Lithographic apparatus and related methods

Abstract

An apparatus comprising: a position monitoring system configured to determine a position of a substrate relative to a projection system, the projection system configured to project a radiation beam through an opening in the projection system and onto the substrate, wherein a component of the position monitoring system is located below the projection system when in use; and a baffle disposed between the opening and the component.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to European application 19166555.3 filed on April 1, 2019, and the entire contents of said European application are incorporated herein by reference. Technical Field

[0003] The present invention relates to lithographic apparatus and related methods. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. For example, a lithographic apparatus may be used in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern at a pattern forming device (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0005] To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of a feature that can be formed on the substrate. A lithographic apparatus using extreme ultraviolet (EUV) radiation (having a wavelength in the range of 4 nm to 20 nm, such as 6.7 nm or 13.5 nm) may be used to form smaller features on a substrate than a lithographic apparatus using, for example, radiation having a wavelength of 193 nm.

[0006] Incident radiation on the resist may cause components (such as volatile organic compounds) to be released from the resist, which is also known as outgassing. Outgassing components may adhere to and thus contaminate components in the lithographic apparatus. Contamination of components in the lithographic apparatus may reduce the performance and service life of the apparatus.

[0007] It may be desirable to provide improved lithographic apparatus that reduces the effects of contamination on performance and lifetime, or overcomes some other disadvantage associated with lithographic apparatus. Summary of the invention

[0008] According to a first aspect of the present invention, a lithography device is provided, comprising: a projection system, which is configured to project a radiation beam through an opening in the projection system and onto a substrate; a position monitoring system, which is configured to determine the position of the substrate relative to the projection system, wherein a component of the position monitoring system is located below the projection system; and a baffle, which is arranged between the opening and the component.

[0009] The lithographic apparatus may be subject to contaminants, for example, due to degassing of resist from the substrate. Contaminants on components in the lithographic apparatus may reduce the performance and / or service life of the apparatus. Contaminants on components (such as components of the position monitoring system) may reduce the effectiveness of determining the position of the substrate relative to the projection system. Providing a baffle in the lithographic apparatus can reduce or limit the migration of contaminants from the substrate to the components. The contaminants may be gaseous. Alternatively or additionally, the contaminants may be liquid or solid and may be suspended in a gas. The contaminants may be transferred through the lithographic apparatus via an airflow. The gas may transfer contaminant particles from the substrate to the components. The baffle may deflect or limit the airflow within the lithographic apparatus. The baffle may deflect the airflow from a portion of the substrate located below the opening to at least a portion of the component. The deflection or restriction of the airflow may reduce the incidence of contaminant particles on the component. The baffle may block the line of sight between the opening and a portion of the component. The baffle may block a direct line of sight or direct sight between at least a portion of the component and an area of ​​the substrate directly below the opening. For example, the baffle may block a line of sight between an area of ​​the substrate directly below the opening and the first 5 cm of the component closest to the opening. The substrate may be located on a substrate table, which may be considered to be the position of the substrate during normal use of the lithographic apparatus.

[0010] The lithographic apparatus may be an EUV lithographic apparatus. The opening may be located at the lowermost end of the projection system. The lowermost end may be interpreted as the end of the projection system closest to the substrate. The opening may be configured to allow a radiation beam to be projected from the projection system onto the substrate. The opening may include a membrane configured to prevent airflow from passing through the opening while allowing the radiation beam to pass through the opening. The position monitoring system may include, for example, an interferometer or a linear encoder. The position monitoring system may typically be associated with the lithographic apparatus. A component of the position monitoring system may be disposed below the position monitoring system. The component may be closest to the opening. The component may be closest to the substrate and / or a substrate table configured to support a substrate.

[0011] The component may include a reflective surface, such as a reflective surface associated with an interferometric measurement system. The position monitoring system may reflect a laser beam off the reflective surface. The component may include a scale, such as a scale associated with a linear encoder. The component may include a sensor. The baffle may be provided to reduce contamination on a portion of the reflective surface, scale, or other component.

[0012] The baffle may have a baffle width. The baffle width may be measured perpendicular to a direction from the substrate to the component and a direction from the opening to the component. The baffle width may be defined along a scanning direction. The baffle may have a cross-sectional shape that is elongated along the baffle width. The component of the position monitoring system may have a component width measured parallel to the baffle width. The baffle width may be equal to or greater than the component width. Advantageously, a baffle having a width equal to or greater than the component width may block all lines of sight between the opening and the component. Blocking direct or direct lines of sight may deflect airflow more efficiently and thereby reduce the likelihood of contaminants impacting the component.

[0013] The lithographic apparatus may include a substrate stage. The substrate stage may be configured to support the substrate. When the lithographic apparatus is in normal use, the substrate may be arranged on the substrate stage. The baffle may include a substantially vertical portion extending in a direction substantially between the projection system and the substrate stage. The substantially vertical portion may deflect the airflow from the exposure area to the component. Advantageously, this may reduce the movement of contaminants from the exposure area to the component. The exposure area may be an area of ​​the substrate located below the opening. The exposure area may be defined as an area of ​​the substrate configured to receive radiation when the lithographic apparatus is in operation. The substantially vertical portion may block a direct line of sight or a direct view between the exposure area and at least a portion of the component. The substantially vertical portion may block, for example, a line of sight between the exposure area and the first 5 cm of the component closest to the opening.

[0014] The first portion of the baffle may extend along a first edge of the component. The first edge may be closest 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 may be adjacent to the first edge. The second and third edges may be perpendicular to the first edge. The baffle may extend approximately around the end of the component closest to the opening. For example, the first, second, and third portions may form a C-shaped baffle extending approximately around the end of the component. Alternatively, the second and third portions may be coupled by the first portion to form a v-shape. In this case, the second and third portions may extend approximately around the end of the component closest to the opening, and the first, second, and third portions may extend along the first edge. Providing a baffle extending approximately around the end of the component may block more direct lines of sight or direct sight between the exposure area and the component. Thus, this may deflect the airflow between the exposure area and the component more effectively. Thus, this may reduce the incidence of contaminants on the component.

[0015] A portion of the baffle may include a getter. That is, the baffle may include a surface that preferentially captures molecules that come into contact with it. In this case, capture may be considered to include any process that absorbs, adsorbs, chemically binds, or causes the contaminant to adhere to the baffle. The getter may include a reactive material, such as aluminum, barium, magnesium, titanium, or a rare earth element. The getter may include a surface coating applied to the baffle.

