CN110678812B - Lithographic apparatus - Google Patents

Lithographic apparatus Download PDF

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Publication number
CN110678812B
CN110678812B CN201880036358.6A CN201880036358A CN110678812B CN 110678812 B CN110678812 B CN 110678812B CN 201880036358 A CN201880036358 A CN 201880036358A CN 110678812 B CN110678812 B CN 110678812B
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China
Prior art keywords
cleaning fluid
channel
fluid inlet
wall
chamber
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CN201880036358.6A
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Chinese (zh)
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CN110678812A (en
Inventor
H·G·希梅尔
J·M·A·霍夫曼
M·兰詹
P·A·M·加塞林
A·L·C·勒鲁
M·尤塞菲莫格哈德丹
E·J·阿尔勒马克
D·V·P·汉斯乔特
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ASML Holding NV
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ASML Holding NV
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/70858—Environment aspects, e.g. pressure of beam-path gas, temperature
    • G03F7/70866—Environment aspects, e.g. pressure of beam-path gas, temperature of mask or workpiece
    • G03F7/70875—Temperature, e.g. temperature control of masks or workpieces via control of stage temperature
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/70908—Hygiene, e.g. preventing apparatus pollution, mitigating effect of pollution or removing pollutants from apparatus
    • G03F7/70916—Pollution mitigation, i.e. mitigating effect of contamination or debris, e.g. foil traps
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/70908—Hygiene, e.g. preventing apparatus pollution, mitigating effect of pollution or removing pollutants from apparatus
    • G03F7/70933—Purge, e.g. exchanging fluid or gas to remove pollutants

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  • Health & Medical Sciences (AREA)
  • Epidemiology (AREA)
  • Public Health (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Atmospheric Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Toxicology (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)

Abstract

A lithographic apparatus comprising: a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate; a second chamber comprising a substrate table configured to hold a substrate; a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of cleaning fluid, a perimeter of the channel defined by a wall; and a cooling system configured to cool the wall of the channel.

Description

Lithographic apparatus
Cross Reference to Related Applications
The present application claims priority from european application 17173276.1 filed on 5.29 in 2017, the entire contents of which are incorporated herein by reference.
Technical Field
The application relates to a lithographic apparatus and a device manufacturing method.
Background
A lithographic apparatus is a machine that is configured to apply a desired pattern onto a substrate. For example, lithographic apparatus can be used to manufacture Integrated Circuits (ICs). The lithographic apparatus may, for example, project a pattern from a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on the substrate.
The wavelength of the radiation used by the lithographic apparatus to project the pattern onto the substrate determines the smallest dimension of a feature that can be formed on the substrate. Lithographic apparatus using EUV radiation (electromagnetic radiation having a wavelength in the range of 4-20 nm) may be used to form smaller features on a substrate than conventional lithographic apparatus (e.g., electromagnetic radiation having a wavelength of 193nm may be used).
A projection system of a lithographic apparatus may be held in a first chamber and a substrate table of the lithographic apparatus may be held in a second chamber. The first chamber and the second chamber may be maintained under vacuum conditions to reduce unwanted EUV radiation absorption. Since the projection system is very sensitive to contaminants, whereas the second chamber is for example a source of contaminants, for example by degassing of the resist or of a cable connected to a movable part, such as a substrate table, the first chamber may be kept at a lower pressure than the second chamber.
A channel may be provided between the first chamber and the second chamber, the periphery of the channel being defined by the wall. The channel may be provided with a flow of cleaning fluid configured to act as a curtain of cleaning fluid between the first chamber and the second chamber. The cleaning fluid curtain may be configured to reduce an amount of contamination from the second chamber to the first chamber. It may be desirable to provide a channel that obviates or mitigates one or more problems of the prior art, whether referred to herein or elsewhere.
Disclosure of Invention
According to a first aspect of the invention, there is provided a lithographic apparatus comprising: a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate; a second chamber comprising a substrate table configured to hold a substrate; a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of cleaning fluid, a perimeter of the channel defined by a wall; and a cooling system configured to cool the wall of the channel.
Cooling the walls of the channels advantageously cools the cleaning fluid with a higher efficiency than uncooled walls and allows for better control of the temperature of the cleaning fluid over a larger temperature range. The walls of the cooling channels reduce heat transfer from the cleaning fluid to the substrate, thereby reducing lithographic errors associated with thermal expansion of the substrate. The walls of the cooling channels also reduce variations in lithographic errors between different lithographic apparatus caused by heat transfer from the cleaning fluid to the substrate. The walls of the cooling channels advantageously increase the mass flow of the cleaning fluid to the second chamber and reduce the diffusion coefficient of the cleaning fluid for diffusion of contaminants from the second chamber to the first chamber, thereby reducing the cleaning fluid flow required to achieve the desired level of contaminant suppression. The walls of the cooling channels advantageously reduce the dependence of the cooling system on the flow of cleaning fluid provided to the channels and reduce the vacuum requirements of the first chamber and/or the second chamber, thereby reducing the operating costs of the lithographic apparatus.
The cooling system includes a dedicated thermal conductor in thermal communication with the wall of the channel.
As used herein, the term "dedicated" is intended to indicate that the only function of the thermal conductor is to conduct heat.
The dedicated thermal conductor may comprise a heat pipe.
The heat pipe advantageously provides for efficient heat transfer away from the channel wall compared to other known heat conductors.
The dedicated thermal conductor may comprise two or more heat pipes connected in parallel.
The cooling system may further include a heat exchanger in thermal communication with the dedicated thermal conductor.
The cooling system is configured to cool the cleaning fluid before the cleaning fluid flows to the channel via the conduit.
The cleaning fluid is cooled before it travels to the channel via the pipe and cools the walls of the channel, which causes the walls of the channel to cool the cleaning fluid in the channel, which advantageously reduces the dependency of the cooling system on the flow of cleaning fluid provided to the channel.
The cooling system may include a mount configured to provide a thermally conductive path between the dedicated thermal conductor and the wall of the channel.
The mount may include an attachment structure configured to enable removal and reattachment of the cooling system to the wall of the channel.
The attachment structure may include threads for receiving a bolt.
The cooling system may also further include a controller configured to measure a temperature of the wall of the channel and output a signal indicative of the temperature of the wall of the channel, and a temperature sensor configured to receive a signal from the temperature sensor and adjust the cooling provided by the cooling system based on the signal received from the temperature sensor.
The controller may be a proportional-integral-derivative controller.
A cooling system may be configured to cool a portion of the wall of the channel.
The portion of the wall of the channel may be located below the cleaning fluid inlet of the wall of the channel.
Cooling the cleaning fluid below the cleaning fluid inlet increases the density of the cleaning fluid below the cleaning fluid inlet, which advantageously increases the partial flow of the cleaning fluid to the second chamber, thereby providing greater containment of contaminants.
The lithographic apparatus may further comprise a cooling apparatus configured to cool a region of the substrate, and the cooling system may be configured to cool a portion of the cooling apparatus.
The lithographic apparatus may further comprise a heating system configured to heat a portion of the wall of the channel above the cleaning fluid inlet of the wall of the channel.
A portion of the wall of the heating channel above the cleaning fluid inlet may advantageously reduce the amount of contamination from the second chamber to the first chamber. This is because thermal expansion of the cleaning fluid over the cleaning fluid inlet causes an increase in the flow of cleaning fluid towards the second chamber. Increasing the proportion of the flow of cleaning fluid travelling towards the second chamber advantageously reduces the amount of contaminants reaching the first chamber from the second chamber.
According to a second aspect of the invention, there is provided a lithographic apparatus comprising: a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate; a second chamber comprising a substrate table configured to hold a substrate; a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of cleaning fluid, a perimeter of the channel defined by a wall, the wall of the channel including a cleaning fluid inlet; wherein the purging fluid inlet includes a restrictor configured to allow different sections of the purging fluid inlet to provide different flows of purging fluid to the channel.
Providing a restrictor to allow different sections of the cleaning fluid inlet to provide different cleaning fluid flows to the cleaning channel advantageously reduces non-uniformity of the cleaning fluid within the channel. This reduces the amount of contamination from the second chamber to the first chamber. Reducing non-uniformity in the flow of the cleaning fluid within the channels may allow for a lower total flow of cleaning fluid to be used.
The flow restrictor may include a baffle configured to divide the cleaning fluid inlet into the different segments.
The restrictor may include a varying cleaning fluid inlet opening size such that the different sections of the cleaning fluid inlet have different opening sizes.
The use of varying opening sizes of the cleaning fluid inlet advantageously allows the flow rate of the cleaning fluid to vary more continuously around the cleaning fluid inlet of the channel than if baffles were used.
According to a third aspect of the invention, there is provided a lithographic apparatus comprising: a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate; a second chamber comprising a substrate table configured to hold a substrate; a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of cleaning fluid, a perimeter of the channel defined by a wall, the wall of the channel including an angled cleaning fluid inlet; wherein the inner wall of the angled cleaning fluid inlet is curved.
The phrase "angled cleaning fluid inlet" as used herein is intended to mean that the injection angle of the cleaning fluid inlet (i.e. the angle between the line bisecting the angled cleaning fluid inlet and the optical axis of the lithographic apparatus) may not be perpendicular at all positions around the cleaning fluid inlet. For example, the injection angle may be an acute angle. The inclusion of an angled inlet having a curved inner wall advantageously increases the momentum of the cleaning fluid traveling toward the second chamber, thereby reducing the amount of contamination from the second chamber to the first chamber.
The inner wall of the cleaning fluid inlet may be curved such that there is a smooth transition from the curved inner wall of the cleaning fluid inlet to the wall of the channel.
The smooth transition from the inner wall of the cleaning fluid inlet to the channel wall advantageously reduces the separation of the upward flow of small cleaning fluid towards the first chamber and the downward flow towards the second chamber. That is, a greater proportion of the cleaning fluid flow may exit the angled cleaning fluid inlet and travel toward the second chamber, which in turn may advantageously reduce the amount of contamination from the second chamber to the first chamber.
The inner wall of the cleaning fluid inlet may be curved such that the cleaning fluid inlet defines a converging flow path for the cleaning fluid.
The converging flow path of the cleaning fluid defined by the curved inner wall of the cleaning fluid inlet advantageously promotes acceleration of the cleaning fluid towards the second chamber. This reduces the amount of contamination from the second chamber to the first chamber.
The inner wall of the cleaning fluid inlet may be curved such that the opening size of the cleaning fluid inlet is narrowest at or before the end of the cleaning fluid inlet.
The narrowest opening dimension of the cleaning fluid inlet at or before the end of the cleaning fluid inlet advantageously facilitates further acceleration of the cleaning fluid towards the second chamber, which reduces the amount of contamination from the second chamber to the first chamber.
The distance between the lower wall of the cleaning fluid inlet and the substrate table is greater than about 15mm.
