Patent Application
20070228295
The present invention relates to a lithographic apparatus, a support constructed to support a patterning device, and a method for manufacturing a device.
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
In any lithographic apparatus, the mask or reticle needs to be placed at a required position with respect to the radiation beam.
The patterning device is supported by a support which can be moved in order to place said device at the required position. The position of the patterning device on a support is well-defined with respect to the support and needs said position to be fixed with respect to the support when the support is being moved. The fixation of the patterning device is usually accomplished by applying a vacuum force on at least part of the patterning device so that it is sucked against the support.
In order to enhance the throughput of such a lithographic apparatus, the patterning device is subjected to increasing accelerations, resulting in a need for increased forces required to keep the patterning device fixed at its required position. In this context accelerations may be either positive or negative. In particular in the so-called scanners, the patterning device moves rapidly while the radiation beam remains stationary and the patterning device imparts the radiation beam with a pattern in its cross-section.
It is desirable to provide a lithographic apparatus which allows for a high throughput whilst maintaining high accuracy of the intended localization of the pattern as forced upon the radiation beam. This results in a good overlay, that is a high level of correspondence between the intended position of the pattern as transferred onto a target position on a substrate and the actual position of the pattern as transferred onto that target portion of the substrate.
It is further desirable to provide a support constructed to support a patterning device and allowing for accurately projecting the pattern onto a predetermined surface using a radiation beam, even when the support is or has been subjected to a high acceleration.
It is desirable to provide a method comprising supporting a patterning device using a support that allows for accurately projecting the pattern onto a substrate even when the support is subjected or has been subjected to a high acceleration.
It is further desirable to provide a device manufacturing method comprising transferring a pattern from a patterning device onto a substrate even when the patterning device is subjected or has been subjected to a high acceleration.
According to an aspect of the invention, there is provided a support constructed to support a patterning device which patterning device is capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam, wherein the support is arranged to subject, at least when the support is accelerated, a first side of the patterning device to at least one first force normal to the direction of the acceleration so that an acceleration of the patterning device with respect to the support is counteracted by frictional forces occurring at a contact area between the patterning device and the support, wherein the support is associated with a clamping device which is arranged to subject a second side of the patterning device to at least one second force normal to the direction of the acceleration of the support, at least when the support is accelerated
According to an aspect of the invention, there is provided that a device manufacturing method comprising transferring a pattern from a patterning device onto a substrate, wherein the method comprises supporting the patterning device using a support; accelerating the support, subjecting a first side of the patterning device to at least one first force normal to the direction of the acceleration so that an acceleration of the patterning device with respect to the support is suppressed by frictional forces occurring at a contact area between the patterning device and the support; and
subjecting a second side of the patterning device to at least one second force normal to the direction of the acceleration of the support, at least when the support is accelerated.
According to an aspect of the invention, there is provided a method comprising supporting a patterning device using a support; accelerating the support; subjecting a first side of the patterning device to a first force normal to the direction of the acceleration so that an acceleration of the patterning device with respect to the support is counteracted by frictional forces occurring at a contact area between the patterning device and the support; and
subjecting a second side of the patterning device to a second force normal to the direction of the acceleration of the support, at least when the support is accelerated.
According to an aspect of the invention, there is provided a lithographic apparatus comprising an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; wherein the support is arranged, to subject at least when the support is accelerated, a first side of the patterning device to at least one first force normal to the direction of the acceleration so that an acceleration of the patterning device with respect to the support is counteracted by frictional forces occurring at a contact area between the patterning device and the support, wherein the support is associated with a clamping device which is arranged to subject a second side of the patterning device to at least one second force normal to the direction of the acceleration of the support, at least when the support is accelerated.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
In the drawings like-parts have like-references.
The 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, for directing, shaping, or controlling radiation.
The support structure supports, i.e. bears the weight of, the patterning device. It holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which is movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”
The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.
The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.
The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.
As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).
The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more mask tables). In such “multiple stage” machines 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.
The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.
Referring to
The illuminator IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. 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 can be adjusted. In addition, the illuminator IL may comprise various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.
The radiation beam B is incident on the patterning device (e.g., mask MA), which is held on the support structure (e.g., mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in
The depicted apparatus could be used in at least one of the following modes:
Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.
All the
The support MT is associated with a clamping device CD (as shown in
In the embodiment shown in
In contrast to the passive embodiment shown in
In the embodiment shown in
Although in the embodiments shown the first and second side S1, S2 of the patterning device are substantially parallel to each other it is possible the sides are non-parallel as well.
In the reverse case the support MT undergoes a reverse acceleration (deceleration) DCmt. Again a counter force acts on the respective masses M1 and M2 and now provides, via pivoting parts PP, for M2 an additional clamping force FA2, which is now (contrary to the illustrated case) oriented in the direction of the support MT.
As shown in
It will be clear that the invention aims to maintain the position of the patterning device MA with respect to the support MT, not only when a positive acceleration of the support occurs, but equally when a negative acceleration, i.e. a deceleration of the support occurs.
It should further be borne in mind that although in all the embodiments shown the patterning device is oriented substantially horizontally, the invention is by no means limited to such an orientation of the patterning device. It is also possible that the beam is vertically or diagonally oriented and that as a consequence thereof or because of any reason the patterning device is oriented vertically or diagonally.
Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.
Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.
The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.
The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.
While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.
The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NL04/00907 | 12/23/2004 | WO | 12/7/2006 |
