist in the production of various layers, e.g., thin film transistor layers and / or color filter layers. Thus, variations of the apparatus herein may be used in the manufacture of a variety of electronic and other devices or patterns, including on flexible substrates such as, for example, plastic or metal foils, using, for example, roll-to-roll techniques and / or foils on glass carriers.

[0130]

[0142] In the context of such alternative applications, those skilled in the art will recognize that use of the terms "wafer" or "die" herein may be considered synonymous with the more general terms "substrate" or "target portion", respectively. A substrate as referred to herein may be processed, before or after exposure, in, for example, a track (e.g., a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure herein may be applied to these and other substrate processing tools. Furthermore, a substrate may be processed multiple times, for example to produce a multi-layer IC, and thus the term substrate as used herein may also refer to a substrate that already includes multiple processed layers.

[0131]

[0143] A flat panel display substrate may be rectangular in shape. A lithographic apparatus designed to expose this type of substrate may provide an exposure area that covers the entire width of the rectangular substrate or a portion of the width (e.g., half the width). The substrate may be scanned under the exposure area while the patterning device synchronously provides a patterned beam. In this manner, all or part of the desired pattern is transferred to the substrate. If the exposure area covers the entire width of the substrate, exposure may be completed in a single scan. If the exposure area covers, for example, half the width of the substrate, the substrate may be moved in the short direction after the first scan, and further scans are typically performed to expose the remainder of the substrate.

[0132]

[0144] The term "patterning device" as used herein should be interpreted broadly as referring to any device that can be used to modulate the cross-section of a radiation beam, such as to generate a pattern on (a part of) a substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to a desired pattern in a target portion of the substrate, for example if the pattern comprises phase-shifting features or so-called assist features. Similarly, the pattern ultimately generated on the substrate may not correspond to the pattern formed at any instant in time by the array of individually addressable elements. This will be the case in arrangements where the final pattern formed in each portion of the substrate is built up over a given time period or a given number of exposures, where the pattern provided by the array of individually addressable elements and / or the relative position of the substrate varies. Typically, the pattern generated in the target portion of the substrate will correspond to a particular functional layer of a device being generated in the target portion, for example an integrated circuit or a flat panel display (for example a color filter layer of a flat panel display or a thin film transistor layer of a flat panel display). Examples of such patterning devices include, for example, reticles, programmable mirror arrays, laser diode arrays, light emitting diode arrays, grating light valves, and LCD arrays. Patterning devices comprising a plurality of programmable elements, each capable of modulating the intensity of a portion of the radiation beam (e.g. all devices other than the reticles mentioned in the previous sentence) are collectively referred to herein as "contrast devices", including patterning devices in which the pattern is programmable with the aid of electronics (such as a computer), e.g. electronically programmable patterning devices having a plurality of programmable elements that impart a pattern to the radiation beam by modulating the phase of a portion of the radiation beam relative to adjacent portions of the radiation beam. In one embodiment, the patterning device comprises at least 10 programmable elements, e.g. at least 100, at least 1000, at least 10000, at least 100000, at least 1 million, or at least 10 million,Some embodiments of these devices are described in more detail below.

[0133]

[0145] Programmable mirror arrays. A programmable mirror array may comprise a matrix-addressable surface having a viscoelastic control layer and a reflective surface. The basic principle behind such devices is that, for example, addressed areas of the reflective surface reflect incident radiation as diffracted radiation, while unaddressed areas reflect incident radiation as undiffracted radiation. Using an appropriate spatial filter, the undiffracted radiation can be filtered out of the reflected beam, leaving only the diffracted radiation to reach the substrate. In this way the beam becomes patterned according to the addressing pattern of the matrix-addressable surface. Alternatively, the filter may filter out the diffracted radiation, leaving only the undiffracted radiation to reach the substrate. Arrays of diffractive optical MEMS devices may be correspondingly used. The diffractive optical MEMS device may comprise a number of reflective ribbons that can be deformed relative to one another to form a diffraction grating that reflects incident radiation as diffracted radiation. A further embodiment of a programmable mirror array employs a matrix arrangement of tiny mirrors, each of which can be individually tilted about an axis by application of a suitable localized electric field or by using piezoelectric actuation means. The degree of tilt defines the state of each mirror. The mirrors are controllable by suitable control signals from a controller when the elements are not faulty. Each non-faulty element is controllable to adopt any one of a set of states so as to adjust the intensity of a corresponding pixel in the projected radiation pattern. Again, the mirrors are matrix-addressable, so that addressed mirrors will reflect an incoming radiation beam in a different direction than unaddressed mirrors. In this manner, the reflected beam may be patterned according to an addressing pattern of the matrix-addressable mirrors. The required matrix addressing may be performed using suitable electronic means. Further information on the mirror arrays referred to herein can be gleaned from, for example, U.S. Pat. Nos. 5,296,891 and 5,523,193, and PCT Patent Application Publication Nos. 98 / 38597 and 98 / 33096, which are incorporated herein by reference in their entireties.