According to a fourth aspect of the invention, there is provided a lithographic apparatus comprising: a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate; a second chamber comprising a substrate table configured to hold a substrate; a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of cleaning fluid, a perimeter of the channel defined by a wall, the wall of the channel including a first cleaning fluid inlet and a second cleaning fluid inlet, the second cleaning fluid inlet being positioned closer to the substrate than the first cleaning fluid inlet. The controller is configured to control a flow rate of the cleaning fluid provided through the first cleaning fluid inlet and a flow rate of the cleaning fluid provided through the second cleaning fluid inlet, wherein the controller is configured to control the flow rate of the cleaning fluid provided through the second cleaning fluid inlet based on the flow rate of the cleaning fluid flowing from the channel to the second chamber when substantially no cleaning fluid flow is provided through the second cleaning fluid inlet.
Providing a flow of cleaning fluid is based on a flow of cleaning fluid from the channel to the second chamber when substantially no cleaning fluid is provided through the second cleaning fluid inlet, which advantageously reduces recirculation of cleaning fluid within the channel. This reduces the amount of contamination travelling up the walls of the channel from the second chamber to the first chamber.
The controller is configured to provide a flow of cleaning fluid through the second cleaning fluid inlet that is between about 50% and about 200% of the flow of cleaning fluid from the channel to the second chamber when substantially no cleaning fluid flow is provided through the second cleaning fluid inlet. This flow range was found to provide improved pollution suppression.
According to a fifth aspect of the present invention, there is provided a device manufacturing method using a lithographic apparatus, the method comprising: projecting the patterned radiation beam onto a substrate using a projection system in the first chamber; supporting the substrate using a substrate table in the second chamber; providing a channel extending between the first chamber and the second chamber, the channel being peripherally defined by a wall; providing a flow of cleaning fluid to the channel and cooling the walls of the channel.
The walls of the channels may be cooled by dedicated heat conductors. The dedicated thermal conductor may comprise one or more heat pipes.
The method may further comprise cooling the cleaning fluid before the cleaning fluid reaches the channel.
The method may further comprise measuring a temperature of the wall of the channel and controlling cooling of the wall of the channel based on the measured temperature of the wall of the channel.
The method may further comprise cooling a portion of the wall of the channel below the cleaning fluid inlet of the wall of the channel.
The method may further comprise heating a portion of the wall of the channel above a cleaning fluid inlet of the wall of the channel.
The method may further comprise cooling the walls of the channel to a temperature between about 8 ℃ and about 15 ℃.
The method may further comprise calibrating the cooling of the walls of the channel such that a relationship between the temperature of the walls of the channel and an overlay error of the lithographic exposure occurring during the cooling of the walls of the channel is determined, wherein the calibrating comprises a first step of cooling the walls to a desired temperature, a second step of performing the lithographic exposure on the substrate, and a third step of processing the substrate and measuring the overlay error of the lithographic exposure.
According to a sixth aspect of the present invention, there is provided a device manufacturing method using a lithographic apparatus, the method comprising: projecting the patterned radiation beam onto a substrate using a projection system in the first chamber; supporting the substrate using a substrate table in the second chamber; providing a channel extending between the first chamber and the second chamber, the channel being peripherally defined by a wall; and providing different flows of cleaning fluid to the channel through different sections of the cleaning fluid inlet of the wall of the channel.
The flow rate of the cleaning fluid provided to the different sections of the cleaning fluid inlet may depend at least in part on the ratio of the size of the cross-sectional area of the channel to the total length of the cleaning fluid inlet section providing cleaning fluid to the cross-sectional area of the channel. The method advantageously achieves a more uniform flow of cleaning fluid within the channel, thereby reducing the amount of contamination from the second chamber to the first chamber.
According to a seventh aspect of the present invention, there is provided a device manufacturing method using a lithographic apparatus, the method comprising: projecting a patterned beam of radiation onto a substrate supported by a substrate table in a second chamber using a projection system in a first chamber, the patterned beam of radiation reaching the second chamber from the first chamber via a channel, the periphery of the channel being defined by walls in which an angled cleaning fluid inlet having curved inner walls is provided, wherein the method further comprises providing cleaning fluid into the channel through the angled cleaning fluid inlet.
The inner wall of the cleaning fluid inlet is curved such that cleaning fluid flows along a converging flow path.
According to an eighth aspect of the present invention, there is provided a device manufacturing method using a lithographic apparatus, the method comprising: projecting the patterned radiation beam onto a substrate using a projection system in the first chamber; supporting the substrate using a substrate table in the second chamber; providing a channel extending between the first chamber and the second chamber, the channel being peripherally defined by a wall; providing a cleaning fluid to the walls of the channel from a first cleaning fluid inlet and a second cleaning fluid inlet, the second cleaning fluid inlet being positioned closer to the substrate than the first cleaning fluid inlet; and providing a cleaning fluid through the second cleaning fluid inlet, wherein a flow rate of cleaning fluid is based on a flow rate of cleaning fluid flowing from the channel to the second chamber when substantially no cleaning fluid is provided through the second cleaning fluid inlet.
The method may further comprise: providing a flow of cleaning fluid through the second cleaning fluid inlet, the flow of cleaning fluid provided being substantially equal to the flow of cleaning fluid from the channel to the second chamber when substantially no cleaning fluid is provided through the second cleaning fluid inlet.
Drawings
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which:
FIG. 1 schematically depicts a lithographic system comprising a lithographic apparatus, a radiation source and a channel, which may comprise an embodiment of the invention;
figure 2 schematically shows a known channel and purge fluid pre-cooling system;
figure 3 schematically shows a cooling system and channels according to an embodiment of the invention;
fig. 4 schematically shows a cooling system and channels according to an embodiment of the invention;
fig. 5 schematically shows a view from the opening of a known channel;
figure 6 schematically shows a top view of a channel according to an embodiment of the invention, the channel comprising a cleaning fluid inlet with a restrictor;
figure 7 schematically shows a cross-sectional view of a segment of a cleaning fluid inlet comprising a flow restrictor according to an embodiment of the present invention;
fig. 8 schematically shows a cross-section from the side of a known channel;
figure 9 schematically shows a cross-sectional view from the side of a channel comprising an angled cleaning fluid inlet according to an embodiment of the invention;
figure 10 schematically shows a cross-sectional perspective view of a channel comprising an angled cleaning fluid inlet according to an embodiment of the invention;
Fig. 11 schematically shows the known channel shown in fig. 8, wherein it can be seen that the washing fluid flows out of the washing fluid inlet;
figure 12 schematically shows a channel comprising a plurality of cleaning fluid inlets according to an embodiment of the invention; and
fig. 13 schematically shows a perspective view of a channel comprising a plurality of washing fluid inlets and a cooling system according to an embodiment of the invention.
Detailed Description
FIG. 1 depicts a lithographic system with channels that includes an embodiment of the present invention. The lithographic system includes a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an Extreme Ultraviolet (EUV) radiation beam B. The lithographic apparatus LA includes an illumination system IL, a support structure MT configured to support a patterning device MA (e.g. a mask), a projection system PS, and a substrate table WT configured to support a substrate W. The illumination system IL is configured to condition the radiation beam B before it is incident on the patterning device MA. The projection system is configured to project a radiation beam B (which is now patterned by the mask MA) onto a substrate W. The substrate W may include a previously formed pattern. In this case, the lithographic apparatus aligns the patterned beam of radiation B with a pattern previously formed on the substrate W.
The radiation source SO, the illumination system IL, and the projection system PS may be constructed and arranged SO that they are isolated from the external environment. A gas at a sub-atmospheric pressure (e.g. hydrogen) may be provided in the radiation source SO. A vacuum may be provided in the illumination system IL and/or the projection system PS. A small amount of gas (e.g., hydrogen) at a pressure well below atmospheric pressure may be provided in the illumination system IL and/or the projection system PS.
The type of radiation source SO shown in FIG. 1 may be referred to as a laser-produced plasmaA daughter (LPP) source. The laser 1 (which may be CO, for example 2 A laser) is arranged to deposit energy into the fuel by means of a laser beam 2, such as tin (Sn) supplied from a fuel emitter 3. Although tin is mentioned in the following description, any suitable fuel may be used. The fuel may be, for example, in liquid form, and may be, for example, a metal or alloy. The fuel emitter 3 may include a nozzle configured to direct tin (e.g., tin in the form of droplets) along a trajectory toward the plasma formation region 4. The laser beam 2 is incident on tin at the plasma formation region 4. Laser energy is deposited into the tin to generate a plasma 7 at the plasma formation region 4. During de-excitation and recombination of ions of the plasma, radiation, including EUV radiation, is emitted from the plasma 7.
EUV radiation is collected and focused by a near normal incidence radiation collector 5 (sometimes more commonly referred to as a normal incidence radiation collector). The collector 5 may have a multi-layered structure arranged to reflect EUV radiation (e.g. EUV radiation having a desired wavelength, such as 13.5 nm). The collector 5 may have an elliptical configuration with two elliptical foci. The first focus may be at the plasma formation region 4 and the second focus may be at the intermediate focus 6, as described below.
The laser 1 may be separate from the radiation source SO. In this case, the laser beam 2 may be transferred from the laser 1 to the radiation source SO by means of a beam delivery system (not shown) comprising, for example, suitable directing mirrors and/or beam expanders, and/or other optical devices. The laser 1 and the radiation source SO may together be considered as a radiation system.
The radiation reflected by the collector 5 forms a radiation beam B. The radiation beam B is focused at a point 6 to form an image of the plasma formation region 4, which acts as a virtual radiation source for the illumination system IL. The point 6 at which the radiation beam B is focused may be referred to as the intermediate focus. The radiation source SO is arranged such that the intermediate focus 6 is located at or near an opening 8 in a closed structure 9 of the radiation source.
The radiation beam B enters the illumination system IL from the radiation source SO, which is configured to condition the radiation beam. The illumination system IL may include a facet field lens device 10 and a facet pupil lens device 11. Together, the micro-facet field-lens device 10 and the micro-facet pupil mirror device 11 provide a radiation beam B having a desired cross-sectional shape and a desired angular distribution. The radiation beam B is delivered from the illumination system IL and is incident on the patterning device MA, which is held by the support structure MT. Patterning device MA reflects and patterns radiation beam B. In addition to or in lieu of facet field lens device 10 and facet pupil lens device 11, illumination system IL may include other mirrors or devices.
After being reflected by patterning device MA, patterned radiation beam B enters projection system PS. The projection system PS comprises a plurality of mirrors 13, 14, the mirrors 15, 16 being configured to project a radiation beam onto a substrate W held by the substrate table WT. The projection system PS can apply a reduction factor to the radiation beam to form an image having features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 may be applied. The reduction factor may vary for different directions, i.e. the reduction factor in the x-direction may be different from the reduction factor in the y-direction. Although the projection system PS has two mirrors 13, 14 in fig. 1, the projection system may include any number of mirrors (e.g., six mirrors).
