Method relating to a lithographic apparatus

Abstract

The apparatus comprises a position monitoring system for determining the position of the substrate relative to a projection system that projects a radiation beam onto the substrate through an aperture, the position monitoring system having a component disposed below the projection system, and a baffle disposed between the aperture and the component.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to European Application No. 19166555.3, filed April 1, 2019, which is incorporated herein by reference in its entirety.

[0002] [Technical field] The present invention relates to a lithographic apparatus and related methods. [Background technology]

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate. Lithographic apparatus are used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus projects, for example, a pattern in a patterning device (e.g. mask) onto a layer of radiation-sensitive material (resist) formed on the substrate.

[0004] To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. Lithographic apparatus using extreme ultraviolet (EUV) radiation having a wavelength in the range of 4-20 nm, e.g. 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than lithographic apparatus using radiation having a wavelength of, e.g., 193 nm. Summary of the Invention [Problem to be solved by the invention]

[0005] Radiation incident on the resist can cause the release of components such as volatile organic compounds from the resist, also known as outgassing. The outgassing components can deposit on elements in the lithographic apparatus and cause contamination. Contamination of elements in the lithographic apparatus reduces the performance and lifetime of the apparatus.

[0006] It may be desirable to provide an improved lithographic apparatus in order to reduce the effects of contamination on performance or lifetime, or to overcome other disadvantages associated with lithographic apparatus. [Means for solving the problem]

[0007] In a first aspect of the present invention, there is provided a lithographic apparatus comprising a projection system which projects a radiation beam onto a substrate through an aperture in the projection system, a position monitoring system which determines a position of the substrate relative to the projection system, the position monitoring system having a component provided below the projection system, and a baffle located between the aperture and the component.

[0008] A lithographic apparatus may become contaminated, for example by outgassing from the resist on the substrate. Contamination of elements in the lithographic apparatus reduces the performance and / or lifetime of the apparatus. Contamination of elements, such as components of a position monitoring system, reduces the ability to determine the position of the substrate relative to the projection system. Providing a baffle in the lithographic apparatus can reduce or inhibit the transfer of contaminants from the substrate onto said components. The contaminants may be gaseous. Alternatively or additionally, the contaminants may be liquid or solid, which may be dispersed in a gas. The contaminants may move through the lithographic apparatus via a gas flow. The gas may carry contaminant particles from the substrate to said components. The baffle diverts or inhibits the flow of gas in the lithographic apparatus. The baffle diverts the flow of gas from a part of the substrate that is below the opening to at least a part of said component. Diverting or inhibiting the flow of gas reduces contaminant particles incident on said component. The baffle blocks a line of sight between the opening and a part of said component. The baffle may block a direct line of sight between at least a part of the component and an area of ​​the substrate directly beneath the opening. For example, the baffle may block a line of sight between an area of ​​the substrate directly beneath the opening and the first 5 cm of the component proximal to the opening. The substrate is placed on a substrate table, which may equate to the position of the substrate in normal use of the lithographic apparatus.

[0009] The lithographic apparatus may be an EUV lithographic apparatus. The aperture may be at a bottom end of the projection system. The bottom end is understood to be the end of the projection system facing the substrate. The aperture allows projection of a radiation beam from the projection system onto the substrate. The aperture may comprise a membrane that allows the radiation beam to pass while preventing gas flow. The position monitoring system may comprise, for example, an interferometer or a linear encoder. The position monitoring system is associated with the lithographic apparatus. A component of the position monitoring system is provided below the position monitoring system. The component may be closer to the aperture. The component may be closer to the substrate and / or a substrate table supporting the substrate.

[0010] The component may comprise a reflective surface, such as a reflective surface associated with an interferometry system. The position monitoring system may reflect a laser beam from the reflective surface. The component may comprise a scale, such as a scale associated with a linear encoder. The component may comprise a sensor. A baffle is provided to reduce contamination on a portion of the reflective surface, scale, etc.

[0011] The baffle has a baffle width. The baffle width is measured in a direction perpendicular to the direction from the substrate to the component and from the opening to the component. The baffle width may be the same as the scan direction. The baffle may have a cross-sectional shape extending along the baffle width. The component of the position monitoring system has a component width measured parallel to the baffle width. The baffle width is equal to or greater than the component width. Preferably, a baffle having a baffle width equal to or greater than the component width blocks all lines of sight between the opening and the component. Blocking a direct line of sight may more efficiently divert gas flow and reduce the likelihood of contaminants impinging on the component.

[0012] The lithographic apparatus may comprise a substrate table. The substrate table supports a substrate. In normal use of the lithographic apparatus, the substrate is placed on the substrate table. The baffle comprises a substantially vertical portion extending in a direction between the projection system and the substrate table. The vertical portion diverts gas flow from an exposure area to said component. Preferably, this reduces migration of contaminants from the exposure area to said component. The exposure area is the area of ​​the substrate below the aperture. The exposure area is defined as the area of ​​the substrate that receives radiation during operation of the lithographic apparatus. The vertical portion may block a direct line of sight between the exposure area and at least a part of said component. The vertical portion may, for example, block a line of sight between the exposure area and the first 5 cm from a side of said component close to the aperture.

[0013] The first portion of the baffle may extend along a first edge of the component. The first edge is the edge proximal to the opening. The second and third portions of the baffle may extend along a second and third edge of the component. The second and third edges are adjacent to the first edge. The second and third edges may be perpendicular to the first edge. The baffle extends around the open edge of the component. For example, the first, second and third portions may form a C-shaped baffle that extends around the edge of the component. Alternatively, the second and third portions may be joined by the first portion to form a V-shape. In this example, the second and third portions extend around the open edge of the component and the first, second and third portions extend along the first edge. By providing a baffle that extends around the edge of the component, more of the direct line of sight between the exposure area and the component can be blocked. In this way, the flow of gas between the exposure area and the component can be more effectively diverted. Thus, the contamination incident on said components can be reduced.

[0014] A portion of the baffle may comprise a getter, i.e., the baffle has a surface that preferentially captures molecules that come into contact with it. Trapping in this example may include absorption, adsorption, chemical bonding, or any other process that causes contaminants to adhere to the baffle. Getters include reactive materials such as aluminum, barium, magnesium, titanium, rare earth elements, etc. Getters may be formed by a surface coating on the baffle.

[0015] A portion of the baffle may be formed from a flexible material, the flexible material being flexible and bending upon contact with the second object. The portion may be, for example, a plastic material or rubber. Additionally or alternatively, a portion of the baffle may comprise a flexible structure, i.e. the flexible structure is flexible and bending upon contact with the second object. For example, the baffle may comprise a plurality of bristle members or a hollow structure. The baffle may comprise at least one plastic tube. A baffle provided with a flexible material and / or structure may minimize the impact of a baffle-substrate collision, i.e. if the baffle impacts the substrate, damage to the substrate and / or the baffle is minimized.