[0016] A portion of the baffle may include a flexible material. The flexible material may be compliant so that the flexible material can bend when the flexible material interacts with the second body. The portion may include, for example, a plastic material or rubber. Additionally or alternatively, a portion of the baffle may include a flexible structure. That is, the structure may be compliant so that the structure can bend when the structure interacts with the second body. For example, the baffle may include a plurality of bristles or a hollow structure. The baffle may include at least one plastic tube. A baffle including a flexible material and / or structure may minimize the impact force of a baffle-substrate collision. That is, if the baffle impacts the substrate, damage to the substrate and / or baffle may be minimized.

[0017] The projection system may further comprise a dynamic gas lock. The opening of the projection system may correspond to the opening in the dynamic gas lock. The opening may further comprise a membrane configured to allow radiation to pass through but to block gas from passing through. The dynamic gas lock may direct gas towards the substrate stage. The presence of gas between the substrate and the projection system (whether in a static or dynamic situation) provides a barrier to any contaminants migrating from the substrate. If this gas is additionally moved towards the substrate, for example by a purge gas passing through the dynamic gas lock in a direction towards the substrate, this may provide additional protection to prevent contaminants from reaching the projection system. If the movement of gas from the dynamic gas lock is further optimized, this may reduce the gas flow from the substrate to the component.

[0018] The baffle may be formed integrally with the projection system.The baffle may be formed integrally with the dynamic air lock. In this case, the baffle may include a protrusion from the dynamic air lock closest to the opening in a direction towards the substrate.

[0019] The lithographic apparatus may further comprise a supply line configured to deliver gas generally towards the substrate and / or substrate table. The supply line may be associated with the projection system and may in particular be derived from the dynamic gas lock. The gas may be hydrogen. Alternatively, the gas may be an inert gas, such as argon. The gas may be provided to form a gas curtain between the substrate and the component. The gas may provide a purge to limit a contaminant-laden gas flow from the substrate to the component.

[0020] The gas emission end of the supply line may be arranged between the opening and the component.The gas emission end may be associated with the projection system and in particular with the dynamic gas lock.

[0021] The gas emission end of the supply line can be arranged between the baffle and the component. By optimizing the gas flow relative to the baffle, this can also deflect the gas flow from the substrate to the component. In this way, this can provide additional protection to prevent contaminants from reaching the component. Providing gas near the face of the baffle closest to the component can provide increased gas pressure behind the baffle. The rear can be interpreted as between the baffle and the component. The increase in gas pressure behind the baffle can reduce the gas flow from the substrate to the component. Alternatively or in addition, the gas emission end of the supply line can be arranged at the end of the baffle closest to the substrate stage. The gas supply line can be located in the inner area of ​​the baffle. The gas supply line and the gas emission end can be configured to provide a gas flow to the substrate stage from the end of the baffle closest to the substrate stage.

[0022] The gas emission end has a gas emission end width. The gas emission end width can be measured perpendicular to the direction from the substrate to the component and the direction from the opening to the component. The gas emission end width can be defined as the extent of the gas emission end along the direction. The gas emission end can be continuous along the gas emission end width. Alternatively, the gas emission end can be discontinuous along the gas emission end width, for example, the gas emission end can include a plurality of holes, and the plurality of holes span a distance equal to the gas emission end width along the direction. The gas emission end width can be defined along a scanning direction. The component can have a component width measured parallel to the gas emission end width. The gas emission end width can be equal to or greater than the component width. Advantageously, a gas emission end having a width equal to or greater than the component width can reduce gas flow at all points between the opening and the component.

[0023] The first portion of the gas emission end may extend along a first edge of the component. The first edge may be closest to the opening. The second and third portions of the gas emission end may extend along at least a portion of the second and third edges of the component. The second and third edges may be adjacent to the first edge. The second and third edges may be perpendicular to the first edge. The gas emission end may extend approximately around the end of the component closest to the opening. For example, the first, second, and third portions may form a C-shaped gas emission end extending approximately around the end of the component. Providing a gas emission end extending approximately around the end of the component may further reduce the gas flow between the exposure area and the component. Providing a gas emission end extending approximately around the end of the component may provide a contaminant-free purge gas flow to a larger portion of the component. Thus, this may reduce the incidence of contaminants on the component.

[0024] According to a second aspect of the present invention, a method for reducing contaminants in a lithography device is provided, the method comprising: using a projection system to project a radiation beam through an opening in the projection system and onto an exposure area of ​​a substrate; and using a position monitoring system to determine the position of the substrate relative to the projection system; wherein a component of the position monitoring system is located below the projection system, and wherein a baffle is arranged between the opening and the component to deflect the airflow between the exposure area and the component.

[0025] The lithographic apparatus may be an EUV lithographic apparatus. The opening may be located at the lowermost end of the projection system. The lowermost end may be interpreted as the end of the projection system closest to the substrate. The opening may be configured to allow a radiation beam to be projected from the projection system onto the substrate. The opening may include a membrane configured to allow airflow to be prevented from passing through the opening while the radiation beam passes through the opening. The opening may be arranged below the projection system. Below may be interpreted as the end of the projection system closest to the substrate. The position monitoring system may include, for example, an interferometer or a linear encoder. The position monitoring system may generally be associated with the lithographic apparatus. A component of the position monitoring system may be arranged below the position monitoring system. The component may be closest to the opening. The component may be closest to the substrate and / or a substrate table configured to support a substrate.

[0026] The lithographic apparatus may be subject to contaminants, for example, due to degassing of resist from the substrate. Contaminants on components in the lithographic apparatus may reduce the performance and / or service life of the apparatus. Contaminants on components (such as components of the position monitoring system) may reduce the effectiveness of determining the position of the substrate relative to the projection system. Providing a baffle in the lithographic apparatus may reduce or limit the migration of contaminants from the substrate to the components. The contaminants may be gaseous. Alternatively or additionally, the contaminants may be liquid or solid and may be suspended in a gas. The contaminants may be transferred through the lithographic apparatus via a gas flow. The gas may transfer contaminant particles from the substrate to the components. The baffle may deflect or limit the gas flow within the lithographic apparatus. The baffle may deflect the gas flow from a portion of the substrate located below the opening to the component. The deflection or restriction of the gas flow may reduce the incidence of contaminant particles on the component. The baffle may block a direct line of sight or direct sight between the opening and a portion of the component. The baffle may block a direct line of sight or direct sight between the component and an area of ​​the substrate located directly below the opening. The baffle may have a cross-sectional shape that is elongated in a direction perpendicular to both a direction from the opening to the substrate and a direction from the opening to the component. The elongated shape may extend so that there is no direct line of sight or direct sight between any portion of the component and any portion of the opening.