The radiation source SO shown in FIG. 1 may include components not shown. For example, a spectral filter may be provided in the radiation source. The spectral filter may be substantially transmissive to EUV radiation, but substantially blocking radiation of other wavelengths, such as infrared radiation.
The projection system PS of the lithographic apparatus is held in a first chamber 15 and the substrate table WT is held in a second chamber 16. The first chamber 15 and the second chamber 16 are maintained under vacuum. Contaminants may be generated in the second chamber 16 and diffuse to the first chamber 15. For example, hydrocarbons and/or metals (e.g., tin) may escape from the resist on the substrate W and travel toward highly sensitive optical components in the projection system PS. Exposing the substrate to EUV radiation may result in an increase in the amount of contaminants generated in the second chamber 16. Contaminants may diffuse from the second chamber 16 to the first chamber 15. Contaminants may accumulate on the optical components in projection system PS, thereby negatively affecting the performance of the optical components. For example, contaminants may accumulate on the reflective surfaces of the mirrors in the projection system PS and reduce the reflectivity of the mirrors. The reduction in reflectivity of the mirrors in the projection system PS may reduce the amount of EUV radiation reaching the substrate W, which in turn may reduce the throughput of the substrate, since a longer time is required for the same EUV dose to be applied to the substrate W.
The known lithographic apparatus comprises a channel 17 extending between the first chamber 15 and the second chamber 16. The channel 17 has a periphery defined by walls 19. The channel 17 may be provided with a flow of cleaning fluid through a cleaning fluid inlet (not shown) provided in the wall 19 of the channel 17. The cleaning fluid may, for example, comprise hydrogen. Other fluids may be used, such as helium, nitrogen, argon, and/or any mixtures thereof. A cleaning fluid having a low diffusion coefficient (e.g., lower than the diffusion coefficient of hydrogen) for contaminants present in the lithographic apparatus may be selected.
In use, a portion of the cleaning fluid flows through the passage 17 to the second chamber 16 and another portion of the cleaning fluid flows through the passage 17 to the first chamber 15. A first exhaust system (not shown) is provided in the first chamber 15 to remove the cleaning fluid from the first chamber 15. A second exhaust system (not shown) is provided in the second chamber 16 to remove the cleaning fluid from the second chamber 16. The portion of the flow of cleaning fluid that passes through the channel 17 towards the second chamber 16 forms a curtain of cleaning fluid. The cleaning fluid curtain is configured to reduce the amount of contaminants reaching the second chamber 16 from the first chamber 15, thereby protecting the projection system PS from contamination. The channel 17 and the cleaning fluid curtain are both configured to allow EUV radiation to pass from the first chamber 15 to the second chamber 16 so that a lithographic exposure may be performed.
Some lithographic apparatus have a larger numerical aperture than others. An increase in the numerical aperture of the lithographic apparatus may negatively affect the ability of the channel 17 and the cleaning fluid curtain to reduce contamination of the first chamber 15. An increase in the numerical aperture of the lithographic apparatus may result in an increase in the opening between the first chamber 15 and the second chamber 16, which may result in a widening of the channel 17. Increasing the width of the channel 17 may reduce the flow of cleaning fluid traveling towards the second chamber 16. Increasing the width of the channel 17 increases the cross-sectional area of the channel 17, thereby providing a larger cross-sectional area for the diffusion of contaminants from the second chamber 16 to the first chamber 15.
Some lithographic apparatus include a cooling apparatus (not shown) configured to cool an area of the substrate W near an exposure target area of the substrate W. The presence of the cooling device may limit at least a partial outflow of the cleaning fluid exiting the second chamber 16 via the second exhaust system. Limiting the partial outflow of the cleaning fluid from the second chamber 16 reduces the ability of the curtain of cleaning fluid to reduce the amount of contaminants reaching the first chamber 15 from the second chamber 16.
The ability of a lithographic apparatus having a larger numerical aperture (e.g., 0.5) and/or having a cooling apparatus that restricts the flow of cleaning fluid in the second chamber 16 to inhibit contamination may be reduced compared to a lithographic apparatus having a smaller numerical aperture (e.g., 0.3) and no cooling apparatus.
Fig. 2 schematically shows a known channel 17 and a cleaning fluid pre-cooling system 20. A channel 17 extends between the first chamber 15 and the second chamber 16. The periphery of the channel 17 is defined by a wall 19. The projection system PS of the lithographic apparatus is held in a first chamber 15 and the substrate table WT is held in a second chamber 16. In some embodiments, the membrane 18 may extend across the channel 17. Channel 17 is configured to receive a flow of cleaning fluid 23. The cleaning fluid 23 passes from the source 21 through the heat exchanger 22. The heat exchanger 22 is configured to cool the cleaning fluid 23 before the cleaning fluid reaches the channels 17. The cleaning fluid 23 may, for example, have an ambient temperature of about 22 ℃ before reaching the heat exchanger 22. The heat exchanger 22 may, for example, pre-cool the cleaning fluid 23 such that the temperature of the cleaning fluid is reduced from about 22 ℃ to about-10 ℃. The pre-cooled washing fluid 23 then proceeds to the channel 17 via a line 24. Cleaning fluid 23 enters the channel through cleaning fluid inlet 29. The cleaning fluid inlet 29 extends along the periphery of the channel 17. For ease of illustration, the cleaning fluid inlet 29 is shown on only one side of the channel 17 shown in fig. 2. The pre-cooled cleaning fluid flows through the channels 17 and forms a curtain 25 of cleaning fluid, the curtain 25 of cleaning fluid being configured to reduce the amount of contaminants reaching the first chamber 15 from the second chamber 16. Is provided to let in The flow rate of the cleaning fluid 23 of the channels 17 may depend at least in part on the numerical aperture of the lithographic apparatus. For example, the flow rate of the cleaning fluid 23 provided to a lithographic apparatus having a relatively small numerical aperture (e.g., about 0.3) may be, for example, at about 10mbar -1 Up to about 150mbar -1 Between, for example, about 115mbar ls -1 . The flow rate of the cleaning fluid 23 provided to a lithographic apparatus having a relatively large numerical aperture (e.g., about 0.5) may be, for example, up to about 300mbar -1 . Increasing the flow of cleaning fluid provided to the channel 17 may reduce the amount of contamination from the second chamber 16 to the first chamber 15. However, the flow of cleaning fluid 23 provided to the channels 17 may be limited by the vacuum requirements of the first chamber 15 and/or the vacuum requirements of the second chamber 16.
The pre-cooled cleaning fluid 23 may gain thermal energy through one or more mechanisms as it travels from the heat exchanger 22 to the channels 17. For example, heat may be transferred to the pre-cooled cleaning fluid 23 via heat leak 26 from the hotter portions of the lithographic apparatus 28. As another example, friction-induced heating of the cleaning fluid 23 may occur as the cleaning fluid flows from the heat exchanger 22 to the channels 17. The fluid dynamics may also cause certain portions of the flow of cleaning fluid 23 to be at a higher temperature than other portions of the flow of cleaning fluid. For example, a relatively stagnant portion of the flow of cleaning fluid may be at a higher temperature than other portions of the flow of cleaning fluid.
Due to the effect of the heat transfer mechanism discussed above, the cleaning fluid 23 reaches the channels 17 at a temperature higher than the desired temperature. For example, the cleaning fluid 23 may exit the heat exchanger 22 at a temperature of about-10 ℃ and obtain thermal energy as it travels from the heat exchanger 22 to the channel 17, such that the cleaning fluid has a temperature in the range of about 0 ℃ to about 22 ℃ when the cleaning fluid is in the channel 17. The amount of thermal energy obtained by the cleaning fluid 23 may vary between different lithographic apparatus as it travels from the heat exchanger 22 to the channel 17.
When the cleaning fluid reaches the substrate W, some thermal energy may be transferred from the cleaning fluid 23 to the substrate W. The amount of thermal energy transferred from the cleaning fluid 23 to the substrate W depends on specific variables in various situations, such as the lithographic apparatus 28 and the ambient temperature of the cleaning fluid 23, the temperature to which the cleaning fluid 23 is cooled, the amount of heat transferred to the cleaning fluid 23 via the heat leak 26 as it travels from the heat exchanger 22 to the channel 17, the flow rate and type of fluid used as the cleaning fluid, etc.
One variable that affects the amount of heat transfer from the cleaning fluid to the substrate W is the presence of the membrane 18 in the channel 17. In the example of fig. 2, there is a membrane 18. The film 18 is configured to reduce the amount of radiation reaching the substrate W having undesired wavelengths. For example, the film 18 may be configured to absorb infrared radiation and transmit EUV radiation. The membrane 18 may prevent contaminants from reaching the first chamber 15 via the channel 17 or may substantially reduce the amount of contaminants reaching the first chamber 15 from the second chamber 16. The presence of the membrane 18 in the channel 17 is optional. The membrane 18 may substantially prevent the flow of the cleaning fluid 23 into the first chamber 15. When the membrane 18 is present, a flow of cleaning fluid 23 may be provided in the channel 17 to reduce contamination of the membrane 18. Contamination of the film 18 may result in reduced transmission of the desired radiation wavelength through the film 18. The flow rate of the cleaning fluid 23 provided to the channels 17 when the membrane 18 is present may be lower than the flow rate of the cleaning fluid 23 provided to the channels 17 when the membrane 18 is not present. When the membrane 18 is present, a decrease in the flow of the cleaning fluid 23 in the channel 17 results in an increase in the heat transferred from the cleaning fluid to the substrate W. For example, when the membrane 18 is present and the flow rate of the cleaning fluid is thus low, the cleaning fluid 23 may deliver power up to about 400mW to the substrate W. When the membrane 18 is absent and the flow rate of the cleaning fluid is thus high, the cleaning fluid 23 may transfer power up to about 100mW to the substrate W.
The substrate W may be at ambient temperature of the lithographic apparatus. For example, the lithographic apparatus and the substrate W may both have an ambient temperature of about 22 ℃. The thermal energy transferred from the cleaning fluid 23 to the substrate W may cause the substrate to experience thermal deformations, which may lead to lithographic errors, such as overlay errors during lithographic exposure. If the film 18 is not present, the transfer of thermal energy from the cleaning fluid 23 to the substrate W may, for example, result in overlay errors between about 0.1nm and about 0.8 nm. The transfer of thermal energy from the cleaning fluid 23 to the substrate W, if the film 18 is present, may, for example, result in overlay errors between about 0.1nm and about 1.5 nm.