[0016] The projection system may further comprise a dynamic gas lock. The opening of the projection system corresponds to the opening in the dynamic gas lock. The opening may further comprise a membrane that blocks the flow of gas while allowing substantial transmission of radiation. The dynamic gas lock directs the gas towards the substrate table. The gas (whether static or dynamic) present between the substrate and the projection system forms a barrier against contaminants flying away from the substrate. If the gas is additionally moved towards the substrate, for example by flowing the gas in a direction towards the substrate through the dynamic gas lock, an additional protection is realised for contaminants not reaching the projection system. If the movement of gas from the dynamic gas lock is optimised, the flow of gas from the substrate to said components is reduced.

[0017] The baffle may be formed integrally with the projection system. The baffle may be formed integrally with the dynamic gas lock. In this example, the baffle forms a projection from the dynamic gas lock proximate the aperture in a direction towards the substrate.

[0018] The lithographic apparatus may further comprise a supply line delivering a gas towards the substrate and / or the substrate table. The supply line may be associated with the projection system and may in particular originate from a dynamic gas lock. The gas may be hydrogen. Alternatively, the gas may be an inert gas such as argon. The gas may be supplied to form a gas curtain between the substrate and said component. The gas may provide a purge to inhibit a flow of gas carrying contaminants from the substrate to said component.

[0019] A gas discharge end of the supply line may be located between the opening and said component. The gas discharge end may be associated with the projection system, in particular with a dynamic gas lock.

[0020] The gas discharge end of the supply line may be located between the baffle and said component. Optimizing the gas flow with respect to the baffle allows further diverting of the gas flow from the substrate to said component. In this way, an additional protection measure is realized for contaminants not to reach said component. By supplying gas near the face of the baffle facing the component, the gas pressure behind the baffle is increased. Behind is understood as between the baffle and said component. The increased gas pressure behind the baffle reduces the gas flow from the substrate to said component. Alternatively or additionally, the gas discharge end of the supply line may be located at the end of the baffle facing the substrate table. The gas supply line may be provided in an inner region of the baffle. The gas supply line and the gas discharge end provide a gas flow from the end of the baffle facing the substrate table to the substrate table.

[0021] The gas release tip has a gas release tip width. The gas release tip width is measured in a direction perpendicular to the direction from the substrate towards the component and from the opening towards the component. The gas release tip width is defined as the dimension of the gas release tip in the above direction. The gas release tip may be continuous along the gas release tip width or may be discontinuous along the gas release tip width, for example when the gas release tip comprises a plurality of holes formed across the gas release tip width. The gas release tip width may be the same as the scanning direction. The component has a component width measured parallel to the gas release tip width. The gas release tip width is equal to or greater than the component width. Preferably, a gas release tip having a width equal to or greater than the component width can reduce gas flow at all points between the opening and the component.

[0022] A first portion of the gas release edge extends along a first edge of the component. The first edge is an edge of the open side. A second portion and a third portion of the gas release edge extend along at least a portion of a second edge and a third edge of the component. The second edge and the third edge are adjacent to the first edge. The second edge and the third edge may be perpendicular to the first edge. The gas release edge extends around the open side edge of the component. For example, the first portion, the second portion, and the third portion may form a C-shaped gas release edge that extends around the edge of the component. Providing a gas release edge that extends around the edge of the component can reduce gas flow between an exposure region and the component. Providing a gas release edge that extends around the edge of the component can provide a contaminant-free purge gas flow to a larger portion of the component. In this way, contaminants incident on the component can be reduced.

[0023] In a second aspect of the invention, there is provided a method for reducing contamination in a lithographic apparatus. The method comprises projecting a beam of radiation through an aperture in a projection system onto an exposure area of ​​a substrate and determining a position of the substrate relative to the projection system by a position monitoring system, a component of the position monitoring system being provided below the projection system and a baffle being provided between the aperture and said component to divert gas flow between the exposure area and said component.

[0024] The lithographic apparatus may be an EUV lithographic apparatus. The aperture may be at a bottom end of the projection system. The bottom end is taken to be the end of the projection system facing the substrate. The aperture allows projection of a radiation beam from the projection system onto the substrate. The aperture may comprise a membrane that allows the radiation beam to pass while preventing gas flow. The aperture may be located at a bottom of the projection system. The bottom is taken to be the end of the projection system facing the substrate. The position monitoring system may comprise, for example, an interferometer or a linear encoder. The position monitoring system is associated with the lithographic apparatus. A component of the position monitoring system is provided below the position monitoring system. The component may be close to the aperture. The component may be close to the substrate and / or a substrate table supporting the substrate.

[0025] A lithographic apparatus may become contaminated, for example by outgassing from the resist on the substrate. Contamination of elements in the lithographic apparatus reduces the performance and / or lifetime of the apparatus. Contamination of elements, such as components of a position monitoring system, reduces the ability to determine the position of the substrate relative to the projection system. Providing a baffle in the lithographic apparatus can reduce or inhibit the transfer of contaminants from the substrate onto said components. The contaminants may be gaseous. Alternatively or additionally, the contaminants may be liquid or solid, which may be dispersed in a gas. The contaminants may move through the lithographic apparatus via a gas flow. The gas may carry contaminant particles from the substrate to said components. The baffle deflects or inhibits the flow of gas in the lithographic apparatus. The baffle deflects the flow of gas from a part of the substrate that is below the opening to at least a part of said components. By deflecting or inhibiting the flow of gas, fewer contaminant particles are incident on said components. The baffle blocks a direct line of sight between the opening and said components. The baffle may block a direct line of sight between the component and a region of the substrate directly beneath the opening. The baffle has a cross-sectional shape that extends in a direction perpendicular to a direction from the opening toward the substrate and to the component. The extending baffle eliminates a direct line of sight between all portions of the component and all portions of the opening.

[0026] The component may comprise a reflective surface, such as a reflective surface associated with an interferometry system. The position monitoring system may reflect a laser beam from the reflective surface. The component may comprise a scale, such as a scale associated with a linear encoder. The component may comprise a sensor. A baffle is provided to reduce contamination on a portion of the reflective surface, scale, etc.

[0027] The method further comprises providing a baffle that blocks a line of sight between an exposure area and at least a portion of the component. The baffle has a baffle width. The baffle width is measured in a direction perpendicular to the direction from the substrate to the component and from the opening to the component. The baffle width may be the same as the scan direction. The component has a component width measured parallel to the baffle width. The baffle width is equal to or greater than the component width. The baffle has a cross-sectional shape that extends in a direction perpendicular to the direction from the opening to the substrate and from the opening to the component. Preferably, the baffle, having a width equal to or greater than the component width, blocks all direct lines of sight between the opening and the component. Blocking direct lines of sight can more efficiently divert gas flow and reduce the likelihood of contaminants impinging on the component.

[0028] The method further comprises providing a baffle having a baffle height defined as the dimension of the baffle in a direction between the projection system and the substrate, the baffle height being set to block all line of sight between the exposure area and at least the first 5 cm from the side proximal to the opening in said component.