[0027] The component may include a reflective surface, such as a reflective surface associated with an interferometric measurement system. The position monitoring system may reflect a laser beam off the reflective surface. The component may include a scale, such as a scale associated with a linear encoder. The component may include a sensor. The baffle may be provided to reduce contamination on a portion of the reflective surface, scale, or other component.

[0028] The method may also include positioning the baffle to block the line of sight between the exposure area and at least a portion of the component. The baffle may have a baffle width. The baffle width may be measured perpendicular to the direction from the substrate to the component and the direction from the opening to the component. The baffle width may be defined along a scanning direction. The component may have a component width measured parallel to the baffle width. The baffle width may be equal to or greater than the component width. The baffle may have a cross-sectional shape that is elongated in a direction perpendicular to both the direction from the opening to the substrate and the direction from the opening to the component. Advantageously, a baffle having a width equal to or greater than the component width may block all direct lines of sight or direct sight lines between the opening and the component. Blocking direct lines of sight or direct sight lines may deflect the airflow more efficiently and thereby reduce the likelihood of contaminants impacting the component.

[0029] The method may further comprise providing a baffle having a baffle height, the baffle height being defined as an extent of the baffle in a direction between the projection system and the substrate. The baffle height may be configured to block all sight lines between the exposure area and at least the first 5 cm of the component closest to the opening.

[0030] The method may also include capturing contaminant particles by providing a getter to a portion of the baffle. That is, the baffle may be provided with a surface that preferentially captures molecules that come into contact with it. In this case, capture may be considered to include any process that absorbs, adsorbs, chemically binds, or causes the contaminant to adhere to the baffle. The getter may include a reactive material, such as aluminum, barium, magnesium, titanium, or a rare earth element. The getter may include a surface coating applied to the baffle.

[0031] The method may further comprise providing an additional gas flow from the projection system generally towards the substrate. The gas flow may be provided by a gas supply line. The supply line may be associated with the projection system and may in particular originate from the dynamic gas lock. The gas may be hydrogen. Alternatively, the gas may be an inert gas, such as argon. The gas may be provided to form a gas curtain between the substrate and the component. The gas may provide a purge to limit the contaminant-carrying gas flow from the substrate to the component. The supply line may also be configured to deliver gas towards the baffle. By optimizing the gas flow relative to the baffle, this may also deflect the gas flow from the substrate to the component. In this way, this may provide additional protection to prevent contaminants from reaching the component. A portion of the gas emission end of the supply line may be arranged between the opening and the component. A portion of the gas emission end may be arranged at the end of the baffle closest to the substrate table. There may be a single supply line or there may be multiple supply lines. One or more supply lines may be arranged in an inner region of the baffle.

[0032] The projection system may be provided with a dynamic gas lock. The opening of the projection system may correspond to the opening in the dynamic gas lock. The dynamic gas lock may direct gas towards the substrate stage. The presence of gas between the substrate and the projection system (whether static or dynamic) provides a barrier to any contaminants migrating from the substrate. If this gas is additionally moved towards the substrate, for example by a purge gas passing through the dynamic gas lock in a direction towards the substrate, this may provide additional protection to prevent contaminants from reaching the projection system. If the movement of gas from the dynamic gas lock is further optimized, this may reduce the gas flow from the substrate to the component. The baffle may be formed by a portion of the dynamic gas lock. In this case, the baffle may include a protrusion from the dynamic gas lock closest to the opening in a direction towards the substrate. The gas emission end may be associated with the projection system and in particular with the dynamic gas lock.

[0033] The method may further include providing an increased gas pressure between the baffle and the component. Providing gas near the face of the baffle closest to the component may provide an increased gas pressure behind the baffle. Behind may be interpreted as between the baffle and the component. The increased gas pressure behind the baffle may reduce the gas flow from the substrate to the component.

[0034] According to a third aspect of the present invention, there is provided a device manufactured using the apparatus or method described in detail above. The device may be an integrated circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0036] - Figure 1 A lithographic system is depicted, the lithographic system comprising a lithographic apparatus and a radiation source;

[0037] - Figure 2A and Figure 2B Depicting a portion of a projection system including a baffle;

[0038] - Figure 3A and Figure 3B depicts a portion of a projection system including a baffle in an alternative arrangement;

[0039] - Figure 4A and Figure 4B depicting a portion of a projection system including a baffle in an alternative arrangement; and

[0040] Figure 5A , Figure 5B and Figure 5C A portion of the projection system including the baffle and gas supply lines is depicted. DETAILED DESCRIPTION

[0041] Figure 1 A lithographic system is shown comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and for supplying the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises 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 substrate may also be referred to as a wafer. The substrate table WT may also be referred to as a substrate support.

[0042] Figure 1The radiation source SO shown is of a type that may be referred to as a laser produced plasma (LPP) source, for example. A laser system 1 (which may, for example, include a CO2 laser) is arranged to deposit energy via a laser beam 2 into a fuel, such as tin (Sn) provided from, for example, a fuel emitter 3. Although tin is mentioned in the following description, any suitable fuel may be used. The fuel may, for example, be in liquid form and may, for example, be a metal or an alloy. The fuel emitter 3 may include a nozzle configured to direct tin, for example, in the form of droplets, along a trajectory toward a plasma formation region 4. The laser beam 2 is incident on the tin at the plasma formation region 4. The laser energy is deposited into the tin, generating a tin plasma 7 at the plasma formation region 4. During the de-excitation and recombination of electrons with ions of the plasma, radiation including EUV radiation is emitted from the plasma 7. The radiation source SO may alternatively be a discharge produced plasma (DPP) source, a free electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0043] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. The illumination system IL may include a faceted field mirror arrangement 10 and a faceted pupil mirror arrangement 11. The faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11 together provide a desired cross-sectional shape and a desired intensity distribution for the EUV radiation beam B. The illumination system IL may include other mirrors or arrangements in addition to or instead of the faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11.