Fig. 3 schematically shows a cooling system 30 and a channel 31 according to an embodiment of the invention. The cooling system 30 is configured to cool the walls 36 of the channel 31. The cooling system 30 comprises a heat exchanger 32, which heat exchanger 32 has a cooling zone 33 in thermal communication with a wall 36 of the channel 31. The heat exchanger 32 may, for example, comprise a peltier device. The heat exchanger 32 may be in thermal communication with a wall 36 of the channel 31 via a dedicated heat conductor 34. The dedicated thermal conductor 34 may be configured to provide a thermally conductive path between the cooling region 33 of the heat exchanger 32 and the wall 36 of the channel 31. The dedicated thermal conductor 34 may, for example, comprise a heat pipe 34. In the example of fig. 3, the dedicated thermal conductor 34 comprises two heat pipes connected in parallel. A greater or lesser number of dedicated thermal conductors 34 may be provided. The two heat pipes are in thermal communication with the cooling region of the peltier device. The walls 36 of the channels 31 may be formed of a thermally conductive material such that the cooling power provided by the heat exchanger 32 via the dedicated thermal conductor 34 is spread over the walls 36 of the channels 31. This enables the portion of the wall 36 that is not in direct contact with the thermal conductor 34 to be cooled by the cooling system 30. The walls 36 of the channel 31 may be formed of metal, such as steel, aluminum, and/or titanium.
The selection of the type of heat pipe 34 used with the cooling system 30 may depend, at least in part, on the desired range of operating temperatures of the heat exchanger 32. For example, if the desired operating temperature of the heat exchanger 32 is equal to or less than 0 ℃, then the water-based heat pipe 34 is unsuitable because the water in the heat pipe may freeze during operation. Thus, when an operating temperature of the heat exchanger 32 equal to or below 0 ℃ is desired, an ethanol-based heat pipe 34 may be desired. Alternatively, ammonia-based or carbon dioxide-based heat pipes may be used.
The cooling system 30 may be configured to cool the walls 36 of the channels 31 from an ambient temperature of, for example, about 22 ℃ to a temperature of about 8 ℃ to 15 ℃. Once cooled by the cooling system 30, the walls 36 of the channels 31 reduce the temperature of the cleaning fluid 35 flowing along the walls 36 of the channels 31. That is, the curtain 43 of cleaning fluid formed by the flow of cleaning fluid 35 within the channel 31 is cooled by the walls 36 of the channel. Cleaning fluid 35 enters channel 31 through cleaning fluid inlet 48. The cleaning fluid inlet 48 extends along the periphery of the channel 31. For ease of illustration, the cleaning fluid inlet 48 is shown on only one side of the channel 31 shown in FIG. 3. The cooled walls 36 of the channels 31 may, for example, reduce the temperature of the cleaning fluid 35 from an ambient temperature of about 22 ℃ to a temperature of about 5 ℃ to about 8 ℃.
A membrane (not shown) may be provided in the embodiment of the channel shown in fig. 3. When a membrane is present in the channel 31 such that the flow of cleaning fluid provided to the channel 31 is low (compared to when a higher flow of cleaning fluid is provided to the channel without a membrane in the channel 31), the walls 36 of the channel 31 may be cooled to a lower temperature. For example, the desired temperature set point of the wall 36 of the channel 31 may be between about 5 ℃ to about 15 ℃, depending at least in part on the flow rate of the cleaning fluid in the channel 31. The walls 36 of the cooling channels 31, rather than just pre-cooling the cleaning fluid 35, may cool the cleaning fluid 35 with a higher efficiency, advantageously allowing the temperature of the cleaning fluid 35 to be controlled over a larger temperature range.
The cooling system 30 may optionally be configured to cool the cleaning fluid 35 before the cleaning fluid travels to the channel 31 via the line 37. In the example of fig. 3, the portion of the conduit 37 that directs the cleaning fluid 35 from the source 39 through the heat exchanger 32 to the channel 31 is in thermal communication with the cooling region 33 of the heat exchanger 32 such that the portion of the conduit 37 and the cleaning fluid 35 contained therein is cooled by the cooling region 33 of the heat exchanger 32. The cleaning fluid 35 is cooled before it travels to the channel 31 via the conduit 37 and cools the wall 36 of the channel 31, which causes the wall 36 of the channel 31 to cool the cleaning fluid in the channel 31, which advantageously reduces the dependency of the cooling system 30 on the flow of the cleaning fluid 35 provided to the channel 31.
The cooling system 30 may include a mount 38. The mount 38 may be configured to provide a thermally conductive path between the dedicated thermal conductor 34 and the wall 36 of the channel 31. The mounting member 38 may be formed of metal, such as steel. The mount 38 may include an attachment structure 42, which attachment structure 42 is configured to enable all or a portion of the cooling system 30 to be easily removed and reattached to the wall 36 of the channel 31. The attachment structure 42 may be configured such that the wall 36 of the channel 31 may be removed from the lithographic apparatus without having to also remove the cooling system 30. The attachment structure 42 may, for example, include a blind hole in the wall 36 for receiving a bolt. The mounts 38 advantageously enable simple and quick removal and installation of the walls 36 of the channels 31 in a lithographic apparatus, for example when the walls 36 of the channels 31 need to be removed for installation or replacement or removal of a membrane (not shown). The attachment structure 42 is not necessary. The mounting 38 is not necessary (i.e. the dedicated thermal conductor 34 may be in direct contact with the wall 36 of the channel 31).
The cooling system 30 may include a controller 40. The controller 40 may form part of a feedback loop configured to control the temperature of the wall 36 of the channel 31. The controller 40 may, for example, comprise a Proportional Integral Derivative (PID) controller. The cooling system 30 may be provided with a temperature sensor 41. The temperature sensor 41 may, for example, comprise a thermistor or thermocouple in thermal communication with the wall 36 of the channel 31. The temperature sensor 41 may, for example, have an accuracy of about 0.1K. The temperature sensor 41 may be configured to measure the temperature of the wall 36 of the channel 31 and output a signal indicative of the temperature of the wall 36 of the channel 31 to the controller 40. The controller 40 may be configured to receive the signal from the temperature sensor 41 and adjust the temperature of the cooling region 33 of the heat exchanger 32 based on the signal received from the temperature sensor 41 (e.g., by adjusting the current provided to the peltier device).
The transfer of thermal energy to the substrate W due to absorption of radiation during a lithographic exposure can also be partially or fully compensated when controlling the temperature of the walls 36 of the channels 31. The temperature of the walls 36 of the channels 31 may be controlled so as to reduce overlay errors caused by thermal deformation of the substrate W during lithographic exposure. The cooling system 30 may be calibrated to determine the relationship between the temperature of the walls 36 of the channels 31 and the overlay error of the lithographic exposure that occurs during use of the cooling system 30. Calibration may include multiple steps. The first step may include cooling the walls 36 of the channel 31 to a desired temperature. The second step may comprise performing a photolithographic exposure of the substrate W. A third step may include processing the substrate W and measuring overlay errors of the photolithographic exposure. The three steps may be repeated and the photolithographic exposure performed at different wall 36 temperatures until the desired reduction in overlay error is achieved.
The cooling power provided by the cooling system 30 may be calibrated for different thermal disturbances, e.g. different pressure conditions in the first chamber 15 and the second chamber 16, movement of the movable component (e.g. the substrate table WT) to generate thermal energy by friction, etc. Calibration may include multiple steps. The first step may include cooling the walls 36 of the channel 31 to a desired temperature. The second step may include applying a thermal disturbance, for example, changing the pressure state in one or both of the first chamber 15 and the second chamber 16, or moving a movable component (e.g., substrate table WT). A third step may comprise measuring the temperature change of the walls 36 of the channel 31 due to the applied thermal disturbance. The fourth step may include adjusting the cooling provided by the cooling system 30 to fully or partially compensate for the measured change in temperature of the walls 36 of the channel 31.
Fig. 4 schematically shows a cooling system 50 and a channel 51 according to an embodiment of the invention. In the example of fig. 4, the cooling system 50 is configured to cool a portion 52 of a wall 80 of the channel 51. In the example of fig. 4, the portion 52 of the wall 80 of the channel 51 cooled by the cooling system 50 is indicated by a bold line. The cooling system 50 includes a mount 63 having an attachment structure 62, the attachment structure 62 being configured to enable reversible attachment of the cooling system 50 to a wall 80 of the channel 51. The attachment structure 62 is not necessary. The mounting 63 is not necessary (i.e. the dedicated heat conductor 61 may be in direct contact with the wall 80 of the channel 51). Cleaning fluid 56 enters channel 51 from source 57 through line 58 via cleaning fluid inlet 55. The cleaning fluid inlet 55 extends along the periphery of the channel 51. For ease of illustration, the cleaning fluid inlet 55 is shown on only one side of the channel 51 shown in fig. 4. Some of the cleaning fluid flow in the channel 51 forms a curtain of cleaning fluid 53, which curtain of cleaning fluid 53 is configured to reduce the amount of contaminants reaching the first chamber 15 from the second chamber 16. The cooling region 59 of the heat exchanger 60 is in thermal communication with the portion 52 of the wall 80 of the channel 52 via the thermal conductor 61. The walls 80 of the channels 51 may be formed of a thermally conductive material such that the cooling power provided by the heat exchanger 60 via the dedicated heat conductor 61 and the mount 63 is spread over the walls 80 of the channels 51. This enables the portion of the wall 80 that is not in direct contact with the mount 63 to be cooled by the cooling system 50. The walls 80 of the channel 51 may be formed of metal, such as steel, aluminum, and/or titanium. The mounting member 38 may be formed of metal, such as steel. The flow of cleaning fluid 56 through the cooling portion 52 of the wall 80 of the channel 51 is cooled by the cooling portion of the wall 80 of the channel 51. It may be preferable that a lower portion of the wall 80 of the channel 51 (i.e., the portion of the wall of the channel below the cleaning fluid inlet 55 of the wall of the channel) is cooled. This is because cooling the cleaning fluid increases the density of the cleaning fluid, and thus cooling the cleaning fluid below the cleaning fluid inlet 55 increases the proportion of the cleaning fluid flow that travels toward the second chamber 16.
As described above, the lithographic apparatus may comprise a cooling apparatus 54, the cooling apparatus 54 being configured to cool one or more areas of the substrate W, for example an area near an exposure target area of the substrate W. A portion of the cooling apparatus 54 may be cooled to cool a flow of the cleaning fluid 56 in the vicinity of the cooling apparatus 54. As described above, cooling the cleaning fluid below the cleaning fluid inlet of the wall 80 of the channel 51 may increase the proportion of the cleaning fluid flow travelling towards the second chamber 16, thereby reducing the amount of contaminants reaching the first chamber 15 from the second chamber 16. The cooling system 50 may be configured to cool a portion of the cooling apparatus 54. For example, the cooling region 59 of the heat exchanger 60 may be in thermal communication with a portion of the cooling device 54 via a dedicated thermal conductor, such as a heat pipe (not shown).