[0029] The method further includes trapping the contaminant particles with a getter formed on a portion of the baffle, i.e., the baffle has a surface that preferentially traps molecules that come into contact with it. Trapping in this example may include absorption, adsorption, chemical bonding, or any other process that causes the contaminants to adhere to the baffle. Getters include reactive materials such as aluminum, barium, magnesium, titanium, rare earth elements, etc. The getter may be formed by a surface coating on the baffle.

[0030] The method further comprises the step of supplying an additional gas flow from the projection system towards the substrate. The gas flow is supplied by a gas supply line. The supply line may be associated with the projection system and may in particular originate from a dynamic gas lock. The gas may be hydrogen. Alternatively, the gas may be an inert gas such as argon. The gas may be supplied to form a gas curtain between the substrate and said component. The gas may provide a purge to suppress a flow of gas carrying contaminants from the substrate to said component. The supply line may deliver the gas towards the baffle. By optimizing the flow of gas with respect to the baffle, the flow of gas from the substrate to said component may be further diverted. In this way, an additional protection is achieved for contaminants not reaching said component. A part of the gas discharge end of the supply line may be located between the opening and said component. A part of the gas discharge end may be located at the end of the baffle facing the substrate table. There may be one or more supply lines. The one or more supply lines are located in an inner region of the baffle.

[0031] The projection system may further comprise a dynamic gas lock. The opening of the projection system corresponds to the opening in the dynamic gas lock. The dynamic gas lock directs the gas to the substrate table. The gas (static or dynamic) present between the substrate and the projection system forms a barrier against contaminants flying away from the substrate. If the gas additionally moves towards the substrate, for example by flowing the gas in a direction towards the substrate through the dynamic gas lock, an additional protection is realized for contaminants not to reach the projection system. If the movement of gas from the dynamic gas lock is optimized, the flow of gas from the substrate to said components is reduced. The baffle may be formed by a part of the dynamic gas lock. In this example, the baffle constitutes a projection from the dynamic gas lock close to the opening in a direction towards the substrate. The gas discharge end may be associated with the projection system, in particular with the dynamic gas lock.

[0032] The method further comprises providing an increased gas pressure between the baffle and the component. By providing gas adjacent a face of the baffle facing the component, the gas pressure is increased behind the baffle, where behind is understood to be between the baffle and the component. The increased gas pressure behind the baffle reduces the flow of gas from the substrate to the component.

[0033] In a third aspect of the present invention there is provided a device manufactured using the apparatus or method described above. The device may be an integrated circuit. [Brief description of the drawings]

[0034] Hereinafter, an embodiment of the present invention will be described by way of example with reference to the schematic drawings. [Figure 1] 1 depicts a lithography system comprising a lithographic apparatus and a radiation source. [Diagram 2] 2 shows a part of a projection system with a baffle; [Diagram 3] 4 shows part of a projection system with a baffle in another exemplary arrangement; [Figure 4] 4 shows part of a projection system with a baffle in another exemplary arrangement; [Diagram 5] 2 shows a part of a projection system including a baffle and a gas supply line; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Figure 1 shows a lithography system comprising a radiation source SO and a lithographic apparatus LA. The source SO generates a beam of EUV radiation B and provides the beam of EUV radiation B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT for supporting a patterning device MA (e.g. a mask), a projection system PS, and a substrate table WT for supporting a substrate W. The substrate is also known as a wafer. The substrate table WT is also called a substrate support.

[0036] The radiation source SO shown in Fig. 1 is, for example, of the type also called a Laser Produced Plasma (LPP) source. The laser system 1 is, for example, a CO 2 The laser includes a laser, and a laser beam 2 is injected into a fuel, such as tin (Sn), supplied from a fuel emitter 3 or the like. In this embodiment, tin is exemplified, but any suitable fuel can be used. The fuel can be, for example, in liquid form, or a metal or alloy. The fuel emitter 3 can include a nozzle for directing, for example, small droplets of tin along a trajectory toward the plasma formation region 4. The laser beam 2 is incident on the tin in the plasma formation region 4. The injection of laser energy into the tin generates a tin plasma 7 in the plasma formation region 4. Radiation, including EUV radiation, is emitted from the plasma 7 during de-excitation and recombination of electrons with ions of the plasma. The radiation source SO can be a discharge produced plasma (DPP) source, a free electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0037] The illumination system IL conditions the EUV radiation beam B before it is incident on the patterning device MA. The illumination system IL may include a facetted field mirror device 10 and a facetted pupil mirror device 11. The combination of the facetted field mirror device 10 and the facetted pupil mirror device 11 provides an EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may include other mirrors or devices in addition to or instead of the facetted field mirror device 10 and the facetted pupil mirror device 11.

[0038] After the above conditioning, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. The projection system PS projects the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may comprise a number of mirrors 13, 14 that project the patterned EUV radiation beam B' onto the substrate W held by a substrate table WT. After the radiation beam B' leaves the projection system PS through an aperture 16 in the projection system PS, it is projected onto a portion E of the substrate W. The portion E of the substrate W that is irradiated with the patterned radiation beam B' generally corresponds to the area of ​​the substrate W directly under the aperture 16 and is also referred to as the exposure area E.

[0039] In normal operation, such as during exposure, the substrate W is supported on the substrate table WT. When in position, the substrate W is typically parallel to the substrate table WT. However, in some cases the substrate W may be absent. Thus, directional expressions relative to the substrate W (e.g. a direction towards the substrate W) may be interpreted as synonymous with directional expressions relative to the substrate table WT (e.g. a direction towards the substrate table WT).

[0040] To clarify the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes: an x-axis or x-direction, a y-axis or y-direction, and a z-axis or z-direction. Each of the three axes is orthogonal to the other two. In describing the apparatus, the x-axis and y-axis are taken in the plane of the substrate table WT and the z-axis is taken orthogonal to the substrate table WT, as shown in FIG. 1. The x-axis is further taken parallel to the direction from the aperture 16 to the mirror 18. The lithographic apparatus has a scan direction in which radiation is scanned over a portion of the substrate W. In the present embodiment, the scan direction is taken in the y-direction. The use of the coordinate system is for illustrative purposes and is not intended to limit the invention. The apparatus may be oriented in a different way without departing from the scope of the invention. For example, in the present embodiment, the direction from the aperture 16 to the mirror 18 is orthogonal to the scan direction, but the direction connecting the aperture 16 and the mirror 18 may be parallel to the scan direction or any other direction.

[0041] Directional terms are also used for the sake of clarity. The projection system PS may be construed as being "above" the substrate table WT. In this way, the patterned radiation beam B' travels from the projection system PS to an exposure area E of the substrate W which is "below" the projection system. The terms "above" and "below" may be construed as being relative to the z-axis as defined in Figure 1. The directional terms are not intended to limit the invention and the apparatus may be oriented differently than described without departing from the scope of the invention.

[0042] The projection system PS may apply a demagnification factor to the patterned EUV radiation beam B' to form images of features that are smaller than corresponding features on the patterning device MA, for example a demagnification factor of 4 or 8. Although in this embodiment the projection system PS has only two mirrors 13, 14 in Figure 1, the projection system PS may include any different number of mirrors (for example 6 or 8).