[0134]

[0146] A programmable LCD array. One example of such a construction is described in U.S. Patent No. 5,229,872, which is incorporated herein by reference in its entirety.

[0135]

[0147] A lithographic apparatus may comprise one or more patterning devices, e.g. one or more contrast devices. For example it may comprise a number of arrays of individually addressable elements, each of which is controlled independently of each other. In such an arrangement, some or all of the arrays of individually addressable elements may have at least one of a common illumination system (or part of an illumination system), a common support structure for the arrays of individually addressable elements, and / or a common projection system (or part of a projection system).

[0136]

[0148] For example, when pre-biasing of features, optical proximity correction features, phase variation techniques, and / or multiple exposure techniques are used, the pattern "displayed" on the array of individually addressable elements may be substantially different from the pattern that is ultimately transferred to a layer of or on the substrate. Similarly, the pattern that is ultimately generated on the substrate may not correspond to the pattern formed on the array of individually addressable elements at any instant in time. This may be the case in arrangements where the final pattern formed on portions of the substrate is built up over a given period of time or a given number of exposures, where the pattern on the array of individually addressable elements and / or the relative position of the substrate varies.

[0137]

[0149] The projection system and / or illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, to direct, shape or control the beam of radiation.

[0138]

[0150] The lithographic apparatus may be of a type having two (e.g. dual stage) or more substrate tables (and / or two or more patterning device tables), or one or more substrate tables in combination with another table that does not hold a substrate (e.g. a table for cleaning and / or measurement, etc.) In such a "multi-stage" machine, the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.

[0139]

[0151] The lithographic apparatus may be of a type in which at least a part of the substrate may be covered with an "immersion liquid" having a relatively high refractive index, such as water, so as to fill a space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, for example between the patterning device and the projection system. Immersion techniques are used to increase the NA of projection systems. The term "immersion" as used herein does not mean that a structure such as the substrate must be submerged in liquid, but rather that a liquid is located between the projection system and the substrate during exposure.

[0140]

[0152] The apparatus may also be provided with a fluid processing cell to allow interaction of a fluid with the irradiated portion of the substrate (e.g., to selectively attach chemicals to the substrate or to selectively modify the surface structure of the substrate).

[0141]

[0153] In one embodiment, the substrate has a substantially circular shape, optionally with a notch and / or flattened edge along a portion of its periphery. In one embodiment, the substrate has a polygonal shape, for example a rectangular shape. Embodiments in which the substrate has a substantially circular shape include those in which the substrate has a diameter of at least 25 mm, for example at least 50 mm, at least 75 mm, at least 100 mm, at least 125 mm, at least 150 mm, at least 175 mm, at least 200 mm, at least 250 mm, or at least 300 mm. In one embodiment, the substrate has a diameter of at most 500 mm, at most 400 mm, at most 350 mm, at most 300 mm, at most 250 mm, at most 200 mm, at most 150 mm, at most 100 mm, or at most 75 mm. Embodiments in which the substrate is polygonal, e.g. rectangular, include those in which at least one side of the substrate, e.g. at least two sides or at least three sides, have a length of at least 5 cm, e.g. at least 25 cm, at least 50 cm, at least 100 cm, at least 150 cm, at least 200 cm, or at least 250 cm. In one embodiment, at least one side of the substrate has a length of at most 1000 cm, e.g. at most 750 cm, at most 500 cm, at most 350 cm, at most 250 cm, at most 150 cm, or at most 75 cm. In one embodiment, the substrate is a rectangular substrate having a length of about 250-350 cm and a width of about 250-300 cm. The thickness of the substrate may vary and may depend, to an extent, on, e.g., the substrate material and / or the substrate dimensions. In one embodiment, the thickness is at least 50 μm, such as at least 100 μm, at least 200 μm, at least 300 μm, at least 400 μm, at least 500 μm, or at least 600 μm. In an embodiment, the thickness of the substrate is at most 5000 μm, such as at most 3500 μm, at most 2500 μm, at most 1750 μm, at most 1250 μm, at most 1000 μm, at most 800 μm, at most 600 μm, at most 500 μm, at most 400 μm, or at most 300 μm. Substrates referred to herein may be processed before or after exposure, for example in a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist).Properties of the substrate may be measured before or after exposure, for example with a metrology tool and / or an inspection tool.