If the cleaning fluid curtain 53 is overcooled, overcooling of the substrate W may occur, which may result in overlay errors during lithographic exposure. By not cooling a portion of the walls 80 of the channels 51, excessive cooling of the substrate W may be reduced and/or avoided. The portion 64 of the wall 80 of the channel 51 above the cleaning fluid inlet 55 may not be cooled and may be heated. The lithographic apparatus may further comprise a heating system 68, the heating system 68 being configured to heat a portion 64 of a wall 80 of the channel 51. For example, the hot region 66 of the heat exchanger 65 may be in thermal communication with the portion 64 of the wall 80 of the channel 51 via a dedicated thermal conductor 67 (e.g., one or more heat pipes). Alternatively, the hot side 69 of the heat exchanger 60 of the cooling system 50 may be used to provide thermal energy to the portion 64 of the wall 80 of the channel 51. A portion 64 of the wall 80 of the heating channel 51 above the cleaning fluid inlet 55 may advantageously reduce the amount of contamination from the second chamber 16 to the first chamber 15. This is because the cleaning fluid 56 above the cleaning fluid inlet 55 will acquire thermal energy from the heated portion 64 of the wall 80 of the channel 51 and experience thermal expansion. Thermal expansion of the cleaning fluid 56 over the cleaning fluid inlet 55 causes an increase in the flow of the cleaning fluid 56 towards the second chamber 16. Increasing the proportion of the flow of cleaning fluid travelling towards the second chamber 16 may advantageously reduce the amount of contaminants reaching the first chamber 15 from the second chamber 16.
Cooling the walls 80 of the channels 51 before the cleaning fluid reaches the channels 51, instead of cooling only the cleaning fluid 56, advantageously reduces heat transfer from the cleaning fluid 56 to the substrate W, because the cleaning fluid 56 is cooled by the walls 80 of the channels 51, as well as the rise in temperature of the cleaning fluid 56 as the cleaning fluid 56 travels from the heat exchanger 49 to the channels 31, calculates when the cleaning fluid 56 is cooled by the walls 80 of the channels 51. The heat exchanger 49 configured to pre-cool the cleaning fluid is optional. The walls 80 of the cooling channel 51 advantageously increase the mass flow of the purging fluid 56 to the second chamber 16, as decreasing the temperature of the purging fluid 56 in the channel 51 increases the density of the purging fluid 56 in the channel 51. The walls 80 of the cooling channel 51 advantageously reduce the diffusion coefficient of the cleaning fluid for diffusion of contaminants from the second chamber 16 to the first chamber 15. This is because, although decreasing the temperature of the cleaning fluid 56 increases the density of the cleaning fluid, the cleaning fluid diffusion coefficient for contaminants scales more strongly with the temperature of the cleaning fluid (as compared to the density with the cleaning fluid). Thus, as the temperature of the cleaning fluid 56 in the fluid curtain 53 is reduced by the wall 80 of the channel 51, the diffusion coefficient of the cleaning fluid 56 for contaminants is reduced.
The walls 80 of the cooling channel 51 advantageously reduce the dependence of the cooling system 50 on the flow of the cleaning fluid 56 provided to the channel 51, since the cleaning fluid is cooled when it reaches the channel 51, rather than only in the conduit 58 on its way to the channel 51. The cooling system 50 may achieve a greater range of cleaning fluid flow rates. A membrane (not shown) may be provided in the embodiment of the channel shown in fig. 4. The lower dependence on the flow rate of the cleaning fluid 56 allows the channel 51 comprising the cooling system 50 to be adapted both to the case where a film is present in the channel 51 and to the case where a film is not present in the channel 51.
Cooling the walls 80 of the channels 51 also advantageously reduces variations in lithographic errors between different lithographic apparatus caused by heat transfer from the cleaning fluid 56 to the substrate W. This is because the cleaning fluid 56 is cooled by the walls 80 of the channels 51, so that any effect of heat transfer to the cleaning fluid 56 that is dependent on the lithographic apparatus is reduced as the cleaning fluid travels from the heat exchanger 60 to the channels 51. In other words, the thermal history of the cleaning fluid 56 is less important because once the cleaning fluid 56 reaches the channel 51, the cleaning fluid 56 is cooled by the walls 80 of the channel 51. For example, variations in lithographic error between different lithographic apparatus may be the result of manufacturing tolerances that result in differences between the same model of lithographic apparatus.
Cooling the walls 80 of the channels 51 may advantageously reduce the flow of the cleaning fluid 56 required to achieve the desired level of contaminant suppression. For example, cooling the walls 80 of the channels 51 may reduce the flow of the cleaning fluid 56 required to achieve the desired level of contaminant suppression by about 10%. Reducing the required flow of cleaning fluid 56 advantageously reduces the vacuum requirements of first chamber 15 and/or second chamber 16, thereby reducing the operating cost of the lithographic apparatus.
Fig. 5 schematically shows a view from above of the opening of a known channel 70. The wall 81 of the channel 70 comprises a cleaning fluid inlet 71, which cleaning fluid inlet 71 is continuous around the periphery 72 of the channel 70 such that the flow of cleaning fluid (not shown) is evenly distributed along the periphery 72 of the channel 70. However, due to the shape of the perimeter 72 of the channel 70, the flow of cleaning fluid within the channel 70 may be non-uniform. The shape of the opening of the channel 70 may be considered as a combination of a central portion 73 and two end portions 74a-b at opposite ends of the central portion 73. In the example of fig. 5, the central portion 73 is generally rectangular and the end portions 74a-b are generally semi-circular. In fact, the central portion 73 of the channel 70 may be curved, so the channel may have a shape more like a kidney or banana than shown in the example of fig. 5. In general, the central portion 73 and the end portions 74a-b may have shapes that are different from the shapes shown in the example of FIG. 5.
The central portion 73 of the channel 70 is provided with a cleaning fluid through a first cleaning fluid inlet section 75 and a second cleaning fluid inlet section 76. The total length of the cleaning fluid inlet providing cleaning fluid to the central portion 73 is equal to the length of the first cleaning fluid inlet section 75 and the length of the second cleaning fluid inlet section 76. The first end portion 74a of the channel 70 is provided with a cleaning fluid through a third cleaning fluid inlet section 77. The total length of the cleaning fluid inlet providing cleaning fluid to the first end portion 74a is equal to the length of the third cleaning fluid inlet section 77. The second end portion 74b of the channel 70 is provided with cleaning fluid through a fourth cleaning fluid inlet section 78. The total length of the cleaning fluid inlet providing cleaning fluid to the second end portion 74b is equal to the length of the fourth cleaning fluid inlet section 78.
As can be seen in fig. 5, the central portion 73 covers a larger cross-sectional area of the channel 70 than each of the end portions 74a-b. In the known channel 70, the flow of cleaning fluid is evenly distributed across the cleaning fluid inlet 71. However, different portions of the purge fluid inlet provide purge fluid flow to different sized cross-sectional areas 73, 74a-b of the channel 70. That is, the ratio of the size of the cross-sectional area of the channel to which the cleaning fluid is provided by a section of the cleaning fluid inlet to the length of the section of the cleaning fluid inlet varies around the perimeter 72 of the channel 70. Variations in the ratio of the channel cross-sectional area to the cleaning fluid inlet length may result in uneven flow of cleaning fluid within the channel 70. In the example of fig. 5, the ratio of the cross-sectional area of the central portion 73 of the channel 70 to the lengths 75, 76 of the cleaning fluid inlet 71 providing cleaning fluid to the central portion 73 is about twice the ratio of the cross-sectional area of the end portions 74a, 74b to the lengths 77, 78 of the cleaning fluid inlet 71 providing cleaning fluid to the end portions 74a, 74 b. The difference in the ratio of the cross-sectional area of the channel between the different sections of the cleaning fluid inlet 71 to the length of the cleaning fluid inlet may result in a non-uniform flow of cleaning fluid through the channel 70. Uneven cleaning fluid flow within the channel may not suppress contamination as well as more uniform cleaning fluid flow within the channel.
Fig. 6 schematically shows a top view of the opening of a channel 90 according to an embodiment of the invention, which channel 90 comprises a cleaning fluid inlet 91 with a restrictor 92. The restrictor 92 is configured to allow different sections of the cleaning fluid inlet 91 to provide different flows of cleaning fluid to the channel 90. In the example of fig. 6, the flow restrictor 92 comprises a baffle. The baffle 92 is configured to divide the cleaning fluid inlet 91 into separate/discrete segments 93a-d that are capable of providing different flows of cleaning fluid to the channel (e.g., to different cross-sectional areas of the channel 90). The first and second sections 93a-b of the cleaning fluid inlet 91 provide cleaning fluid to the central region 94a of the channel 90. The third section 93c of the cleaning fluid inlet 91 provides cleaning fluid to the end region 94b of the channel 90. The fourth section 93d of the cleaning fluid inlet 91 provides cleaning fluid to the other end region 94c of the channel 90.
The baffle 92 divides the cleaning fluid inlet into different sections 93a-d so that different flow rates of cleaning fluid can be provided to different cross-sectional areas 94a-c of the channel 90 through the different sections 93a-d of the cleaning fluid inlet 91. The flow rate of the cleaning fluid provided to the different sections 93a-d of the cleaning fluid inlet 91 may vary between the different sections 93a-d of the cleaning fluid inlet 91 to correspond to the size of the cross-sectional area 94a-c to which each section 93a-d of the cleaning fluid inlet 91 of the channel 90 provides cleaning fluid. For example, the flow rate of the cleaning fluid provided to the different sections 93a-d of the cleaning fluid inlet 91 may depend at least in part on the ratio of the size of the cross-sectional areas 94a-c of the channel 90 to the total length of the cleaning fluid inlet sections 93a-d providing cleaning fluid to the cross-sectional areas of the channel. Each segment 93a-d of the cleaning fluid inlet 91 may, for example, include a mass flow controller (not shown). The mass flow controller may be configured to control the flow of the cleaning fluid supplied through the segments 93a-d of the cleaning fluid inlet 90.
In the example of fig. 6, the channel 90 has a kidney-shaped shape. However, in a manner similar to that discussed above with respect to FIG. 5, the channel 90 may be approximated as having a central portion 94a and two end portions 94b-c. In the example of fig. 6, the central portion 94a and the end portions 94b-c are curved, wherein the radius of curvature of the central portion 94a is smaller than the radius of curvature of the end portions 94b-c. In this example, the ratio of the cross-sectional area of the central portion 94a of the channel 90 to the total length of the cleaning fluid inlet sections 93a-b providing cleaning fluid to the central portion 94a is approximately twice the ratio of the cross-sectional area of the end portions 94b-c to the length of the cleaning fluid inlet sections 93c-d providing cleaning fluid to the end portions 94b-c. In the example of fig. 6, providing twice the flow of cleaning fluid to the first and second sections 93a-b of the cleaning fluid inlet 91 as to the third and fourth 93c-d of the cleaning fluid inlet 91 may reduce the non-uniformity of the cleaning fluid flow within the channel 90, which may advantageously reduce the amount of contamination from the second chamber (not shown) to the first chamber (not shown).