[0043] Substrate W may contain a pre-formed pattern, in which case lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B' to the pre-formed pattern on substrate W.

[0044] The substrate table WT may be capable of accurately positioning the substrate support WT, and therefore the substrate W, relative to the projection system PS. For example, the substrate support WT may be connected to a positioner, such as a linear motor positioner.

[0045] Two position monitoring systems PMS may be provided to monitor the positions of the substrate support WT and the substrate W relative to the projection system PS. In the illustrated example, the position monitoring system PMS is constituted by an interferometry system. However, in other embodiments, the position monitoring system PMS may be, for example, a linear encoder with a sensor, a scale. Many position monitoring systems PMS are known in the art. The components of the position monitoring system 18 are generally associated with an area below the projection system PS. The components 18 may be located below the projection system PS or may be, for example, fixed to the bottom of the projection system PS. The components 18 may be elements of the position monitoring system PMS, such as, for example, a mirror in an interferometry system or a scale in a linear encoder. The components may be sensors. One purpose of the parts 18 is to provide a reference surface with respect to the projection system PS and to aid in determining the position of the substrate table WT relative to the projection system. In the illustrated example, the invention is described for an interferometry system PMS with a mirror 18. However, this is not a limitation of the invention and the mirror 18 may be replaced by a different component of the position monitoring system PMS without departing from the scope of the invention.

[0046] In the illustrated example, each position monitoring system PMS comprises a reflective surface 18, hereinafter also referred to as mirror or positioning mirror 18. The mirror 18 is provided below the projection system PS. By reflecting light received from a coherent light source such as a laser beam L, the mirror 18 may be used to determine the displacement of the substrate table WT and substrate W relative to the projection system PS.

[0047] The mirror 18 may be associated with the projection system PS. The mirror 18 may be fixed to the projection system PS. The mirror 18 may also be associated with the substrate table WT. The mirror 18 may be fixed to the substrate table WT. The mirror 18 may be associated with the projection system PS or the substrate table WT via additional system elements. For example a frame may be provided to which the mirror 18 and the projection system PS and / or substrate table WT are mounted, for example by air mounts.

[0048] In the illustrated example, the mirror 18 is associated with the projection system PS. In operation, a laser beam L is generated by a laser LA. The laser beam L is directed to a beam splitter array. The beam splitter array comprises a beam splitter BS which splits the laser beam L into a first and a second part. The beam splitter array comprises at least one mirror 17 which directs the first part of the laser beam L to a detector DE. The second part of the laser beam L is directed to a 45 degree mirror M1 which is fixed to the substrate table WT at an angle of 45 degrees with respect to the xy plane. Although an angle of 45 degrees for the 45 degree mirror M1 is preferred for the illustrated apparatus, other geometries may be selected, for example mirrors at 30 degrees or other angles may be used. The 45 degree mirror M1 directs the second part of the laser beam L to the mirror 18. The mirror 18 reflects the second part towards the 45 degree mirror M1 which in turn directs the second part to a photodetector. The photodetector may determine the phase shift between the first and second portions of the laser beam L using interferometry to determine the displacement of the substrate table WT relative to the projection system PS.

[0049] In the illustrated example, two position monitoring systems PMS are shown, each with one positioning mirror 18. However, a different number of position monitoring systems may be provided. For example, one position monitoring system PMS or four position monitoring systems PMS may be provided. The illustrated example shows an arrangement suitable for determining the displacement of the substrate W in the z direction. Additional position monitoring systems and mirrors may be provided for determining the displacement of the substrate W in the x and y directions. There may be a relative vacuum within the projection system PS, with only a small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure. The area surrounding the substrate W is under ambient pressure. The area surrounding the substrate W may be broadly defined as the area between the substrate table WT and the edge of the projection system PS on the side of the substrate table WT. This area is also known as the chamber.

[0050] In a manufacturing process using a lithographic apparatus, a pattern is transferred onto a substrate W that is at least partially covered by a layer of radiation-sensitive material, also known as photoresist. The pattern is transferred by exposing the substrate W to a patterned radiation beam B', where the incident radiation chemically modifies the photoresist so that one or more portions of the photoresist defined by the pattern can be removed by a subsequent processing technique. Exposure of the photoresist may cause the release of components, such as volatile organic compounds, such as hydrocarbons. The release of components due to exposure of the photoresist is also known as outgassing. Components released due to outgassing are also referred to as outgassed components. Outgassed components may also be released without the exposure of the photoresist, i.e. outgassing may occur spontaneously.

[0051] The outgassing component may be, for example, a gas. The outgassing component may be a solid or a liquid, which may be dispersed in a gas. The outgassing component may flow through the lithographic apparatus via a gas flow path. The outgassing component is also known as a contaminant.

[0052] The outgassing components may deposit on other elements in the lithographic apparatus and cause contamination, in particular on the mirror 18 which is close to the area of ​​the substrate W below the aperture 16 (i.e. the exposure area of ​​the substrate W).

[0053] Contamination of the mirror 18 can significantly degrade the accuracy of the position monitoring system PMS. Accurate position monitoring is important to ensure optimal operation of the lithographic apparatus. For example, accurate position monitoring is crucial to improve exposure position accuracy and thus exposure and overlay resolution. An increasing amount of contamination on the mirror 18 can degrade the performance of the lithographic apparatus. As a result of the continuous build-up of contaminants on the mirror 18, the performance of the lithographic apparatus can deteriorate over time.

[0054] Contamination on the mirror 18 may also significantly reduce the lifespan of the position monitoring system PMS. As more contaminants accumulate on the mirror 18, the performance of the position monitoring system PMS and therefore the lithography apparatus may degrade and fall below the user's performance requirements. If the mirror 18 is covered with a large amount of contaminants, it may need to be replaced or cleaned. If the cleaning is performed manually, it requires invasive procedures on the lithography apparatus, which causes downtime in the lithography process. Downtime in the lithography process, which means lost production time, directly translates to a reduction in the output or productivity of the lithography process. Cleaning may also be automated, for example by chemical methods such as hydrogen radical generation or active heating. However, these automated cleaning methods are difficult to implement because the available space in the relevant part of the lithography apparatus is very limited. In addition, these automated cleaning methods may damage the substrate W or the lithography apparatus due to the heat input. The mirror 18 can be replaced, but this is not only expensive, but also causes downtime of the lithography process during the replacement procedure. It is therefore extremely important to reduce the chance of contamination of optical elements within the lithographic apparatus.

[0055] The present invention reduces contamination of the mirror 18 by providing a baffle 19 between the opening 16 and the mirror 18. The baffle 19 is provided to divert gas flow between the exposure area E of the substrate W (i.e. the area of ​​the substrate W below the opening 16) and the mirror 18. The baffle 19 may block a direct line of sight between the exposure area E and the mirror 18. As a result, many gas flow paths from the exposure area E to the mirror 18 are blocked by the baffle 19 and the gas flow is diverted. If the gas flow contains contaminants, diverting the gas flow can result in diverting the contaminants. In this way, the use of the baffle 19 can reduce the possibility of contamination of the mirror 18.