[0044] After being so conditioned, the EUV radiation beam B interacts with the pattern forming device MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may include a plurality of mirrors configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate table WT. The radiation beam B' travels through an opening 16 in the projection system PS to leave the projection system PS and be projected onto a portion E of the substrate W. The portion E of the substrate W that is illuminated by the patterned radiation beam B' typically corresponds to an area of ​​the substrate W that is directly below the opening 16 and may be referred to as an exposure area E.

[0045] In normal operation, for example during exposure, a substrate W is supported on the substrate table WT. When in a suitable position, the substrate W is substantially parallel to the substrate table WT. However, it will be appreciated that in some circumstances, the substrate W may not be present. Thus, any directional language characterizing the substrate W (e.g., a direction towards the substrate W) may be considered synonymous with directional language characterizing the substrate table WT (e.g., a direction towards the substrate table WT).

[0046] For the purpose of illustrating the present invention, a Cartesian coordinate system may be used. The Cartesian coordinate system has three axes, namely 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 axes. In this description of the apparatus, the x-axis and y-axis are considered to be in the plane of the substrate table WT, and the z-axis is considered to be perpendicular to the substrate table WT, e.g. Figure 1 . The x-axis is also considered to be parallel to the direction from the opening 16 to the reflector 18. The lithographic apparatus has a scanning direction, which is considered to be the direction in which the radiation is scanned across a portion of the substrate W. In this embodiment, the scanning direction is the y-direction. It should be understood that the use of a coordinate system is illustrative and non-limiting. It will be understood that the apparatus may be oriented in different ways without departing from the scope of the present invention. For example, it will be understood that, although in the illustrated embodiment, the direction from the opening 16 to the reflector 18 is perpendicular to the scanning direction, the opening 16 and the reflector 18 may alternatively be aligned parallel to the scanning direction or in any other direction.

[0047] Directional language may also be used to explain the present invention. The projection system PS may be considered to be located "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 located "below" the projection system. Synonymously, above and below may be considered to be along Figure 1 It should be understood that the directional language is non-limiting and the device can be oriented in different ways without departing from the scope of the present invention.

[0048] The projection system PS may apply a demagnification factor to the patterned EUV radiation beam B' so as to form an image having features that are smaller than corresponding features on the patterning device MA. For example, a demagnification factor of 4 or 8 may be applied. Figure 1 1. Although illustrated in FIG. 1 as having only two mirrors 13, 14, the projection system PS may comprise a different number of mirrors (eg six or eight mirrors).

[0049] The substrate W may include a previously formed pattern. In this case, the lithographic apparatus LA aligns an image formed by the patterned EUV radiation beam B with a pattern previously formed on the substrate W.

[0050] The substrate table WT may be configured to accurately position the substrate support WT and thereby 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.

[0051] Two position monitoring systems RMS may be provided for monitoring the substrate support WT and thereby the position of the substrate W relative to the projection system PS. In the depicted example, the position monitoring system PMS comprises an interferometric measurement system. However, in an alternative embodiment, the position monitoring system PMS may be a sensor comprising a scale or a linear encoder, for example. Many position monitoring systems RMS are known in the art. Parts of the position monitoring system 18 will typically be associated with an area below the projection system PS. The part 18 may be arranged below the projection system PS and may, for example, be fixed to the bottom of the projection system PS. The part 18 may be an element of the position monitoring system PMS, such as a mirror in an interferometric measurement system or a scale in a linear encoder. The part may be a sensor. The purpose of the part 18 may be to provide a reference surface associated with the projection system PS and thereby help determine the position of the substrate table WT relative to the projection system. In the depicted example, the present invention will be described with respect to an interferometric measurement system PMS comprising a mirror 18. However, this should not be seen as limiting, and it should be understood that the mirror 18 may be replaced by different components of the position monitoring system PMS without departing from the scope of the present invention.

[0052] In the depicted example, each position monitoring system RMS comprises a reflective surface 18. The reflective surface 18 may also be referred to as a mirror or positioning mirror 18. The mirror 18 may be arranged below the projection system PS. The mirror 18 may be configured to receive and reflect a coherent light source (e.g. a laser beam L), which may be used to determine the displacement of the substrate table WT and thereby the substrate W relative to the projection system PS.

[0053] The reflector 18 may be associated with the projection system PS. The reflector 18 may be fixed to the projection system PS. Alternatively, the reflector 18 may be associated with the substrate table WT. The reflector 18 may be fixed to the substrate table WT. The reflector 18 may be associated with the projection system PS or the substrate table WT via additional system components. For example, a frame may be provided to which the reflector 18 and the projection system PS and / or the substrate table WT may be mounted, for example using air mounts.

[0054] In the depicted example, the mirror 18 is associated with the projection system PS. In operation, a laser beam L may be generated by a laser LA. The laser beam L may be directed to a beam splitter arrangement. The beam splitter arrangement may include a beam splitter BS to split the laser beam L into a first part and a second part. The beam splitter arrangement may also include at least one mirror 17 to direct the first part of the laser beam L to a detector DE. The second part of the laser beam L may be directed to a 45° mirror M1, which is fixedly connected to the substrate table WT in a manner that it is at an angle of 45° relative to the xy plane. It will be appreciated that the selection of an angle of 45° for the 45° mirror M1 is suitable for the depicted device, but other geometries may be selected, such as a 30° mirror or a mirror at any other angle. The 45° mirror M1 is configured to direct the second part of the laser beam L to the mirror 18. The mirror 18 reflects the second part back to the 45° mirror M1 which can then direct the second part towards the photodetector. The photodetector can then use interferometry to determine the phase shift between the first and second parts of the laser beam L to determine the displacement of the substrate table WT relative to the projection system PS.

[0055] In the depicted example, two position monitoring systems RMS are shown, each of which includes a positioning mirror 18. However, a different number of position monitoring systems can be used. For example, a single position monitoring system RMS or four position monitoring systems RMS. The depicted example shows a preferred arrangement for determining the displacement of the substrate W along the z direction. Position monitoring systems and mirrors can also be used to determine the displacement of the substrate W along the x-direction and the y-direction. A relative vacuum can be provided in the projection system PS, that is, a small amount of gas (for example, hydrogen) at a pressure far below atmospheric pressure. The area around the substrate W is at ambient pressure. The area around the substrate W can be defined as the area roughly between the substrate table WT and the end of the projection system PS closest to the substrate table WT. This area can also be referred to as a chamber.