The cross-sectional shape of the channel may be different from that shown in fig. 5 and 6. Those skilled in the art will appreciate that channels having different cross-sectional shapes may be represented as any desired combination of cross-sectional areas. In general, the ratio of the size of the cross-sectional area of the channel to the total length of the cleaning fluid inlet section providing cleaning fluid to that cross-sectional area may be determined for different cross-sectional areas of the channel, and the flow rate of the cleaning fluid provided to the different cross-sectional areas via the different sections of the cleaning fluid inlet may be determined therefrom. A computational fluid dynamics model, for example, may be used to determine the flow rate of the cleaning fluid that needs to be provided to the different cross-sectional areas via the different sections of the cleaning fluid inlet in order to reduce flow non-uniformities within the channel.
In the example of fig. 6, a baffle 92 is provided to divide the cleaning fluid inlet into four segments 93a-d, wherein some of the segments receive different flows of cleaning fluid. In the example of FIG. 6, the cleaning fluid is provided to each segment of the cleaning fluid inlets 93a-d via different channels 95a-d such that the flow rate of the cleaning fluid provided to each segment of the cleaning fluid inlets 93a-d may be different between different segments of the cleaning fluid inlets 93 a-d. A greater or lesser number of baffles 92 may be provided to divide the cleaning fluid inlet 91 into a greater or lesser number of segments 93a-d, which segments 93a-d are provided with cleaning fluid through a greater or lesser number of passages 95 a-d. It may be preferable to provide more baffles 92 to divide the cleaning fluid inlet 91 into a greater number of segments 93a-d so that the segments are smaller and the flow provided to the different segments 93a-d of the cleaning fluid inlet 91 may vary more finely around the periphery of the channel.
Fig. 7 schematically illustrates a cross-sectional view of a segment of a cleaning fluid inlet 100 including a flow restrictor 101, in accordance with an embodiment of the present invention. In the example of fig. 7, the direction of the purge fluid flow is into the page. The restrictor 101 is configured to allow different sections 103a-b of the cleaning fluid inlet 100 to provide different flows of cleaning fluid to the channel (not shown). Restrictor 101 includes varying purge fluid inlet opening sizes 102a-b. The first section 103a of the cleaning fluid inlet 100 has a first opening size 102a and the second section 103b of the cleaning fluid inlet 100 has a second opening size 102b. The first opening size 102a of the cleaning fluid inlet 100 is larger than the second opening size 102b of the cleaning fluid inlet 100, which means that a larger flow of cleaning fluid (than the flow of cleaning fluid provided to the second section 103b of the cleaning fluid inlet 100) can be provided to the channel through the first section 103a of the cleaning fluid inlet.
The cleaning fluid inlet 100 may be uniformly and isobarically provided with cleaning fluid throughout the length of the cleaning fluid inlet 100. However, the varying opening size of the cleaning fluid inlet 100 results in different sections 103a-b of the cleaning fluid inlet 100 providing different flow rates of cleaning fluid to different cross-sectional areas of the channel. In practice, it may be difficult to provide a flow of cleaning fluid with equal pressure over the entire length of the cleaning fluid inlet 100 due to non-zero flow resistance within the cleaning fluid inlet. For example, the cleaning fluid may be provided to the cleaning fluid inlet 100 of the wall 104 of the channel via a conduit that injects the cleaning fluid into only a small section of the cleaning fluid inlet. The cleaning fluid may exit the conduit into the cleaning fluid inlet and then spread along the cleaning fluid inlet and flow into the channel. In this example, the pressure of the cleaning fluid in the cleaning fluid inlet is greater near the conduit and less away from the conduit. The variation in the opening dimensions 102a-b of the cleaning fluid inlet may be selected so as to improve the equalization of the pressure of the cleaning fluid in the cleaning fluid inlet.
The flow rate of the cleaning fluid provided to the channels by the different sections 103a-d of the cleaning fluid inlet 100 may depend at least in part on the ratio of the size of the cross-sectional area of the channels to the total length of the cleaning fluid inlet sections 103a-d providing cleaning fluid to the cross-sectional area of the channels. For example, the ratio of the size of the cross-sectional area of the channel provided with the cleaning fluid provided by the first section 103a of the cleaning fluid inlet to the length of the first section 103a of the cleaning fluid inlet may be about twice the ratio of the size of the cross-sectional area of the channel provided with the cleaning fluid provided by the second section 103b of the cleaning fluid inlet to the length of the second section 103b of the cleaning fluid inlet. In this example, providing the first section 103a of the cleaning fluid inlet 100 with an opening size 102a that is approximately twice the opening size 102b of the second section 103b of the cleaning fluid inlet 100 may result in approximately twice the flow rate of the cleaning fluid provided to the first section 103a of the cleaning fluid inlet than the flow rate of the cleaning fluid provided to the second section 103b of the cleaning fluid inlet, thereby achieving a more uniform flow of the cleaning fluid within the channel. For example, the opening size 102a of the first section of the cleaning fluid inlet 103a may be about 0.5mm, while the opening size 102b of the second section of the cleaning fluid inlet 103b may be about 0.25mm.
The baffles may be used in combination with varying cleaning fluid inlet opening sizes. The use of varying opening sizes of the cleaning fluid inlet advantageously allows the flow rate of the cleaning fluid to vary more continuously around the cleaning fluid inlet of the channel than if baffles were used. For example, the opening size of the cleaning fluid inlet may be continuously varied around the periphery of the channel to achieve a desired distribution of cleaning fluid flow around the periphery of the channel. Reducing non-uniformity of the flow of cleaning fluid within the channel advantageously increases the suppression of contaminants from the second chamber to the first chamber. Reducing non-uniformity in the flow of the cleaning fluid within the channels may allow for a lower total flow of cleaning fluid to be used.
Fig. 8 schematically shows a cross-sectional view from the side of the known channel 110. The known channel 110 comprises a cleaning fluid inlet 111 extending along the periphery of the channel 110. The perimeter of the channel 110 is defined by a wall 116. The injection angle 114 of the cleaning fluid through the cleaning fluid inlet 111 may be defined as the angle between a line 115 bisecting the cleaning fluid inlet 111 and the optical axis 113 of the lithographic apparatus. The known channel 110 comprises a substantially vertical injection angle 114.
Fig. 9 schematically illustrates a cross-sectional view from the side of a channel 120 comprising an angled cleaning fluid inlet 121, according to an embodiment of the invention. An angled cleaning fluid inlet 121 extends along the perimeter of the channel 120. The injection angle 122 of the cleaning fluid through the angled cleaning fluid inlet 121 may be defined as the angle between a line 136 bisecting the angled cleaning fluid inlet 121 and the optical axis 124 of the lithographic apparatus. Providing a non-perpendicular injection angle advantageously increases the momentum of the flow of cleaning fluid traveling toward the second chamber. The increased momentum of the cleaning fluid flow traveling to the second chamber enhances the containment of the contaminants. Theoretically, the injection angle 122 may be matched to an angle 125 between a wall 126 of the channel 120 and an optical axis 124 of the lithographic apparatus, in order to give the cleaning fluid as much momentum in the direction of the second chamber (not shown) as possible, thus enhancing the suppression of contaminants travelling towards the first chamber (not shown). In the example of fig. 9, the angle 125 (which may be referred to as a channel wall angle) between the wall 125 of the channel 120 and the optical axis 124 of the lithographic apparatus is about 55 °, and therefore the injection angle 122 may preferably be as close to 55 ° as possible. However, machining limitations in manufacturing the walls 126 of the channel 120 including the angled cleaning fluid inlet 121 may limit the extent to which the injection angle 122 substantially matches the channel wall angle 125. For example, due to tooling limitations, the injection angle 122 may be about 43 ° instead of about 55 °. The difference between the channel wall angle 125 and the injection angle 122 may be between about 1 ° and about 15 °. The injection angle 122 may vary along the perimeter of the channel 120. The walls 126 of the channel 120 and the walls of the angled cleaning fluid inlet 121 may be formed of metal, such as steel, aluminum, and/or titanium.
Having an angled cleaning fluid inlet 121 allows the cleaning fluid to have a greater momentum in the direction of the second chamber (not shown) as it enters the channel 120 via the angled cleaning fluid inlet 121. Increasing the momentum of the cleaning fluid in the direction of the second chamber advantageously increases the proportion of the cleaning fluid flowing to the second chamber, which reduces the amount of contamination from the second chamber to the first chamber. However, having an angled cleaning fluid inlet 121 may reduce the effective inhibition length of the fluid curtain in the channel 120 as compared to a cleaning fluid inlet (e.g., the cleaning fluid inlet of the channel shown in fig. 8) in a known channel that is positioned at the same height along the wall 126 of the channel (e.g., at about half the height of the wall of the channel). The effective inhibition length of the fluid curtain in the channel 120 may be understood as the distance across which the cleaning fluid flows to the second chamber. Accordingly, it may be preferable to increase the height 128 of the angled cleaning fluid inlet 121 along the wall 126 of the channel 120, thereby maintaining or increasing the effective inhibited length of the fluid curtain. The height 128 of the cleaning fluid inlet 121 may be defined relative to the substrate table WT as the distance between the lower wall 127 of the cleaning fluid inlet and the upper surface of the substrate table WT. In known channels (e.g., the channel shown in fig. 8), the purge fluid inlet may be about 15mm in height. The height 128 of the angled cleaning fluid inlet 121 may be greater than 15mm, for example, between about 20mm and about 30 mm. The height of the angled cleaning fluid inlet 121 may vary along the perimeter of the channel 120.
The inner walls 123, 127 of the cleaning fluid inlet 121 may be curved. The upper inner wall 123 of the cleaning fluid inlet may be linear, while the lower inner wall 127 of the cleaning fluid inlet 121 may be curved. Alternatively, the upper inner wall 123 of the cleaning fluid inlet may be curved/curved, while the lower inner wall 127 of the cleaning fluid inlet may be linear. As another alternative, both the upper inner wall 123 of the cleaning fluid inlet and the lower inner wall 127 of the cleaning fluid inlet may be curved. The inner walls 123, 127 of the cleaning fluid inlet 121 may be curved such that there is a smooth transition from the curved inner walls of the cleaning fluid inlet to the walls 126 of the channel 120. In the example of fig. 9, the lower inner wall 127 of the cleaning fluid inlet is curved such that there is a smooth transition from the lower inner wall 127 of the cleaning fluid inlet to the wall 126 of the channel 120. A smooth transition from the lower inner wall 127 of the cleaning fluid inlet 121 to the channel wall 127 may reduce the separation of the upward flow of cleaning fluid to the first chamber and the downward flow to the second chamber. That is, a greater proportion of the cleaning fluid flow may exit the angled cleaning fluid inlet 121 and travel toward the second chamber, which in turn may advantageously reduce the amount of contamination from the second chamber to the first chamber.
