Patent Grant
7414699
The present invention relates to a lithographic apparatus 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.
It has been proposed to immerse the substrate in the lithographic projection apparatus in a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the final element of the projection system and the substrate. The point of this is to enable imaging of smaller features since the exposure radiation will have a shorter wavelength in the liquid. (The effect of the liquid may also be regarded as increasing the effective NA of the system and also increasing the depth of focus.) Other immersion liquids have been proposed, including water with solid particles (e.g. quartz) suspended therein.
However, submersing the substrate or substrate and substrate table in a bath of liquid (see, for example, U.S. Pat. No. 4,509,852, hereby incorporated in its entirety by reference) means that there is a large body of liquid that must be accelerated during a scanning exposure. This requires additional or more powerful motors and turbulence in the liquid may lead to undesirable and unpredictable effects.
One of the solutions proposed is for a liquid supply system to provide liquid on only a localized area of the substrate and in between the final element of the projection system and the substrate using a liquid confinement system (the substrate generally has a larger surface area than the final element of the projection system). One way which has been proposed to arrange for this is disclosed in PCT patent application WO 99/49504, hereby incorporated in its entirety by reference. As illustrated in
In a lithographic apparatus that confines immersion liquid, such as water, to only a localized area between the projection system and the substrate, problems may be caused by any liquid left behind on the substrate after the projection system and liquid supply system have passed (from the point of view of the substrate). For example, liquid left on the substrate surface may evaporate causing localized cooling of the substrate which can lead to thermal distortion of the substrate. Humid gas resulting from such evaporation may affect the results of interferometric displacement measuring systems commonly used to monitor the position of the substrate table.
Accordingly, it would be advantageous, for example, to provide an approach to removal of residual liquid from the substrate in an immersion lithography apparatus.
According to an aspect of the invention, there is provided a lithographic projection apparatus arranged to project a pattern from a patterning device onto a substrate through a liquid provided in a space adjacent the substrate, the apparatus comprising an ultrasonic transducer configured to emit an ultrasonic beam toward the substrate to atomize liquid theron.
According to an aspect of the invention, there is provided a lithographic projection apparatus, comprising:
an illuminator configured to condition a radiation beam;
a support constructed to hold a patterning device, the patterning device configured to impart the radiation beam with a pattern in its cross-section to form a patterned radiation beam;
a substrate table constructed to hold a substrate;
a projection system configured to project the patterned radiation beam onto a target portion of the substrate;
a liquid supply system configured to at least partly fill a space between the projection system and the substrate with a liquid, the liquid supply system providing the liquid onto the substrate; and
an ultrasonic transducer configured to emit an ultrasonic beam toward the substrate to atomize liquid thereon.
According to an aspect of the invention, there is provided a device manufacturing method, comprising:
projecting a patterned beam of radiation onto a substrate through a liquid provided in a space adjacent the substrate; and
projecting an ultrasonic beam toward the substrate to atomize liquid thereon.
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:
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 may be fixed or 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.
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 PB 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 PB passes through the projection system PL, 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 PB. 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.
A further immersion lithography solution with a localized liquid supply system is shown in
Another immersion lithography solution with a localized liquid supply system solution which has been proposed is to provide the liquid supply system with a liquid confinement structure which extends along at least a part of a boundary of the space between the final element of the projection system and the substrate table. Such a system is shown in
The liquid is confined in the reservoir by a gas seal 16 between the bottom of the liquid confinement structure 12 and the surface of the substrate W. The gas seal is formed by gas, e.g. air, synthetic air, N2 or an inert gas, provided under pressure via inlet 15 to the gap between liquid confinement structure 12 and substrate and extracted via first outlet 14. The overpressure on the gas inlet 15, vacuum level on the first outlet 14 and geometry of the gap are arranged so that there is a high-velocity gas flow inwards that confines the liquid. It will be understood by the person skilled in the art that other types of seal could be used to contain the liquid.