[0056] Although the flow of gases and / or contaminants from the substrate W to the mirror 18 is described herein, this may also be interpreted as a flow of gases and / or contaminants from the exposure area E of the substrate W. The contaminants are typically released in response to radiation B' passing through the aperture 16 and being incident on the exposure area E of the substrate W.

[0057] Optimizing the size, shape, and location of the baffle 19 and surrounding area can improve its effectiveness in reducing the likelihood of contamination of the mirror 18. Several example arrangements are described in detail below.

[0058] In some embodiments, a dynamic gas lock (DGL) is provided to reduce the flow of gas from the substrate W to the projection system PS. The DGL may direct gas to the substrate table. The flow of gas from the projection system PS towards the substrate table WT forms a barrier to contaminants entering the projection system from the substrate W. The DGL may include a membrane that blocks the flow of gas into the projection system PS whilst being substantially transparent to radiation. In this case, the flow of gas from the DGL prevents or reduces the deposition of contaminants on the membrane. However, the gas flow from the DGL may form an additional gas flow path, which may increase the possibility of contaminants migrating from the substrate W onto the mirror 18. Thus, in an apparatus using a DGL, a baffle 19 is particularly useful to divert the flow of gas from the substrate W to the mirror 18 and reduce the effects of contamination in the lithographic apparatus.

[0059] Several embodiments of lithographic apparatus comprising a baffle 19 between the aperture 16 and the mirror 18 will now be described with reference to Figures 2 to 5.

[0060] Figures 2A and 2B show part of a projection system PS and a substrate table WT according to an embodiment of the invention. The projection system PS comprises an aperture 16 through which radiation exits the projection system PS. Although the aperture 16 is shown diagrammatically as a rectangle, this is by way of example and is not limiting of the invention, as apertures of other shapes may be used. For example, the aperture may comprise a curved portion. The projection system PS further comprises two mirrors 18 associated with two position monitoring systems. Other components of the position monitoring systems have been omitted from the illustration for simplicity.

[0061] The substrate W is mounted on a substrate table WT below the projection system PS. The substrate W has an exposure area E defined as the area of ​​the substrate W below the aperture 16, i.e. the exposure area E is the area of ​​the substrate W that receives radiation during a running lithographic process. Outgassing components 21 are shown as being emitted from the surface of the substrate W following, for example, exposure of a resist on the substrate W.

[0062] The arrows indicate the gas flow paths in the lithographic apparatus. If no baffle 19 is provided, the gas flow would be isotropic around the exposure area E. As a result, contamination elements carried in the gas would move in all directions, in particular towards the mirror 18. As the gas flow in the x-direction is unimpeded, the movement of outgassing components 21 from the substrate W towards the mirror 18 may be promoted. Indeed, unless the gas flow paths are diverted, contamination would be deposited in all directions around the aperture 16. For example, contamination would be deposited in a ring around the aperture 16, covering parts of the mirror 18 as well.

[0063] In this embodiment, a baffle 19 is disposed between the opening 16 and each mirror 18 (i.e., two baffles 19 are provided). The baffles 19 are arranged to divert or restrict the flow of gas within the lithographic apparatus. In particular, the baffles 19 are arranged to divert the flow of gas from the exposure area E towards the mirror 18. As shown, the gas flow in the x-direction is impeded by the baffles 19. In this way, the chances of contaminants carried by the gas reaching and depositing on the mirror 18 are reduced. Thus, the baffles 19 reduce the chances of contaminant particles 21 landing on the mirror 18.

[0064] The baffle 19 is optimized such that a portion of the baffle functions as a getter. Getters are known in the art and preferentially capture molecules that come into contact with them. Getters are used, particularly in low pressure environments, to capture undesirable compounds (i.e., contaminants). Trapping in this example may include absorption, adsorption, chemical bonding, or any other process that attaches the contaminants to the getter. A getter may be used in conjunction with the baffle 19 to further reduce the likelihood of contaminants reaching the mirror 18. Many getters are known in the art, for example getters include reactive materials such as aluminum, barium, magnesium, titanium, rare earth elements, etc. The getter may be a portion of the baffle 19 or the entire baffle 19 may be a getter. The getter may be a surface coating on the baffle 19.

[0065] In this embodiment there are two baffles 19, but in other embodiments a different number of baffles may be provided. For example, in a lithographic apparatus with one position monitoring system PMS having one mirror 18, only one baffle 19 is needed. Preferably there are as many baffles 19 as there are mirrors 18.

[0066] The baffle 19 has a baffle height H, which is defined as the distance from the end of the baffle 19 at the substrate table WT to the end of the baffle 19 at the projection system PS. If the baffle 19 is attached directly to the projection system PS, then the baffle height H is equal to the distance from the end of the baffle 19 at the substrate table WT to the projection system PS. In the example shown, the baffle height H is the dimension of the baffle 19 in the z direction.

[0067] Baffle 19 has a baffle width Wb defined as the dimension of baffle 19 in the y-direction. Baffle 19 has a baffle thickness T defined as the dimension of baffle 19 in the x-direction.

[0068] The baffle 19 may block a direct line of sight between the exposure area E and the mirror 18. The baffle 19 may extend along the edge of the mirror 18 on the opening 16 side. The mirror 18 has a mirror width Wm. Preferably, the baffle 19 has a baffle width Wb that is equal to or greater than the mirror width Wm. The baffle 19 may extend beyond the edge of the mirror 18. A baffle width Wb that is greater than the mirror width Wm allows the baffle 19 to block more of the line of sight between the exposure area E and the mirror 18.

[0069] Gas diverted by the baffle 19 flows around the edge of the baffle 19. A baffle width Wb that is greater than the mirror width Wm may reduce the gas flow rate around the baffle 19. A baffle width Wb that is greater than the mirror width Wm may prevent the gas flowing around the edge of the baffle 19 from splashing onto the mirror 18.

[0070] The baffle 19 is disposed between the projection system PS and a substrate table WT which supports the substrate W. A space in which the baffle 19 resides is thus defined, which may alternatively be referred to as a chamber. The chamber has a chamber height C' which is defined as the distance in the z direction between the substrate table WT and the edge of the projection system PS facing the substrate table WT.

[0071] Due to motions and tolerances related to the lithographic process, the chamber height C' may vary during operation. For example, the chamber height C' changes when the substrate table WT is driven in the z-direction to change the focus of radiation during a lithographic exposure. Thus, during normal use of the lithographic apparatus, the chamber height C' may have a range of values. When considering the chamber height C' and the clearance C, it should be noted that during normal operation, the substrate W is supported on the substrate table WT. As a result, the distance between the substrate W and the baffle 19 is smaller than the chamber height C'. The clearance C is large enough such that the baffle 19 does not contact the substrate W during normal operation of the lithographic apparatus with the substrate W present. Normal operation includes planned events such as lithographic exposures and scans. Normal operation may also include uncontrollable events such as an earthquake.