The inner walls 123, 127 of the cleaning fluid inlet 121 may be curved such that the cleaning fluid inlet defines a converging flow path for the cleaning fluid. In the example of fig. 9, the lower inner wall 127 of the cleaning fluid inlet 121 is curved such that the cleaning fluid inlet 121 defines a converging flow path for the cleaning fluid. That is, as it travels toward the channel 120 via the cleaning fluid inlet 121, the volume through which the cleaning fluid flows decreases. The flow path of the cleaning fluid may be said to diverge as it exits the cleaning fluid inlet 121 into the channel 120. The converging flow path formed by the one or more curved inner walls 127 of the cleaning fluid inlet 121 may function like a converging flow path of a Laval nozzle. The converging flow path of the cleaning fluid defined by the curved inner wall of the cleaning fluid inlet may facilitate acceleration (e.g., up to supersonic) of the cleaning fluid toward the second chamber, which in turn may advantageously reduce the amount of contamination from the second chamber to the first chamber. The inner walls 126, 127 of the cleaning fluid inlet 121 may be curved/curved such that the opening size 130 of the cleaning fluid inlet is narrowest at or before the end of the cleaning fluid inlet. The angled cleaning fluid inlet 121 is configured such that the narrowest opening dimension 130 of the cleaning fluid inlet is at or before the end of the cleaning fluid inlet (rather than at the edge of the cleaning fluid inlet as shown in fig. 9), which may further facilitate acceleration of the cleaning fluid toward the second chamber, as the inner wall of the cleaning fluid inlet extending beyond the narrowest portion of the cleaning fluid inlet 121 toward the channel 120 may define a diverging portion of the cleaning fluid flow path in the cleaning fluid inlet. The selection of the radius of curvature of the curved inner wall 127 of the cleaning fluid inlet 121 may be determined, at least in part, by the size of the channel wall angle 125 and the desired opening dimension 130 of the cleaning fluid inlet. A membrane (not shown) may be provided in the embodiment of the channel shown in fig. 9.
Fig. 10 schematically shows a perspective view of a cross section of a channel 131 comprising an angled cleaning fluid inlet 132 according to an embodiment of the invention. The angled cleaning fluid inlet 132 is supplied with cleaning fluid through a cleaning fluid reservoir 133. The cleaning fluid reservoir 133 extends circumferentially around the channel 131. The volume of the cleaning fluid reservoir 133 may be large enough to equalize the pressure of the cleaning fluid so that the cleaning fluid is evenly distributed over the angled cleaning fluid inlet 132. If there is insufficient room in the lithographic apparatus for the cleaning fluid reservoir 133 to be large enough to equalize the cleaning fluid pressure within the cleaning fluid inlet 132, the opening size of the cleaning fluid inlet may be varied to achieve equalization of the cleaning fluid pressure within the cleaning fluid inlet, for example as discussed above with respect to FIG. 7. The lower inner wall 134 of the angled cleaning fluid inlet 132 is curved to form a smooth transition with the wall 135 of the channel 131. The walls 135 of the channels 131 may be formed of metal, such as steel, aluminum, and/or titanium.
Fig. 11 schematically illustrates the known channel 110 shown in fig. 8, wherein a visible flow of cleaning fluid 140 exits the cleaning fluid inlet 111. As can be seen in fig. 11, at least a portion of the cleaning fluid 140 is recirculated below the cleaning fluid inlet 111. Some of the cleaning fluid flow may be recirculated in a similar manner over a cleaning fluid inlet (not shown). Recirculation occurs because the cleaning fluid flow separates after exiting the cleaning fluid inlet 111 and the pressure within the channel 110 increases as it moves down the channel wall 141 below the cleaning fluid inlet 111. That is, the static pressure of the purge fluid flow at the purge fluid inlet 111 is lower than the stagnation pressure of the purge fluid flow in the channel 110. The recirculation of the cleaning fluid 140 may cause contaminants to be pushed up along the channel wall 141 toward the first chamber (not shown) by the recirculation flow of the cleaning fluid 140. In the example of fig. 11, the cleaning fluid inlet 111 is shown to be located at about half of the channel wall 141. The cleaning fluid inlet 111 may be located at a lesser or greater elevation of the channel wall 141. For example, the cleaning fluid inlet 111 may be located approximately one third up the channel wall 141 from the bottom of the channel wall, or approximately one quarter up the channel wall 141 from the bottom of the channel wall.
Fig. 12 schematically illustrates a channel 150 comprising a plurality of cleaning fluid inlets 151a-b according to an embodiment of the invention. The wall 152 of the channel 150 includes a first cleaning fluid inlet 151a, which first cleaning fluid inlet 151a may be located, for example, along the wall 152 of the channel 150 at substantially the same height as the cleaning fluid inlet shown in fig. 11 (e.g., along about half of the wall 152 of the channel 150). As in the case of the channel shown in fig. 11, the first cleaning fluid inlet 151a may be located at a greater or lesser elevation along the channel wall 152, for example, may be located at about one third of the way along the channel wall 152 from the bottom of the channel wall, or at about one quarter of the way along the channel wall 152 from the bottom of the channel wall. The second cleaning fluid inlet 151b is disposed closer to the substrate W than the first cleaning fluid inlet 151 a. First cleaning fluid flow 153a is shown exiting first cleaning fluid inlet 151a, and second cleaning fluid flow 153b is shown exiting second cleaning fluid inlet 151b. The flow rate of the cleaning fluid provided through the second cleaning fluid inlet 151b may be smaller than the flow rate of the cleaning fluid provided through the first cleaning fluid inlet 151 a. A second cleaning fluid inlet 151b is provided closer to the substrate W than the first cleaning fluid inlet 151a, which provides a region of increased pressure below the first cleaning fluid inlet 151 a. Thus, as it travels down the channel wall 152 below the second cleaning fluid inlet 151b, the pressure within the channel 150 decreases rather than increases. This reversal of the pressure gradient results in a reduction in recirculation of the cleaning fluid 153a-b within the channel 150, which advantageously reduces the amount of contamination traveling along the channel wall 152 from the second chamber to the first chamber. In other words, the flow of cleaning fluid exiting the second cleaning fluid inlet 151b defines a velocity vector in the region of the second cleaning fluid inlet 151b that does not allow significant recirculation to occur in the region of the second cleaning fluid inlet 151b.
The opening size 154 of the second cleaning fluid inlet 151b may be between about 0.2mm and about 5mm, for example, about 1 millimeter. The first cleaning fluid inlet 151a may have a height 155 of between about 10mm and about 40mm, for example about 20 mm, relative to the substrate table WT. The height of the second cleaning fluid inlet 156 relative to the substrate table WT may be between about 6mm and about 30mm, for example about 12 mm. The height of the second cleaning fluid inlet 156 may be between about 25% and about 75% of the height of the first cleaning fluid inlet 155.
The flow rate of the cleaning fluid 153b provided through the second cleaning fluid inlet 151b may depend at least in part on the flow rate of the cleaning fluid flowing from the channel 150 to the second chamber (not shown) when substantially no cleaning fluid flow is provided through the second cleaning fluid inlet 151 b. Preferably, the flow rate of the cleaning fluid provided through the second cleaning fluid inlet 151b is between about 50% and about 200% of the flow rate of the cleaning fluid flowing from the channel 150 to the second chamber when substantially no cleaning fluid flow is provided through the second cleaning fluid inlet 151 b. In one example, when substantially no cleaning fluid flow is provided through the second cleaning fluid inlet 151b, about 300mbar is provided through the first cleaning fluid inlet 151a -1 The flow rate of the cleaning fluid 153a from the channel to the second chamber is about 40mbar -1 . In this example, about 20 mbars is preferably provided through the second cleaning fluid inlet 151b -1 About 80 mbars -1 To reduce recirculation of the cleaning fluid within the channel 150. The walls 152 of the channel 150 may be formed of metal, such as steel, aluminum, and/or titanium.
A controller (not shown) may be provided, which is configured to control the flow rate of the cleaning fluid supplied through the first cleaning fluid inlet 151a and the flow rate of the cleaning fluid supplied through the second cleaning fluid inlet 151 b. The controller may be configured to control the flow rate of the cleaning fluid provided through the second cleaning fluid inlet 151b based on the flow rate of the cleaning fluid flowing from the channel 150 to the second chamber when substantially no cleaning fluid flow is provided through the second cleaning fluid inlet 151 b. The controller may be configured to provide a flow rate of the cleaning fluid through the second cleaning fluid inlet 151b that is between about 50% and about 200% of the flow rate of the cleaning fluid flowing from the channel 150 to the second chamber when substantially no cleaning fluid flow is provided through the second cleaning fluid inlet 152 b.
The skilled person will appreciate that the different features of the different embodiments may be combined in any desired combination. For example, the channel may include two or more cleaning fluid inlets at different heights along the channel wall, and the one or more cleaning fluid inlets may be angled cleaning fluid inlets, and/or the one or more cleaning fluid inlets may include a restrictor. As another example, fig. 13 schematically illustrates a perspective view of a channel 200 comprising first and second cleaning fluid inlets 201, 202 and a cooling system 203, according to an embodiment of the invention. The first cleaning fluid inlet 201 is angled. In the example of fig. 13, the second cleaning fluid inlet 202 is not angled and is located below the first cleaning fluid inlet 201. Alternatively, the second cleaning fluid inlet 202 may be angled in a similar manner as the first cleaning fluid inlet 201. If the second cleaning fluid inlet 202 is angled, it may be preferable to position the second cleaning fluid inlet 202 at a greater height along the wall 205 of the channel 200 than if the second cleaning fluid inlet 202 is not angled. The second cleaning fluid inlet, which need not be angled, provides a region of increased pressure below the first cleaning fluid inlet 201. The channel 200 shown in fig. 13 is part of a lithographic apparatus that further comprises a cooling apparatus 204. The components of the cooling device 204 may be cooled as discussed above with respect to fig. 4.
The cleaning fluid may be hydrogen. Other cleaning fluids may be used. For example, the purge fluid may include nitrogen, helium, and/or argon, or any combination thereof. The channels have been shown as having a generally conical cross section. However, the channels may take other forms. For example, the channels may have a generally rectangular cross-section or a generally square cross-section. The cooling system may include one or more heat pipes. The heat pipes may be connected in series or in parallel.
The term "EUV radiation" may be considered to include electromagnetic radiation having a wavelength in the range of 4-20nm, for example in the range of 13-14 nm. EUV radiation may have a wavelength of less than 10nm, for example in the range of 4-10nm, for example 6.7nm or 6.8nm.
Although fig. 1 depicts the radiation source SO as a laser produced plasma LPP source, any suitable source may be used to generate EUV radiation. For example, EUV emitting plasma may be generated by converting a fuel (e.g., tin) into a plasma state using an electrical discharge. This type of radiation source is known as a discharge-generated plasma (DPP) source. The discharge may be generated by a power supply, which may form part of the radiation source, or may be a separate entity connected to the radiation source SO by an electrical connection.
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. Possible other applications include 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.
While specific embodiments of the invention have been described above, it should be appreciated that the invention may be practiced otherwise than as described. The above description is intended to be illustrative, and not restrictive. It will therefore be apparent to those 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.