[0056] In a manufacturing process using a lithographic apparatus, a pattern is imaged onto a substrate W, which is at least partially covered in a layer of radiation-sensitive material (also referred to as a photoresist). The pattern is imaged onto a patterned radiation beam B' by exposing the substrate W, whereby the incident radiation chemically alters the photoresist so that subsequent processing techniques can be used to remove one or more portions of the photoresist determined by the pattern. Exposure of the photoresist can result in the release of compounds (e.g., volatile organic compounds, such as hydrocarbons). The release of compounds due to exposure of the photoresist can also be referred to as degassing. Compounds released by degassing can be referred to as degassing compounds. Additionally or alternatively, degassing compounds can be released without exposure of the photoresist. That is, degassing can occur spontaneously.

[0057] The degassing compound may be gaseous. Alternatively, the degassing compound may be solid or liquid and may be suspended in a gas. The degassing compound may be transported around the lithographic apparatus via a gas flow path. The degassing compound may also be referred to as a contaminant.

[0058] Outgassing may be disadvantageous because the outgassing compounds may adhere to other components within the lithographic apparatus, causing contamination. In particular, contaminants may adhere to the mirror 18 because the mirror 18 is close to the area of ​​the substrate W located below the opening 16, i.e. the exposure area of ​​the substrate W.

[0059] Contaminants on the reflector 18 may significantly reduce the accuracy of the position monitoring system PMS. Accurate position monitoring facilitates optimal operation of the lithographic apparatus. For example, accurate position monitoring facilitates achieving positional accuracy of exposure and thereby high resolution exposure and overlay. As the amount of contaminants on the reflector 18 increases, the performance of the lithographic apparatus may deteriorate. As contaminants on the reflector 18 continue to accumulate, the performance of the lithographic apparatus may deteriorate over time.

[0060] Contaminants on the reflector 18 may significantly reduce the service life of the position monitoring system PMS. As more contaminants adhere to the reflector 18, the performance of the position monitoring system PMS and thus the performance of the lithographic apparatus may be lower than the performance requirements of the user. When the reflector 18 is significantly covered with contaminants, it may be necessary to replace or clean the reflector. Cleaning can be performed manually, but this may be invasive and may require downtime in the lithographic process. Downtime in the lithographic process causes loss of production time and thus reduces the output of the lithographic process. Cleaning can be automated and performed, for example, by chemical methods (such as hydrogen radical generation) or by active heating. However, these automated cleaning methods may be difficult to implement, because the space available in this part of the lithographic apparatus is very limited. In addition, these automated cleaning methods may deposit heat and damage the substrate W or the lithographic apparatus. The reflector 18 can be replaced, but this may be expensive and may require downtime in the lithographic process when replacement occurs. On the contrary, it is advantageous to reduce the possibility of contaminants hitting optical elements in the lithographic apparatus.

[0061] The present invention reduces contaminants on the reflector 18 by arranging a baffle 19 between the opening 16 and the reflector 18. The baffle 19 is provided to deflect the airflow between the exposure area E of the substrate W (i.e., the area of ​​the substrate W located below the opening 16) and the reflector 18. The baffle 19 can block the direct line of sight or direct line of sight between the exposure area E and the reflector 18. As a result, many airflow paths from the exposure area E to the reflector 18 are blocked by the baffle 19 and the airflow is deflected thereby. The airflow may include contaminants, so deflecting the airflow may result in the deflection of contaminants. Therefore, the use of the baffle 19 can reduce the possibility of contaminants hitting the reflector 18.

[0062] Although reference may be made herein to gas flow and / or contaminants from the substrate W to the mirror 18, this may be interpreted as gas flow and / or contaminants from the exposure region E of the substrate W. Contaminants are typically released in response to incident radiation B′ travelling through the opening 16 and onto the exposure region E of the substrate W.

[0063] Optimisation of the surrounding area and the size, shape and position of the baffle 19 may increase its effectiveness in reducing the likelihood of contaminants striking the reflector 18. Some example arrangements are described in more detail further below.

[0064] In some exemplary implementations, a dynamic gas lock (DGL) may be provided to reduce any gas flow from the substrate W to the projection system PS. The DGL may direct gas towards the substrate table. The gas flow from the projection system PS towards the substrate table WT provides a barrier to any contaminants that migrate from the substrate W into the projection system. The DGL may include a membrane that is substantially transparent to radiation but blocks gas flow into the projection system PS. In this case, the gas flow from the DGL will prevent or reduce the accumulation of contaminants on the membrane. However, the gas flow from the DGL may introduce additional gas flow pathways, which may increase the likelihood of contaminants migrating from the substrate W to the reflector 18. Thus, in an apparatus utilizing a DGL, the use of a baffle 19 is particularly advantageous for deflecting the gas flow from the substrate W and the reflector 18 and thereby reducing the impact of contaminants on the lithographic apparatus.

[0065] Some exemplary embodiments of a lithographic apparatus including a baffle 19 between the opening 16 and the mirror 18 will now be described with reference to FIGS. 2 to 5 .

[0066] Figure 2A and Figure 2B A portion of a projection system PS and a substrate table WT according to an embodiment of the present invention is depicted. The projection system PS comprises an opening 16 through which radiation leaves the projection system PS. The opening 16 is schematically depicted as a rectangle, but it will be appreciated that this is illustrative and non-limiting and that openings of other shapes may be used. For example, the opening may be curved. The projection system PS also comprises two mirrors 18 associated with two position monitoring systems. For simplicity, other components of the position monitoring systems are not shown.

[0067] A substrate W is positioned on a substrate table WT below the projection system PS. The substrate W has an exposure area E, which is defined as an area of ​​the substrate W located below the opening 16. That is, the exposure area E is an area of ​​the substrate W that is configured to receive radiation when the photolithography process is in operation. A degassing compound 21 is shown, which has been released from the surface of the substrate W, for example after exposure of a resist on the substrate W.

[0068] The arrow diagram shows possible gas flow paths in the lithographic apparatus. If the baffle 19 is not present, the gas flow will be isotropic around the exposure area E. As a result, the contaminants carried in the gas will travel in all directions and in particular will travel towards the reflector 18. An unimpeded gas flow along the x-direction can allow the outgassing compound 21 to migrate from the substrate W towards the reflector 18. In practice, unless the gas flow path is deflected, contaminants can be deposited around the opening 16 in all directions. For example, contaminants can be deposited in a ring around the opening 16 and on the ring-covered portion of the reflector 18.