[0072] An earthquake may occur during use of the lithographic apparatus. This may cause the substrate table W to move further towards the projection system PS than during normal use of the lithographic apparatus. Thus, there is a risk that the movement of the substrate table WT may cause the baffle 19 to collide with the substrate W. The same may occur during a malfunction of the lithographic apparatus. An impact between the baffle 19 and the substrate W may damage the baffle 19 and / or the substrate W. Damage to the substrate may lead to a reduced quality output and / or a time penalty such as a rerun of the lithographic process. If the substrate W is broken, fragments of the substrate W may be released into the lithographic apparatus as additional contamination, which may require cleaning. The clearance C is set to reduce the probability of such a collision. However, it cannot completely eliminate the possibility of a collision.

[0073] To increase the effectiveness of the baffle 19 in diverting the gas flow, it is preferable to provide the baffle 19 with a larger baffle height H. With a larger baffle height H, more of the direct line of sight between the exposure area E and the mirror 18 is blocked. If the baffle height H is too small, the gas can escape unimpeded from the exposure area E to the mirror 18. The baffle 19 blocks some of the direct line of sight between the exposure area E and the mirror 18. Preferably, the baffle 19 is provided with a baffle height H large enough to block all lines of sight between the exposure area and portions of the mirror.

[0074] On the other hand, a large baffle height H means a small clearance C. If the clearance C is too small, the risk of collision increases. The clearance C is, for example, larger than 3 mm. A clearance C larger than 3 mm is preferred to reduce the risk of collision between a typical substrate and the baffle 19. The clearance C larger than 3 mm is calculated using a typical substrate thickness. A typical substrate has a thickness of about 775 microns. The thickness of the substrate W may vary across the substrate surface, for example due to a non-uniform thickness. The clearance C is set taking into account the thickness of the substrate W. A larger clearance C is preferred for thicker substrates W. In other cases, such as locations with a low earthquake risk, a clearance C smaller than 3 mm may be sufficient.

[0075] Different baffle heights H and baffle clearances C are preferred for different lithography apparatuses having different chamber heights H', different focus conditions, etc. Thus, the baffle height H and clearance C are selected by the user. The baffle height H may be considered in relation to the cavity height C'. For example, the baffle ratio of the baffle height H to the cavity height C' is calculated as H / C'. A baffle ratio of more than 20% is preferred for diverting gas flow from the exposure region E to the mirror 18.

[0076] The baffle height H may be considered in terms of its ability to block the line of sight, i.e., to deflect gas flow along the line of sight. For example, the baffle height H is set to block all direct lines of sight between the exposure area E and a portion of the mirror 18. This portion is an area of ​​the mirror 18 that would receive a large amount of contaminants in the absence of the baffle 19. The size of this area varies depending on the lithographic apparatus and / or process. The baffle height H in the illustrated embodiment is set to block the line of sight between the exposure area E and the first 5 cm from the side of the mirror 18 near the opening. Other lithographic processes may block the line of sight to a larger area (e.g., 10 cm) or a smaller area (e.g., 2 cm) of the part.

[0077] To reduce the effect of the collision, the baffle 19 or parts of the baffle 19 are made of a flexible material. The flexible material is flexible and bends when it comes into contact with a second object. Thus, even if the baffle 19 hits the substrate W, damage to the substrate W and / or the baffle 19 is minimized. The flexible material is, for example, a plastic material or rubber. Additionally or alternatively, the part of the baffle 19 may comprise a flexible structure, such as a hollow structure such as a plurality of thin bristle members or one or more plastic tubes. If a plastic tube is used, the tube is arranged in a vertical direction, i.e. extending from the projection system PS towards the substrate W. A flexible structure may be understood as a structure designed to exhibit flexibility such that it bends when it comes into contact with a second object. Even if a flexible material and / or structure is provided, the baffle 19 is still sufficiently stiff to deflect the gas flow. That is, the baffle 19 bends when it comes into contact with the substrate W, but does not deform significantly when hit by the gas flow in the lithographic apparatus.

[0078] In the example shown in Figures 2A and 2B, the baffle 19 is a rectangular parallelepiped. This shape creates a barrier that deflects the gas flow. However, the shape of the baffle 19 can be optimized to control the gas flow in the chamber. For example, the baffle can have curved edges to reduce turbulence. Some other examples of baffle shapes are described below with reference to Figures 3 and 4.

[0079] 3A and 3B show a baffle 19 having a horizontal portion 19a and a vertical portion 19b. The baffle extends a significant length in the x-direction before extending downward in the z-direction. In this example, the baffle shape is generally L-shaped, where a bend 19c interconnects the horizontal and vertical portions 19a, 19b. This shape is preferred for manufacturing purposes.

[0080] In this example, the projection system PS further comprises a dynamic gas lock (DGL) 20. As previously mentioned, the DGL 20 directs gas towards the substrate table WT (as indicated by the gas flow arrows in Figure 3A). The DGL 20 is supplied with gas through supply lines leading from other parts of the projection system PS or from an external source (not shown). The DGL 20 is formed to reduce the likelihood of gas migrating upwards towards the projection system PS and to form a barrier to contaminants 21 migrating from the substrate W to the projection system PS. Apparatus utilizing the DGL 20 particularly benefits from the use of a baffle 19, as an additional gas flow path is provided and the baffle 19 deflects contaminant carrying gas flows, reducing the effect of contamination of the lithographic apparatus. When the baffle 19 is used in combination with the DGL 20, the baffle 19 or parts 19a, 19b, 19c of the baffle 19 may be formed integrally with the DGL 20.

[0081] Another baffle shape is shown in Figures 4A and 4B. In this embodiment, the baffle 19 is curved when viewed from below. The baffle 19 extends along the proximal edge 18a of the mirror 18 (the edge of the mirror 18 closest to the opening 16). Because the baffle 19 is curved, it also extends partially along the adjacent side edges 18b, 18c of the mirror 18. Preferably, this shape partially surrounds the edge of the mirror 18 that faces the opening 16. By partially surrounding the edge of the mirror 18, more of the direct line of sight between the substrate W and the mirror 18 can be blocked, further reducing the chance of contaminants impinging on the mirror 18. Although a C-shaped baffle 19 is illustrated here, other shapes of the baffle 19 that extend around the side edges 18b, 18c of the mirror 18 adjacent the proximal end of the mirror can achieve similar results.

[0082] The baffle 19 may also be "V-shaped" when viewed from below. That is, a baffle 19 may have first and second straight sections connected to each other at one end, where the first and second sections are connected at an angle to form a chevron or V-shape. The angle may be varied to form a narrower or wider V-shape. The V-shaped baffle 19 is suitable for diverting gas flow away from the mirror 18. The V-shaped baffle 19 may extend around adjacent side edges 18b, 18c of the mirror 18 and partially surround the end of the mirror 18 facing the aperture 16.