Claims (35)

1. A lithographic apparatus comprising:
a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate;
a second chamber comprising a substrate table configured to hold a substrate;
a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of a cleaning fluid, a perimeter of the channel defined by a wall; and
A cooling system configured to cool the wall of the channel;
wherein a cleaning fluid inlet for injecting a cleaning fluid is provided to the wall of the channel, and a portion of the wall located below the cleaning fluid inlet is cooled;
wherein the lithographic apparatus further comprises a heating system configured to heat a portion of the wall of the channel above a cleaning fluid inlet of the wall of the channel.
2. The lithographic apparatus of claim 1, wherein the cooling system comprises a dedicated thermal conductor in thermal communication with the wall of the channel.
3. The lithographic apparatus of claim 2, wherein the dedicated thermal conductor comprises a heat pipe.
4. A lithographic apparatus according to claim 3, wherein the dedicated thermal conductor comprises two or more heat pipes connected in parallel.
5. The lithographic apparatus of any of claims 2 to 4, wherein the cooling system further comprises a heat exchanger in thermal communication with the dedicated thermal conductor.
6. The lithographic apparatus of any of claims 2 to 4, wherein the cooling system is configured to cool the cleaning fluid before flowing to the channel via a conduit.
7. The lithographic apparatus of any of claims 2 to 4, wherein the cooling system comprises a mount configured to provide a thermally conductive path between the dedicated thermal conductor and the wall of the channel.
8. The lithographic apparatus of claim 7, wherein the mount comprises an attachment structure configured to enable removal and reattachment of the cooling system to the wall of the channel.
9. The lithographic apparatus of claim 8, wherein the attachment structure comprises threads for receiving a bolt.
10. The lithographic apparatus of any one of claims 1 to 4, wherein the cooling system further comprises a controller and a temperature sensor, the temperature sensor being configured to measure the temperature of the wall of the channel and output a signal indicative of the temperature of the wall of the channel, the controller being configured to receive a signal from the temperature sensor and to adjust the cooling provided by the cooling system based on the signal received from the temperature sensor.
11. The lithographic apparatus of claim 10, wherein the controller is a proportional-integral-derivative controller.
12. The lithographic apparatus of any of claims 1 to 4, wherein the lithographic apparatus further comprises a cooling apparatus configured to cool a region of the substrate, and wherein the cooling system is configured to cool a portion of the cooling apparatus.
13. A lithographic apparatus comprising:
a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate;
a second chamber comprising a substrate table configured to hold a substrate;
a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of a cleaning fluid, a perimeter of the channel defined by a wall, the wall of the channel including a cleaning fluid inlet;
wherein the purging fluid inlet includes a restrictor configured to allow different sections of the purging fluid inlet to provide different flows of purging fluid to the channel;
wherein a portion of the wall of the channel below the cleaning fluid inlet is cooled and a portion of the wall of the channel above the cleaning fluid inlet of the wall of the channel is heated.
14. The lithographic apparatus of claim 13, wherein the flow restrictor comprises a baffle configured to divide the cleaning fluid inlet into the different segments.
15. The lithographic apparatus of claim 13 or 14, wherein the flow restrictor comprises a varying cleaning fluid inlet opening size such that the different sections of the cleaning fluid inlet have different opening sizes.
16. A lithographic apparatus comprising:
a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate;
a second chamber comprising a substrate table configured to hold a substrate;
a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of cleaning fluid, the perimeter of the channel defined by a wall, the wall of the channel including an angled cleaning fluid inlet, wherein a portion of the wall of the channel below the cleaning fluid inlet is cooled and a portion of the wall of the channel above the cleaning fluid inlet of the wall of the channel is heated;
Wherein the inner wall of the angled cleaning fluid inlet is curved.
17. The lithographic apparatus of claim 16, wherein the inner wall of the cleaning fluid inlet is curved such that there is a smooth transition from the inner wall of the cleaning fluid inlet to the wall of the channel.
18. The lithographic apparatus of claim 16 or 17, wherein the inner wall of the cleaning fluid inlet is curved such that the cleaning fluid inlet defines a converging flow path for cleaning fluid.
19. The lithographic apparatus of claim 16 or 17, wherein the inner wall of the cleaning fluid inlet is curved such that an opening size of the cleaning fluid inlet is narrowest at or before an end of the cleaning fluid inlet.
20. The lithographic apparatus of claim 16 or 17, wherein a distance between a lower wall of the cleaning fluid inlet and the substrate table is greater than 15mm.
21. A lithographic apparatus comprising:
a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate;
a second chamber comprising a substrate table configured to hold a substrate;
A channel extending between the first chamber and the second chamber, the channel configured to receive a flow of cleaning fluid, a perimeter of the channel defined by a wall, the wall of the channel comprising a first cleaning fluid inlet and a second cleaning fluid inlet, the second cleaning fluid inlet being positioned closer to the substrate than the first cleaning fluid inlet, wherein a portion of the wall of the channel below the cleaning fluid inlet is cooled and a portion of the wall of the channel above the cleaning fluid inlet of the wall of the channel is heated; and
a controller configured to control a flow rate of the cleaning fluid provided through the first cleaning fluid inlet and a flow rate of the cleaning fluid provided through the second cleaning fluid inlet, wherein the controller is configured to control the flow rate of the cleaning fluid provided through the second cleaning fluid inlet based on the flow rate of the cleaning fluid flowing from the channel to the second chamber when no flow of the cleaning fluid is provided through the second cleaning fluid inlet.
22. The lithographic apparatus of claim 21, wherein the controller is configured to provide a flow of cleaning fluid through the second cleaning fluid inlet that is between 50% and 200% of the flow of cleaning fluid from the channel to the second chamber when no cleaning fluid flow is provided through the second cleaning fluid inlet.
23. A device manufacturing method using a lithographic apparatus, the method comprising:
projecting the patterned radiation beam onto a substrate using a projection system in the first chamber;
supporting the substrate using a substrate table in the second chamber;
providing a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of a cleaning fluid, a perimeter of the channel being defined by a wall; and, a step of, in the first embodiment,
cooling the walls of the channels;
wherein a cleaning fluid inlet for injecting a cleaning fluid is provided at the wall of the channel, and a portion of the wall of the channel located below the cleaning fluid inlet is cooled, and a portion of the wall of the channel located above the cleaning fluid inlet of the wall of the channel is heated.
24. The device manufacturing method of claim 23, further comprising cooling the cleaning fluid before the cleaning fluid reaches the channel.
25. The device manufacturing method according to claim 23 or 24, further comprising: the temperature of the wall of the channel is measured and cooling of the wall of the channel is controlled based on the measured temperature of the wall of the channel.
26. The device manufacturing method according to claim 23 or 24, further comprising heating a portion of the wall of the channel above a cleaning fluid inlet of the wall of the channel.
27. The device manufacturing method of claim 23 or 24, further comprising cooling the walls of the channels to a temperature between 8 ℃ and 15 ℃.
28. The device manufacturing method according to claim 23 or 24, further comprising: calibrating the cooling of the walls of the channel such that a relationship between the temperature of the walls of the channel and an overlay error of the lithographic exposure occurring during the cooling of the walls of the channel is determined, wherein the calibrating comprises a first step of cooling the walls to a desired temperature, a second step of performing the lithographic exposure on the substrate, and a third step of processing the substrate and measuring the overlay error of the lithographic exposure.
29. A device manufacturing method using a lithographic apparatus, the method comprising:
projecting the patterned radiation beam onto a substrate using a projection system in the first chamber;
supporting the substrate using a substrate table in the second chamber;
providing a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of a cleaning fluid, a perimeter of the channel being defined by a wall; and, a step of, in the first embodiment,
Providing different flows of cleaning fluid to the channel through different sections of the cleaning fluid inlet of the wall of the channel;
wherein a portion of the wall of the channel below the cleaning fluid inlet is cooled and a portion of the wall of the channel above the cleaning fluid inlet of the wall of the channel is heated.
30. The device manufacturing method of claim 29, wherein the flow rate of the cleaning fluid provided to the different sections of the cleaning fluid inlet is at least partially dependent on the ratio of the size of the cross-sectional area of the channel to the total length of the sections of the cleaning fluid inlet that provide cleaning fluid to the cross-sectional area of the channel.
31. A device manufacturing method using a lithographic apparatus, the method comprising: projecting a patterned beam of radiation onto a substrate supported by a substrate table in a second chamber using a projection system in a first chamber, the patterned beam of radiation reaching the second chamber from the first chamber via a channel, the periphery of the channel being defined by walls in which an angled cleaning fluid inlet having curved inner walls is provided, wherein the method further comprises providing cleaning fluid into the channel through the angled cleaning fluid inlet;
Wherein a portion of the wall of the channel below the cleaning fluid inlet is cooled and a portion of the wall of the channel above the cleaning fluid inlet of the wall of the channel is heated.
32. The device manufacturing method of claim 31, wherein the inner wall of the cleaning fluid inlet is curved such that cleaning fluid flows along a converging flow path.
33. A device manufacturing method using a lithographic apparatus, the method comprising: projecting the patterned radiation beam onto a substrate using a projection system in the first chamber; supporting the substrate using a substrate table in the second chamber; providing a channel extending between the first chamber and the second chamber, the channel being peripherally defined by a wall; providing a cleaning fluid to the walls of the channel from a first cleaning fluid inlet and a second cleaning fluid inlet, the second cleaning fluid inlet being positioned closer to the substrate than the first cleaning fluid inlet; and providing a cleaning fluid through the second cleaning fluid inlet, wherein the flow rate of providing cleaning fluid is based on the flow rate of cleaning fluid flowing from the channel to the second chamber when no cleaning fluid is provided through the second cleaning fluid inlet;
Wherein a portion of the wall of the channel below the cleaning fluid inlet is cooled and a portion of the wall of the channel above the cleaning fluid inlet of the wall of the channel is heated.
34. The device manufacturing method of claim 33, further comprising: providing a flow of cleaning fluid through the second cleaning fluid inlet is equal to the flow of cleaning fluid from the channel to the second chamber when no cleaning fluid is provided through the second cleaning fluid inlet.
35. A cooling system for a lithographic apparatus, the lithographic apparatus comprising:
a first chamber comprising a projection system configured to project a patterned radiation beam onto a substrate;
a second chamber comprising a substrate table configured to hold a substrate;
a channel extending between the first chamber and the second chamber, the channel configured to receive a flow of a cleaning fluid, a perimeter of the channel defined by a wall; and is also provided with
A cooling system configured to cool the wall of the channel;
wherein a cleaning fluid inlet for injecting a cleaning fluid is provided in the wall of the channel, and a portion of the wall of the channel located below the cleaning fluid inlet is cooled such that a fluid curtain formed by a cleaning fluid flow from the cleaning fluid inlet is cooled;
Wherein the lithographic apparatus further comprises a heating system configured to heat the PA193953
A portion of the wall of the channel above a cleaning fluid inlet of the wall of the channel.
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