[0142]

[0154] In one embodiment, the substrate is provided with a resist layer. In one embodiment, the substrate is a wafer, for example a semiconductor wafer. In one embodiment, the wafer material is selected from the group consisting of Si, SiGe, SiGeC, SiC, Ge, GaAs, InP, and InAs. In one embodiment, the wafer is a III / V compound semiconductor wafer. In one embodiment, the wafer is a silicon wafer. In one embodiment, the substrate is a ceramic substrate. In one embodiment, the substrate is a glass substrate. Glass substrates may be useful, for example, in the manufacture of flat panel displays and liquid crystal display panels. In one embodiment, the substrate is a plastic substrate. In one embodiment, the substrate is transparent (to the naked human eye). In one embodiment, the substrate is colored. In one embodiment, the substrate is colorless. In one embodiment, the substrate comprises a plastic foil on a temporary glass carrier. This may involve a coating layer such as polyimide on a glass substrate that is processed in a similar manner as a glass display, but the glass is removed after processing, for example with a UV laser step, and preferably after laminating the remaining foil with a protective plastic for increased robustness and ease of handling.

[0143]

[0155] Although the patterning device 104 is described and / or illustrated in one embodiment as being above the substrate 114, it may alternatively or additionally be located below the substrate 114. Also, in one embodiment, the patterning device 104 and the substrate 114 may be adjacent, e.g., the patterning device 104 and the substrate 114 extend vertically and the pattern is projected horizontally. In one embodiment, the patterning device 104 is provided to expose at least two opposing sides of the substrate 114. For example, there may be at least two patterning devices 104 on each of at least opposing sides of the substrate 114 to expose those sides. In one embodiment, there may be a single patterning device 104 for projecting one side of the substrate 114 and appropriate optical components (e.g., beam directing mirrors) for projecting the pattern from the single patterning device 104 onto another side of the substrate 114.

[0144]