[0083] The projection system PS in Figures 4A and 4B also comprises a DGL 20. In some examples, the use of the DGL 20 in combination with a baffle 19 can provide advantageous effects. In particular, the gas flow from the DGL 20 can be further optimized relative to the baffle 19 to more effectively divert the gas flow from the substrate W to the mirror 18. In addition, new gas supply paths can be easily created as gas supply lines are already provided within the DGL member. Some implementations for optimizing the gas flow are described below with reference to Figures 5A-C.

[0084] The projection system PS in Figures 5A-C comprises two baffles 19 and two gas supply lines 22. The gas supply lines 22 are provided to deliver gas towards the substrate W and / or substrate table WT. This gas forms a gas curtain between the substrate W and the mirror 18, reducing the flow of contaminant-carrying gas from the substrate W to the mirror 18. This is also called local purge, purge flow or purge gas flow. The local purge has the effect of diverting the gas flow from the substrate W to the mirror 18. The local purge creates conditions in which clean (i.e. contaminant-free) gas flows over the mirror 18, further reducing the chance of contaminants getting onto the mirror 18. The purge gas replaces the contaminant-carrying gas in the vicinity of the mirror 18.

[0085] In the illustrated example, the gas is supplied by a gas supply line 22 associated with the DGL 20. Alternatively, the gas supply line 22 may be associated with the projection system PS. For example, the gas is supplied through a delivery tube attached to the underside of the projection system PS. When gas supply lines 22 are used, there are as many supply lines 22 as there are baffles 19 and / or mirrors 18. For example, when only one baffle 19 is used, there may be only one supply line 22. Alternatively, one supply line may be used to supply a gas flow around multiple baffles. Alternatively, there may be multiple supply lines 22. When there are multiple supply lines 22, multiple supply lines may be associated with one baffle 19, or multiple supply lines may be associated with multiple baffles. The gas is, for example, hydrogen. Hydrogen is already used in some known lithography processes, so the barrier to use is low. The gas may be a non-reactive gas, such as an inert gas, for example argon. Argon is a heavier molecule than hydrogen, so it may more effectively suppress outgassing components. On the other hand, argon is less available and / or more expensive than hydrogen.

[0086] The supply line 22 has a gas discharge end 24. Gas in the supply line 22 enters the chamber below the projection system PS from the gas discharge end 24. The gas discharge end 24 of the supply line 22 is arranged such that a gas flow is provided between the end of the baffle 19 on the substrate table WT or substrate W side. For example, the gas supply line 22 is arranged inside the baffle 19. The gas discharge end 24 of the supply line is located at the end of the baffle 19 on the substrate table WT side. In this way, gas is injected into the baffle 19 via the gas supply line 22, causing gas to flow from the end of the baffle 19 downwards towards the substrate table WT. The gas flow at the end of the baffle 19 reduces the flow of gas from the exposure area E to the mirror 18.

[0087] Alternatively or additionally, the gas discharge end 24 of the supply line 22 may be located between the opening 16 and the mirror 18. In particular, the supply line 22 is arranged to deliver gas adjacent to the face 19a of the baffle 19 facing the mirror 18. This is achieved by locating the gas discharge end 24 of the supply line between the baffle 19 and the mirror 18. The gas discharge end 24 and the supply line 22 may be arranged to direct the gas adjacent to the face 19a of the baffle 19 facing the mirror 18. In this example, the gas is still directed in a downward direction, i.e. from the projection system PS towards the substrate W, but flows downward along the face 19a of the baffle 19. By supplying gas adjacent to the face 19a, the gas pressure in the region between the baffle 19 and the mirror 18 is increased. The pressure difference caused by the increased gas pressure in this region reduces the flow of gas from the exposure area E to the mirror 18.

[0088] The gas supply line 22 may be used together with the baffle 19. This provides an effective method for reducing the possibility of contaminants impinging on the mirror 18. That is, the baffle 19 diverts the gas flow between the exposure area E and the mirror 18, and the gas supply line 22 provides a purge gas flow of contaminant-free gas and further reduces the gas flow between the exposure area E and the mirror. In another example, the gas supply line 22 may be used without the baffle 19. For example, if no baffle is provided, the gas discharge end 24 of the gas supply line 22 may be disposed between the opening 16 and the mirror 18. By disposing the gas discharge end 24 of the supply line 22 between the opening 16 and the mirror 18, a gas curtain is formed that reduces the flow of gas from the exposure area E to the mirror 18. In addition, by providing a gas purge flow, a contaminant-free gas flow is provided on the mirror 18, so that the possibility of contaminants impinging on the mirror 18 can be sufficiently reduced even without the use of the baffle 19. However, it is preferred to use the gas supply line 22 together with the baffle 19 in order to more effectively reduce contamination of the lithographic apparatus.

[0089] The location of the gas discharge end 24 of the supply line 22 is selected to provide good control of the flow of purge gas. Two examples of the gas discharge end 24 are shown in Figures 5B and 5C. The shape of the baffle 19 in these examples is similar to that of Figure 2, although baffles 19 of other shapes and sizes may be used with the gas supply line 22.

[0090] In the arrangement shown in FIG. 5B, the cross-sectional shape of the gas discharge end 24 is elongated. The elongated gas discharge end 24 may be called a slot. The extension direction here is the y direction. The extension width Wg of the gas discharge end 24 is equal to or greater than the mirror width Wm. This allows a gas curtain to be formed along the entire length of the mirror 18 in the y direction. In addition, a purge flow that does not contain contaminants is supplied to a larger area of ​​the mirror 18, further reducing the risk of contaminants adhering to the mirror 18. The extension width Wg of the gas discharge end 24 is equal to or greater than the baffle width Wb. This allows the gas flow to be reduced at all points between the baffle 19 and the mirror 18.

[0091] FIG. 5C shows another arrangement that differs from the elongated gas discharge tip. This example utilizes a gas discharge tip 24 with a plurality of holes. The holes 24 in this example are arranged in a line to form a row of holes 24 extending in the y direction. Such a row of holes is easier to manufacture than an elongated slot. As in the example of FIG. 5B, the width of the row of holes 24 preferably extends to at least the mirror width Wm. This provides a gas curtain along the entire length of the mirror 18 in the y direction. This also provides more areas of the mirror 18 with contaminant-free purge flow, further reducing the risk of contaminants depositing on the mirror 18. The width of the row of holes 24 extends to at least the baffle width Wb. This reduces the gas flow at all points between the baffle 19 and the mirror 18. Although four holes are shown in the illustrated example, any number of holes is possible. In this example, the row of holes 24 extends along a first side of the mirror 18.

[0092] In the arrangement shown in Figures 5B and 5C, the gas discharge end 24 extends along the edge 18a of the mirror 18 on the opening 16 side. The gas discharge end 24 preferably extends further along a portion of the adjacent side edges 18b, 18c of the mirror 18. For example, the gas discharge end 24 is curved and extends around the edge of the mirror 18 on the opening 16 side, similar to the baffle 19 shown in Figures 3A and 3B. The gas discharge end 24 extending around the edge of the mirror 18 forms an effective barrier to protect the larger portion of the mirror 18 from contaminants flying off the substrate W. The gas discharge end 24 extending around the edge of the mirror 18 forms a contaminant-free purge gas flow towards the larger portion of the mirror 18.