Since it is typically difficult to make the seal device perfectly effective, it is likely that a thin film of liquid 11a, perhaps of the order of 10 μm thick, will be left behind as the substrate moves (e.g., scans) in the direction of the arrow S. (The relative height of this film is exaggerated in
The ultrasonic transducer 24 emits an ultrasonic beam 25 with a frequency, in an embodiment, in excess of 1 MHz and potentially as high as 50 MHz through the gas (e.g., air) present under the liquid confinement structure 22 and onto the substrate. The ultrasonic beam 25 atomizes the liquid layer 11a and frees the liquid from the surface of the substrate. The liquid is removed substantially without cooling of the substrate, by atomization and transportation of the atomized liquid. Evaporation, as does occur, will likely not directly affect the substrate. A flow of gas (e.g. air) 27 may be provided by gas supply 26 to carry the atomized liquid toward the seal device 23 and prevent it from escaping to parts of the apparatus where it may be undesirable. An extractive part of the seal device 23 may set up sufficient gas flow to perform this function in one or more embodiments of the invention.
In an embodiment, the ultrasonic transducer 24 is formed by two separately driven parts 24a, 24b. The relative phases of these parts may be controlled to focus the ultrasonic beam at the surface of the liquid layer 11a. A sensor 28, e.g. a an acoustic or optical sensor, may be provided to detect the presence of liquid layer 11a and/or the position of its top surface. Additionally or alternatively, the sensor 28 may be used to control the amplitude, frequency and/or phase of the two parts 24a, 24b of the ultrasonic transducer to ensure efficient and effective removal of the liquid layer without excessive heat generation and to control the size of the liquid droplets generated, which may be a function of frequency of the ultrasonic beam. Interference effects between beams emitted by the two parts of the transducer may be exploited to enhance atomization. Harmonics of the principal frequency may be used to enhance the removal effect. Although several tens of Watts of power may be input to the transducer per cm2 of substrate where liquid is to be removed, the frequency of the ultrasonic beam(s) is sufficiently high not to disturb the lithographic apparatus.
Suitable types of transducers include piezo-electric, piezo-strictive, magneto-strictive and capacitive transducers. Multiple transducers may be spaced around the liquid confinement structure 22 according to its geometry and the expected directions of movement of the substrate. Interdigitated transducers may be used and several concentric rings of transducers may be used if required.
In place of a sensor to detect the liquid layer 11a, the impedance of the transducer(s) may be monitored as proper coupling of the ultrasonic beam 25 into the liquid layer 11a will cause a change of impedance in the transducer 24.
In European Patent Application No. 03257072.3, the idea of a twin or dual stage immersion lithography apparatus is disclosed. Such an apparatus is provided with two tables for supporting a substrate. Leveling measurements are carried out with a table at a first position, without inversion liquid, and exposure is carried out with a table at a second position, where immersion liquid is present. Alternatively, the apparatus has only one table.
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.
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, 248, 193, 157 or 126 nm).
The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive and reflective 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.
One or more embodiments of the present invention may be applied to any immersion lithography apparatus, in particular, but not exclusively, to those types mentioned above. A liquid supply system is any mechanism that provides a liquid to a space between the projection system and the substrate and/or substrate table. It may comprise any combination of one or more structures, one or more liquid inlets, one or more gas inlets, one or more gas outlets, and/or one or more liquid outlets, the combination providing and confining the liquid to the space. In an embodiment, a surface of the space may be limited to a portion of the substrate and/or substrate table, a surface of the space may completely cover a surface of the substrate and/or substrate table, or the space may envelop the substrate and/or substrate table.