[0156] Embodiments may also be described using the following clauses. 1. A method of exposing a substrate to a patterned beam of radiation, comprising the steps of: Providing a beam of radiation; imparting a radiation beam with an array of individually controllable elements; and generating a patterned beam of radiation from the beam of radiation by tilting the individually controllable elements between different positions about a tilt axis; projecting a patterned beam of radiation towards a substrate; scanning the substrate in the scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, with tilt axes of the individually controllable elements being substantially perpendicular to the scan direction; A method comprising: 2. The method of claim 1, wherein variation in the tilt angle of one controllable element of the array of individually controllable elements causes only a positional variation in the scan direction of a portion of the patterned radiation beam imparted by the control element and projected towards the substrate. 3. The system of clause 2, wherein the individually controllable elements can be positioned in an on position that causes a portion of the radiation beam provided by the element to be projected towards the substrate, and an off position that causes a portion of the radiation beam provided by the element to be projected away from the substrate. 4. The method of claim 3, wherein a variation in the tilt angle of one controllable element of the array of individually controllable elements in the on position causes some positional variation. 5. A system for projecting a patterned beam of radiation onto a substrate, comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a stage device configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; A system wherein the tilt axes of the individually controllable elements are substantially perpendicular to the scan direction. 6. The system of clause 5, wherein variation in the tilt angle of one controllable element of the array of individually controllable elements causes only positional variation in the scan direction of a portion of the patterned radiation beam imparted by the controllable element and projected towards the substrate. 7. The system of clause 5 or 6, wherein the array of individually controllable elements comprises a programmable mirror array, such as a 2D tilting mirror array. 8. A lithographic apparatus comprising a system according to any of clauses 5 to 7. 9. A lithographic apparatus according to clause 8, further comprising a radiation source configured to provide a radiation beam. 10. A system for projecting a patterned beam of radiation onto a substrate, comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a stage device configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; a projection system comprising a microlens array, The microlens array is configured to project a first two-dimensional pattern of radiation spots and a second two-dimensional pattern of radiation spots onto a substrate; a width of the first two-dimensional pattern in a direction perpendicular to the scanning direction substantially corresponds to a width of the second two-dimensional pattern in a direction perpendicular to the scanning direction; A system, wherein a length of the first two-dimensional pattern in the scanning direction substantially corresponds to a length of the second two-dimensional pattern in the scanning direction, and the first two-dimensional pattern and the second two-dimensional pattern are spaced apart from each other in the scanning direction. 11. The system of claim 10, wherein the individually controllable elements can be positioned in an on position that causes a portion of the radiation beam provided by the element to be projected towards the substrate, and an off position that causes a portion of the radiation beam provided by the element to be projected away from the substrate. 12. The system described in clause 11, wherein the array of individually controllable elements comprises a first position configured to generate a first two-dimensional pattern of radiation spots and a second position configured to generate a second two-dimensional pattern of radiation spots. 13. A lithographic apparatus comprising a system according to any of clauses 10 to 12. 14. A method of controlling a radiation dose applied to a substrate, comprising: modulating the radiation beam according to a predetermined profile over time, the profile comprising a plurality of different intensity levels of the radiation beam; imparting a modulated radiation beam by the array of individually controllable elements to generate a patterned modulated radiation beam by tilting the individually controllable elements between different positions about a tilt axis; and projecting a patterned modulated beam of radiation towards a substrate; scanning the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, thereby exposing a portion of the substrate to the patterned modulated radiation beam; The step of imparting a modulated radiation beam includes: 1. A method comprising: determining a tilt sequence of an element of an array of controllable elements based on a required radiation dose of a portion of a substrate and a predetermined profile over time to expose the portion of a substrate to a series of a plurality of different intensity levels. 15. The method of claim 14, wherein the sum of a series of a plurality of different intensity levels to which a portion is exposed corresponds substantially to a required radiation dose. 16. The method of claim 14 or 15, wherein the plurality of different intensity levels of the predetermined profile are arranged to have a relatively high intensity level at or near the centre of the predetermined profile. 17. A system for projecting a patterned beam of radiation onto a substrate, comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a radiation beam modulator configured to modulate a radiation beam according to a predetermined profile over time, the profile comprising a plurality of different intensity levels of the radiation beam; the array of individually controllable elements is configured to impart a modulated radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned modulated radiation beam; The system further comprises: a stage device configured to hold a substrate and configured to expose the substrate to the patterned radiation beam, thereby scanning the substrate in a scan direction across the patterned modulated radiation beam to expose a portion of the substrate to the patterned modulated radiation beam; a control unit configured to determine a tilt sequence of an element of the array of controllable elements based on a required radiation dose of the portion of the substrate and a predetermined profile over time to expose the portion of the substrate to a sequence of a plurality of different intensity levels; A system comprising: 18. A lithographic apparatus comprising a system according to clause 17. 19. A system for projecting a patterned beam of radiation onto a substrate, comprising: an array of individually controllable elements configured to impart to the radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a stage device configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; a projection system configured to receive the patterned beam of radiation; The projection system is A first microlens array; A second microlens array; and a pinhole array; and a first microlens array configured to receive a patterned radiation beam and project the patterned radiation beam onto a second microlens array, the second microlens array configured to project the received patterned radiation beam onto a substrate; and a pinhole array disposed in an optical path of the patterned radiation beam between the first microlens array and the second microlens array, the pinhole array configured to limit crosstalk between adjacent radiation spots projected onto the substrate.

[0145]

[0157] In the present description, the term "lens" should be generally understood to encompass any refractive, reflective, and / or diffractive optical element that provides the same function as the referenced lens. For example, an imaging lens may be embodied in the form of a conventional diffractive lens with optical power, a Schwarzschild reflective system with optical power, and / or a zone plate with optical power. An imaging lens may also comprise non-imaging optics, provided that the resulting effect is to produce a focused beam of light.

[0146]

[0158] Although specific embodiments have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, an embodiment of the invention may take the form of a computer program comprising one or more sequences of machine-readable instructions describing the method as disclosed above, or a data storage medium having stored thereon such a computer program (e.g., a semiconductor memory, a magnetic or optical disk).

[0147]

[0159] Also, while specific embodiments and examples have been described, those skilled in the art will understand that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses of the present invention, as well as obvious modifications and equivalents thereof. And, while several variations of the present invention have been shown and described in detail, other modifications that are within the scope of the present invention will be readily apparent to those skilled in the art based on this disclosure. For example, it is contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the present invention. Thus, it should be understood that various features and aspects of the disclosed embodiments may be combined with or substituted for one another to form varying modes of the disclosed invention. In one embodiment, one or more features or aspects disclosed in U.S. Patent Application Publication No. 2011-0188016 and PCT Patent Application Publication No. 2010 / 032224 may be combined with or substituted for one or more features or aspects disclosed herein, the entire contents of which are incorporated herein by reference.