[0069] In this embodiment, a baffle 19 is placed between the opening 16 and each reflector 18 (i.e., two baffles 19 are provided). The baffles 19 are positioned to deflect or restrict the gas flow within the lithographic apparatus. In particular, the baffles 19 are positioned to deflect the gas flow traveling from the exposure area E toward the reflector 18. It can be seen that the gas flow in the x-direction is obstructed by the baffles 19. In this way, any contaminants carried by the gas will be less likely to travel to and adhere to the reflector 18. The baffles 19 therefore reduce the likelihood of contaminant particles 21 being incident on the reflector 18.

[0070] The baffle 19 can be optimized by configuring the baffle 19 so that a portion of the baffle acts as a getter. Getters are known in the art and preferentially capture molecules that come into contact with them. Getters are particularly used in lower pressure environments to capture unwanted (i.e., contaminant) compounds. In this case, capture can be considered to include any process of absorbing, adsorbing, chemically binding, or causing the contaminant to adhere to the getter. The use of a getter in combination with the baffle 19 can also reduce the likelihood of contaminants reaching the reflector 18. Many getters are known in the art, for example, the getter can include reactive substances such as aluminum, barium, magnesium, titanium, or rare earth elements. The getter can be a portion of the baffle 19, or the entire baffle 19 can include a getter. The getter can be a surface coating on the baffle 19.

[0071] Although two baffles 19 are provided in this embodiment, a different number of baffles may be provided in other embodiments. For example, a lithographic apparatus comprising a position monitoring system RMS having a mirror 18 may require only one baffle 19. Providing the same number of baffles 19 as mirrors 18 may be advantageous.

[0072] The baffle 19 may have a baffle height H, which is defined as the distance from the end of the baffle 19 closest to the substrate table WT to the end of the baffle 19 closest to the projection system PS. If the baffle 19 is directly attached to the projection system PS, the baffle height H is the distance from the end of the baffle 19 closest to the substrate table WT to the projection system PS. In the example shown, the baffle height H is the extent of the baffle 19 along the z-direction.

[0073] The baffle 19 may have a baffle width Wb, which is defined as the extent of the baffle 19 along the y direction. The baffle 19 may have a baffle thickness T, which is defined as the extent of the baffle 19 along the x direction.

[0074] The baffle 19 may block a direct line of sight or a direct line of sight between the exposure area E and the reflector 18. The baffle 19 may extend along an edge of the reflector 18 closest to the opening 16. The reflector 18 may have a reflector width Wm. Advantageously, the baffle 19 may have a baffle width Wb that is equal to or greater than the reflector width Wm. The baffle 19 may extend beyond the edge of the reflector 18. A baffle width Wb greater than the reflector width Wm may allow the baffle 19 to block more of the line of sight between the exposure area E and the reflector 18.

[0075] The gas deflected by the baffle 19 may flow around the edge of the baffle 19. The baffle width Wb being greater than the reflector width Wm may reduce the amount of gas surrounding the baffle 19. The baffle width Wb being greater than the reflector width Wm may prevent the gas flowing around the edge of the baffle 19 from subsequently flowing on the reflector 18.

[0076] The baffle 19 is arranged between the projection system PS and the substrate table WT, which typically supports a substrate W. In this way, the baffle 19 has a defined space in which it can reside. This space may be referred to as a chamber. The chamber has a chamber height C', which is defined as the distance measured in the z-direction between the substrate table WT and the end of the projection system PS closest to the substrate table WT.

[0077] There are movements and tolerances associated with the lithographic process, and as such, the chamber height C' may be varied during use. For example, in order to change the focus of radiation during a lithographic exposure, the substrate table WT may be moved in the z-direction, which may alter the chamber height C'. Thus, there is a range of chamber heights C' that may exist during normal use of the lithographic apparatus. When considering the chamber height C' and the gap C, it will be appreciated that in normal operation, a substrate W will be supported on the substrate table WT. As a result, the distance between the substrate W and the baffle 19 will be less than the chamber height C'. The gap C may be large enough so that during normal operation of the lithographic apparatus in the presence of a substrate W, the baffle 19 will not contact the substrate W. Normal operation may include planned events, such as lithographic exposure and scanning. Normal operation may include uncontrolled events, such as earthquakes.

[0078] An earthquake may occur when the lithographic apparatus is in use. This may cause the substrate table W to move further toward the projection system PS than during normal use of the lithographic apparatus. In this way, there is a risk that the movement of the substrate table WT may cause the baffle 19 to hit the substrate W. The same situation may also apply if the lithographic apparatus fails. Any impact between the baffle 19 and the substrate W may damage the baffle 19 and / or the substrate W. For example, in the case where the lithographic process needs to be repeated, damage to the substrate may result in reduced quality output and / or may result in a time penalty. If the substrate W breaks, the substrate W may shatter and release additional contaminant compounds into the lithographic apparatus, so the lithographic apparatus may need to be cleaned. The gap C can reduce the possibility of impact or collision. However, the possibility of impact may not be completely eliminated.

[0079] In order to increase the effectiveness of the baffle 19 in deflecting the gas flow, it may be beneficial to provide the baffle 19 with a larger baffle height H. This is because an increased baffle height H may block more direct or direct sight lines between the exposure area E and the reflector 18. If the baffle height H is too small, gas may be able to flow from the exposure area E to the reflector 18 unimpeded. The baffle 19 may block some direct or direct sight lines between the exposure area E and the reflector 18. Advantageously, the baffle 19 may be provided with a baffle height H that is large enough to block all sight lines between the exposure area and a portion of the reflector 18.

[0080] However, the increased baffle height H results in a smaller gap C. If the gap C is too small, the risk of collision may increase. The gap C may, for example, be greater than 3 mm. A gap C greater than 3 mm may advantageously reduce the risk of collision between a conventional substrate and the baffle 19. It should be understood that the gap C greater than 3 mm is calculated using the thickness of a conventional substrate. A conventional substrate may have a thickness of approximately 775 microns. For example, due to uneven thickness, the thickness of the substrate W may vary in the plane of the substrate. The gap C may take into account the thickness of the substrate W. A larger gap C may be beneficial with a thicker substrate W. In other cases, such as in locations with less earthquake risk, a gap C less than 3 mm may be sufficient.