[0093] The term "projection system" (PS) should be interpreted broadly to encompass various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination of these, appropriate for the exposure radiation used.

[0094] Although specific reference has been made to the use of lithographic apparatus in the manufacture of integrated circuits, the lithographic apparatus may be used in other applications, for example, in 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.

[0095] Although specific reference has been made to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may form part of other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, metrology apparatus, or other apparatus that measures or processes objects, such as wafers (or other substrates) or masks (or other patterning devices). These apparatus are commonly collectively referred to as lithography tools.

[0096] Although the specific embodiment of the present invention has been described above, the present invention may be implemented in a manner other than the embodiment. The above description is illustrative and is not intended to limit the present invention. Therefore, it is obvious to those skilled in the art that modifications can be made to the present invention without departing from the spirit of the present invention.

[0097] Item 1: a projection system configured to project a beam of radiation onto a substrate through an aperture in the projection system; a position monitoring system for determining the position of the substrate relative to the projection system, the position monitoring system components being provided below the projection system; and a baffle disposed between the opening and the component; 1. A lithographic apparatus comprising:

[0098] Item 2: Item 2. A lithographic apparatus according to item 1, wherein the component comprises a reflective surface of an interferometer or a scale of a linear encoder.

[0099] Item 3: The baffle has a baffle width; the component has a component width measured parallel to the baffle width; The baffle width is equal to or greater than the component width; Item 3. A lithographic apparatus according to item 1 or 2.

[0100] Item 4: a substrate table for supporting a substrate; the baffle having a substantially vertical portion extending in a direction between the projection system and the substrate table; 4. A lithographic apparatus according to any of items 1 to 3.

[0101] Item 5: a first portion of the baffle extending along a first edge of an open side of the component; the second and third portions of the baffle extend along at least a portion of the second and third edges of the component; the second edge and the third edge are adjacent to the first edge; 5. A lithographic apparatus according to any of items 1 to 4.

[0102] Item 6: 6. A lithographic apparatus according to any of items 1 to 5, wherein a part of the baffle constitutes a getter.

[0103] Item 7: 7. A lithographic apparatus according to any of items 1 to 6, wherein part of the baffle is formed by a flexible material.

[0104] Item 8:

[0023] The projection system further comprises a dynamic gas lock; an aperture in the projection system corresponds to an aperture in the dynamic gas lock; 8. A lithographic apparatus according to any of items 1 to 7.

[0105] Item 9: 9. A lithographic apparatus according to any of items 1 to 8, wherein the baffle is integrally formed with the projection system.

[0106] Item 10: 10. A lithographic apparatus according to any of the preceding items, further comprising a supply line for delivering a gas towards the substrate.

[0107] Item 11: projecting a beam of radiation through an aperture in a projection system onto an exposure area of ​​a substrate; determining a position of the substrate relative to the projection system by a position monitoring system; Equipped with a position monitoring system component is disposed below the projection system; a baffle is provided between the opening and the component to divert gas flow between the exposure area and the component; A method for reducing contamination of a lithographic apparatus.

[0108] Item 12: Item 12. The method of item 11, wherein the component comprises a reflective surface of an interferometer or a scale of a linear encoder.

[0109] Item 13: 13. The method of claim 11 or 12, wherein the baffle is positioned to block a line of sight between the exposure area and at least a portion of the component.

[0110] Item 14: the baffle has a baffle height defined as the dimension of the baffle in a direction between the projection system and the substrate; the baffle height is set to block all line of sight between the exposure area and at least the first 5 cm from the side proximal to the opening in the component; 14. The method according to any one of items 11 to 13.

[0111] Item 15: 15. The method according to any of items 11 to 14, further comprising a step of trapping contaminant particles with a getter.

[0112] Item 16: 16. The method according to any of items 11 to 15, further comprising the step of providing an additional gas flow from the projection system towards the substrate.

[0113] Item 17: Item 17. The method of item 16, further comprising the step of providing an elevated gas pressure between the baffle and the portion of the position monitoring system.

[0114] Item 18: 18. A device manufactured using the apparatus according to any one of items 1 to 10 or the method according to any one of items 11 to 17.

Claims

1. a position monitoring system for determining a position of the substrate relative to a projection system which projects a radiation beam through an aperture onto the substrate for control by a positioner, the position monitoring system having components fixed to a bottom of the projection system; a baffle disposed between the opening and the component; a supply line for delivering gas to the substrate; Equipped with The gas discharge end of the supply line is disposed between the baffle and said component of the position monitoring system.

2. The apparatus of claim 1 , wherein the component comprises a reflective surface of an interferometer or a scale of a linear encoder.

3. The baffle has a baffle width; the component has a component width measured parallel to the baffle width; The baffle width is equal to or greater than the component width; 3. Apparatus according to claim 1 or 2.

4. a substrate table for supporting a substrate; the baffle having a substantially vertical portion extending in a direction between the projection system and the substrate table; 4. Apparatus according to any one of claims 1 to 3.

5. a first portion of the baffle extending along a first edge of an open side of the component; the second and third portions of the baffle extend along at least a portion of the second and third edges of the component; The second edge and the third edge are adjacent to the first edge.

5. Apparatus according to any one of claims 1 to 4.

6. A portion of the baffle is formed of a getter and / or a flexible material; [0023] The projection system further comprises a dynamic gas lock; an aperture in the projection system corresponds to an aperture in the dynamic gas lock; 6. Apparatus according to any one of claims 1 to 5.

7. An apparatus according to any preceding claim, wherein the baffle is integrally formed with the projection system.

8. the gas discharge end has a gas discharge end width; the component of the position monitoring system has a component width measured parallel to a gas discharge end width; The gas discharge end width is equal to or greater than the component width; 8. Apparatus according to any one of claims 1 to 7.

9. a first portion of the gas discharge end extends along a first edge of the open side of the component; the second and third portions of the gas discharge end extend along at least a portion of the second and third edges of the component; The second edge and the third edge are adjacent to the first edge.

9. Apparatus according to any one of claims 1 to 8.

10. A lithographic apparatus comprising an apparatus according to any one of claims 1 to 9.

11. projecting a beam of radiation through an aperture in a projection system onto an exposure area of ​​a substrate; determining by a position monitoring system a position of the substrate relative to the projection system for control by a positioner; Equipped with A component of the position monitoring system is fixed to the bottom of the projection system; a baffle is provided between the opening and the component to divert gas flow between the exposure area and the component; A supply line is provided to deliver gas to the substrate, a gas discharge end of the supply line disposed between the baffle and said component of the position monitoring system; A method for reducing equipment contamination.

12. A method for manufacturing a device using an apparatus according to any one of claims 1 to 10 or a method according to claim 11.

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