Claims

1. 1. A method of exposing a substrate to a patterned beam of radiation, comprising the steps of: Providing a beam of radiation; imparting said radiation beam with an array of individually controllable elements; and generating a patterned beam of radiation from the beam of radiation by tilting the individually controllable elements between different positions about a tilt axis; and projecting the patterned beam of radiation towards a substrate; scanning the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, with the tilt axes of the individually controllable elements being substantially perpendicular to a scan direction; the individually controllable elements are rectangular mirrors arranged along a direction different from the scanning direction; The tilt axis is oriented along a diagonal of the mirror.

2. 2. The method of claim 1 , wherein variation in the tilt angle of one individually controllable element of the array causes only a positional variation in the scan direction of a portion of the patterned radiation beam imparted by the individually controllable element and projected towards the substrate.

3. 3. The method of claim 2, wherein the individually controllable elements can be positioned in an on position that causes a portion of the radiation beam provided by the individually controllable elements to be projected towards the substrate, and an off position that causes the portion of the radiation beam provided by the individually controllable elements to be projected away from the substrate.

4. The method of claim 3 , wherein a variation in a tilt angle of one of the individually controllable elements of the array in the on position causes a positional variation of the portion.

5. 10. The method of claim 1 , further comprising controlling a radiation dose applied to the substrate, modulating the radiation beam according to a predetermined profile over time, the profile comprising a plurality of different intensity levels of the radiation beam; imparting a modulated radiation beam by the array to generate the patterned modulated radiation beam by tilting the individually controllable elements between different positions about the tilt axis; and projecting the patterned modulated beam of radiation towards the substrate; scanning the substrate in the scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam, thereby exposing a portion of the substrate to the patterned modulated radiation beam; The step of imparting to the modulated radiation beam comprises: determining a tilt sequence of one of the individually controllable elements of the array based on a radiation dose required for the portion of the substrate and the predetermined profile over time to expose the portion of the substrate to a series of the plurality of different intensity levels.

6. The method of claim 5 , wherein a sum of the series of the plurality of different intensity levels to which the portion is exposed corresponds substantially to the required radiation dose.

7. 7. The method of claim 5 or 6, wherein the plurality of different intensity levels of the predetermined time-course profile are arranged to have a relatively high intensity level at or near the centre of the predetermined time-course profile.

8. 1. A system for projecting a patterned beam of radiation onto a substrate, comprising: an array of individually controllable elements configured to impart to a radiation beam by tilting the individually controllable elements between different positions about a tilt axis to generate a patterned radiation beam; and a stage device configured to hold a substrate and configured to scan the substrate in a scan direction across the patterned radiation beam to expose the substrate to the patterned radiation beam; the tilt axes of the individually controllable elements are substantially perpendicular to the scan direction; the individually controllable elements are rectangular mirrors arranged along a direction different from the scanning direction; wherein the tilt axis is oriented along a diagonal of the mirror.

9. 9. The system of claim 8, wherein variation in the tilt angle of one individually controllable element of the array causes only a positional variation in the scan direction of a portion of the patterned radiation beam imparted by the individually controllable element and projected towards the substrate.

10. 10. A system according to claim 8 or 9, wherein the array comprises a programmable mirror array, such as a 2D tilting mirror array.

11. 9. The system of claim 8, a radiation beam modulator configured to modulate the radiation beam according to a predetermined profile over time, the profile comprising a plurality of different intensity levels of the radiation beam; the array is configured to impart to the modulated radiation beam by tilting the individually controllable elements between different positions about the tilt axis to generate a patterned modulated radiation beam; The system further comprises: a stage device configured to hold a substrate and configured to expose the substrate to the patterned radiation beam and to scan the substrate in the scan direction across the patterned modulated radiation beam to thereby expose a portion of the substrate to the patterned modulated radiation beam; a control unit configured to determine a tilt sequence of the one of the individually controllable elements of the array based on a required radiation dose of the portion of the substrate and the predetermined profile over time to expose the portion of the substrate to a sequence of the plurality of different intensity levels; A system comprising:

12. A lithographic apparatus comprising a system according to any one of claims 8 to 11.

13. The lithographic apparatus of claim 12, further comprising a radiation source configured to provide the radiation beam.

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