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.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3573975 | Dhaka et al. | Apr 1971 | A |
| 3648587 | Stevens | Mar 1972 | A |
| 4346164 | Tabarelli et al. | Aug 1982 | A |
| 4390273 | Loebach et al. | Jun 1983 | A |
| 4396705 | Akeyama et al. | Aug 1983 | A |
| 4480910 | Takanashi et al. | Nov 1984 | A |
| 4509852 | Tabarelli et al. | Apr 1985 | A |
| 5040020 | Rauschenbach et al. | Aug 1991 | A |
| 5610683 | Takahashi | Mar 1997 | A |
| 5715039 | Fukuda et al. | Feb 1998 | A |
| 5825043 | Suwa | Oct 1998 | A |
| 5900354 | Batchelder | May 1999 | A |
| 6191429 | Suwa | Feb 2001 | B1 |
| 6236634 | Lee et al. | May 2001 | B1 |
| 6560032 | Hatano | May 2003 | B2 |
| 6600547 | Watson et al. | Jul 2003 | B2 |
| 6603130 | Bisschops et al. | Aug 2003 | B1 |
| 6633365 | Suenaga | Oct 2003 | B2 |
| 6662812 | Hertz et al. | Dec 2003 | B1 |
| 7014966 | Pawloski et al. | Mar 2006 | B2 |
| 20020020821 | Van Santen et al. | Feb 2002 | A1 |
| 20020163629 | Switkes et al. | Nov 2002 | A1 |
| 20030123040 | Almogy | Jul 2003 | A1 |
| 20030174408 | Rostalski et al. | Sep 2003 | A1 |
| 20040000627 | Schuster | Jan 2004 | A1 |
| 20040021844 | Suenaga | Feb 2004 | A1 |
| 20040075895 | Lin | Apr 2004 | A1 |
| 20040109237 | Epple et al. | Jun 2004 | A1 |
| 20040114117 | Bleeker | Jun 2004 | A1 |
| 20040119954 | Kawashima et al. | Jun 2004 | A1 |
| 20040125351 | Krautschik | Jul 2004 | A1 |
| 20040135099 | Simon et al. | Jul 2004 | A1 |
| 20040136494 | Lof et al. | Jul 2004 | A1 |
| 20040160582 | De Smit et al. | Aug 2004 | A1 |
| 20040165159 | Lof et al. | Aug 2004 | A1 |
| 20040207824 | Lof et al. | Oct 2004 | A1 |
| 20040211920 | Derksen et al. | Oct 2004 | A1 |
| 20050024609 | De Smit et al. | Feb 2005 | A1 |
| 20070132969 | Gellrich et al. | Jun 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 206 607 | Feb 1984 | DE |
| 221 563 | Apr 1985 | DE |
| 224448 | Jul 1985 | DE |
| 242880 | Feb 1987 | DE |
| 0023231 | Feb 1981 | EP |
| 0418427 | Mar 1991 | EP |
| 1039511 | Sep 2000 | EP |
| 2474708 | Jul 1981 | FR |
| 58-202448 | Nov 1983 | JP |
| 62-065326 | Mar 1987 | JP |
| 62-121417 | Jun 1987 | JP |
| 63-157419 | Jun 1988 | JP |
| 04-305915 | Oct 1992 | JP |
| 04-305917 | Oct 1992 | JP |
| 06-124873 | May 1994 | JP |
| 07-132262 | May 1995 | JP |
| 07-220990 | Aug 1995 | JP |
| 10-228661 | Aug 1998 | JP |
| 10-255319 | Sep 1998 | JP |
| 10-303114 | Nov 1998 | JP |
| 10-340846 | Dec 1998 | JP |
| 11-176727 | Jul 1999 | JP |
| 2000-058436 | Feb 2000 | JP |
| 2001-091849 | Apr 2001 | JP |
| 2004-193252 | Jul 2004 | JP |
| WO 9949504 | Sep 1999 | WO |
| WO 03077036 | Sep 2003 | WO |
| WO 03077037 | Sep 2003 | WO |
| WO 2004019128 | Mar 2004 | WO |
| WO 2004053596 | Jun 2004 | WO |
| WO 2004053950 | Jun 2004 | WO |
| WO 2004053951 | Jun 2004 | WO |
| WO 2004053952 | Jun 2004 | WO |
| WO 2004053953 | Jun 2004 | WO |
| WO 2004053954 | Jun 2004 | WO |
| WO 2004053955 | Jun 2004 | WO |
| WO 2004053956 | Jun 2004 | WO |
| WO 2004053957 | Jun 2004 | WO |
| WO 2004053958 | Jun 2004 | WO |
| WO 2004053959 | Jun 2004 | WO |
| WO 2004055803 | Jul 2004 | WO |
| WO 2004057589 | Jul 2004 | WO |
| WO 2004057590 | Jul 2004 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20060103816 A1 | May 2006 | US |