[0081] It will be appreciated that in different lithographic apparatuses, for example in the case of different chamber heights H' or different focusing conditions, different baffle heights H and baffle gaps C may be advantageous. Thus, the baffle height H and gap C may be selected to suit the user. The baffle height H may be considered to be related to the chamber height C'. For example, the baffle ratio of the baffle height H to the chamber height C' may be calculated as H / C. A baffle ratio exceeding 20% ​​may be advantageous for deflecting the airflow from the exposure region E to the reflector 18.

[0082] Alternatively, the baffle height H may be considered in terms of its ability to block the line of sight (and thus, its ability to deflect airflow along the line of sight). For example, the baffle height H may be configured such that the baffle height H blocks all direct or direct lines of sight between the exposure area E and a portion of the reflector 18. This portion may be the area of ​​the reflector 18 that would receive most contaminants in the absence of the baffle 19. It should be understood that the size of this area may vary depending on the lithographic apparatus and / or process. In an exemplary embodiment, the baffle height H may be provided to block the line of sight between the exposure area E and the first 5 cm of the reflector 18 closest to the opening. It should be understood that for other lithographic processes, it may be beneficial to block the line of sight to the component at a larger or smaller distance (e.g., but not limited to, 2 cm or 10 cm).

[0083] In order to reduce the impact of the impact, the baffle 19 or a part of the baffle 19 may include a flexible material. The flexible material may be compliant so that when the flexible material interacts with the second body, the flexible material can bend. In this way, if the baffle 19 hits the substrate W, the damage to the substrate W and / or the baffle 19 can be minimized. The flexible material may be, for example, a plastic material or rubber. In addition or alternatively, a part of the baffle 19 may include a flexible structure, such as a plurality of fine bristles, or a hollow structure (such as one or more plastic tubes). If a plastic tube is used, the plastic tube may be oriented vertically, i.e., extending from the projection system PS to the substrate W. A flexible structure may be interpreted as a structure that is designed to be compliant so that when the structure interacts with the second body, the structure can bend. It will be appreciated that, although compliant materials and / or structures may be beneficial, the stiffness of the baffle 19 is still sufficient to deflect the airflow. That is, the structure may bend when in contact with the substrate W, but may remain substantially undeformed when gas is flowed towards the structure in the lithographic apparatus.

[0084] exist Figure 2A and Figure 2B In the example depicted in , the baffle 19 is in the shape of a cuboid. This shape advantageously provides a barrier for deflecting the airflow. However, the shape of the baffle 19 can be optimized to control the airflow within the chamber. For example, eddies can be reduced by providing a baffle with curved edges. Some examples of alternative baffle shapes are described below with respect to FIGS. 3 and 4.

[0085] Figure 3A and Figure 3B A baffle 19 is depicted having a horizontal portion 19a and a vertical portion 19b. Here, the baffle extends a considerable length in the x-direction before extending downward in the z-direction. In this case, the baffle shape is generally L-shaped. In particular, a curved portion 19c couples the horizontal portion 19a and the vertical portion 19b together. This shape can be beneficial for manufacturing purposes.

[0086] In this example, the projection system PS also includes a dynamic gas lock (DGL) 20. As mentioned above, the DGL 20 can direct gas towards the substrate table WT, such as by Figure 3A. The DGL 20 is provided with gas via a supply line which may originate from another part of the projection system PS or an external source (not shown). The DGL 20 is provided to reduce the likelihood of gas travelling upwards into the projection system PS and to provide a barrier to any contaminants 21 migrating from the substrate W to the projection system PS. In an apparatus utilising the DGL 20, the use of a baffle 19 is particularly advantageous. This is because there is an additional gas flow path and the baffle 19 may advantageously deflect a gas flow carrying contaminants and thereby reduce the effect of contaminants on the lithographic apparatus. When a baffle 19 in combination with a DGL 20 is used, the baffle 19 or a portion of the baffles 19a, 19b, 19c may be formed integrally with the DGL 20.

[0087] exist Figure 4A and Figure 4B 16. Another alternative baffle shape is depicted in FIG. 17. In this embodiment, the baffle 19 is curved when viewed from below. The baffle 19 may extend along its proximal edge 18a of the reflector 18 (the proximal edge 18a of the reflector 18 being the edge closest to the opening 16). Due to its curvature, the baffle 19 may also extend partially along the adjacent side edges 18b, 18c of the reflector 18. Advantageously, this shape partially surrounds the end of the reflector 18 closest to the opening 16. Partially surrounding the end of the reflector 18 blocks more of the direct line of sight or direct line of sight between the substrate W and the reflector 18. This further reduces the likelihood of contaminants striking the reflector 18. It will be appreciated that while a C-shape has been illustrated here, a similar effect may be achieved using another shape of baffle 19 that extends around the side edges 18b, 18c of the reflector 18 adjacent to the proximal end of the reflector.

[0088] Alternatively, the baffle 19 can be shaped so that the baffle 19 is "v-shaped" when viewed from below. That is, a single baffle 19 can include a first straight portion and a second straight portion joined together at a first end of the first portion and a first end of the second portion, wherein the joined portions are parallel at an angle such that the first portion and the second portion form a V-shaped pattern or v-shape. The angle can be altered to form a narrower or wider v-shape. The v-shaped baffle 19 can beneficially deflect airflow from the reflector 18. The v-shaped baffle 19 can extend generally around adjacent sides 18b, 18c of the reflector 18 and thereby partially surround the end of the reflector 18 closest to the opening 16.

[0089] Figure 4A and Figure 4BThe projection system PS in FIG. 1 further comprises a DGL 20. In some cases, the use of the DGL 20 in conjunction with the baffle 19 may be beneficial. In particular, the gas flow from the DGL 20 may be further optimized relative to the baffle 19, which may help further deflect the gas flow from the substrate W to the reflector 18. In addition, the gas supply line may already exist in the DGL component, so that it is feasible to implement a new gas supply path. FIG. 5A to FIG. 5C Some example implementations of optimizing airflow are described.

[0090] FIG. 5A to FIG. 5C The projection system PS in 1 comprises two baffles 19 and two gas supply lines 22. The gas supply lines 22 are configured to deliver gas generally toward the substrate W and / or the substrate table WT. Such gas can form a gas curtain between the substrate W and the reflector 18, and thereby reduce the airflow carrying contaminants from the substrate W to the reflector 18. This can also be referred to as local purge, purge flow or purge gas flow. The local purge can help deflect the airflow from the substrate W to the reflector 18. The local purge can also ensure that clean (i.e., contaminant-free) gas flows on the reflector 18, which further reduces the possibility of contaminants adhering to the reflector 18. The purge gas can displace the gas carrying contaminants near the reflector 18.

[0091] In the depicted example, the gas is provided 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, by a delivery tube attached to the bottom side of the projection system PS. If a gas supply line 22 is used, there may be the same number of supply lines 22 as baffles 19 or mirrors 18. For example, if only one baffle 19 is used, there may be one supply line 22. Alternatively, one supply line may be used to supply gas flow near multiple baffles. Alternatively, there may be multiple supply lines 22. Where there are multiple supply lines 22, it may be configured so that there are multiple supply lines associated with a single baffle 19, or multiple supply lines associated with multiple baffles. The gas may be hydrogen. The use of hydrogen may be advantageous as hydrogen has been used in some known photolithography processes. The gas may be non-reactive, for example an inert gas such as argon. Argon may be advantageously used because it is a heavier molecule than hydrogen and may provide a greater degree of rejection of outgassing compounds. However, argon may be less readily available and / or more expensive than hydrogen.

[0092] The supply line 22 may include a gas emission end 24. The gas in the supply line 22 may enter the chamber below the projection system PS from the gas emission end 24. The gas emission end 24 of the supply line 22 may be configured so that the gas flow is provided between the ends of the baffle 19 closest to the substrate table WT or substrate W. For example, the gas supply line 22 may be arranged inside the baffle 19. The gas emission end 24 of the supply line may be located at the end of the baffle 19 closest to the substrate table WT. In this way, injecting gas into the baffle 19 via the gas supply line 22 may cause the gas to flow downward from the end of the baffle 19 and towards the substrate table WT. The gas flow at the end of the baffle 19 may reduce the gas flow from the exposure area E to the mirror 18.

[0093] Alternatively or additionally, a gas emission end 24 of the supply line 22 may be arranged between the opening 16 and the reflector 18. In particular, the supply line 22 may be configured to deliver gas near the face 19a of the baffle 19 closest to the reflector 18. This may be achieved by providing the gas emission end 24 of the supply line between the baffle 19 and the reflector 18. The gas emission end 24 and the supply line 22 may be directed such that they cooperate to direct gas near the face 19a of the baffle 19 closest to the reflector 18. In this case, the gas is still directed downwards, i.e. from the projection system PS towards the substrate W, but may be directed such that the gas travels downwards along this face 19a of the baffle 19. Providing gas near this face 19a may provide an increased gas pressure in the region between the baffle 19 and the reflector 18. The increased gas pressure in this region may reduce the gas flow from the exposure area E to the reflector 18 due to the pressure difference.

[0094] The gas supply line 22 may be used in conjunction with the use of the baffle 19. This may be advantageous because it represents an effective way to reduce the likelihood of contaminants striking the reflector 18. This is because the baffle 19 may deflect the gas flow between the exposure region E and the reflector 18, and the gas supply line 22 may also reduce the gas flow between the exposure region E and the reflector, as well as provide a purge flow of contaminant-free gas. In another example, the gas supply line 22 may be used without the baffle 19. For example, when the baffle is not present, the gas emission end 24 of the gas supply line 22 may be disposed between the opening 16 and the reflector 18. The provision of the gas emission end 24 of the supply line 22 between the opening 16 and the reflector 18 may provide a gas curtain that may reduce the gas flow from the exposure region E to the reflector 18. In addition, by providing a contaminant-free gas flow over the reflector 18 without the use of the baffle 19, the provision of the gas purge flow may be significantly sufficient to satisfactorily reduce the likelihood of contaminants striking the reflector 18. However, it is preferred to use the gas supply line 22 in combination with the baffle 19 to achieve more effective reduction of contamination of the lithographic apparatus.

[0095] The arrangement of the gas emission end 24 of the supply line 22 may be selected to advantageously control the flow of purge gas. Figure 5B and Figure 5C 2. In these examples, the baffle 19 is shaped in a manner similar to that of FIG. 2, but it will be appreciated that any shape or size of baffle 19 may be used with the gas supply line 22.

[0096] exist Figure 5B In the arrangement shown in , the cross-section of the gas emission end 24 is elongated. The elongated gas emission end 24 may also be referred to as a slot. In particular, the elongated shape extends along the y-direction. The elongated width Wg of the gas emission end 24 may be equal to or greater than the reflector width Wm. This may be advantageous because it may provide a gas curtain along the entire range of the reflector 18 in the y-direction. This may also provide a contaminant-free purge flow to more areas of the reflector 18, thereby further reducing the risk of contaminants adhering to the reflector 18. The elongated width Wg of the gas emission end 24 may be equal to or greater than the baffle width Wb. This may be advantageous because it may reduce the airflow at all points between the baffle 19 and the reflector 18.

[0097] In addition to the elongated gas-emitting tip, Figure 5CAn alternative arrangement is shown in . This example utilizes a gas emitting tip 24 that includes a plurality of holes. In this example, the plurality of holes 24 are arranged in a line so that the plurality of holes 24 form an elongated row of holes 24 extending along the y-direction. A row of holes can be beneficial because such holes are easier to manufacture than elongated slots. Similar to Figure 5B In the example in FIG. 1 , it may be advantageous that the row of holes 24 extends a width equal to or greater than the width Wm of the reflector. This may be advantageous because this may provide an air curtain along the entire extent of the reflector 18 in the y direction. This may also provide a contaminant-free purge flow to more areas of the reflector 18, thereby further reducing the risk of contaminants adhering to the reflector 18. The row of holes 24 may extend a width equal to or greater than the baffle width Wb. This may be advantageous because this may reduce the airflow at all points between the baffle 19 and the reflector 18. Four holes are shown in the depicted example, but any number of holes may be used. In this example, the row of holes 24 extends along a first side of the reflector 18.

[0098] exist Figure 5B and Figure 5C In the arrangement depicted in FIG. 1 , the gas emitting end 24 extends along the edge 18a of the reflector 18 closest to the opening 16. It may be beneficial to configure the gas emitting end 24 to extend further along a portion of the adjacent side edges 18b, 18c of the reflector 18. For example, similar to FIG. 3A to FIG. 3B 1, the gas emitting end 24 may be curved so that the gas emitting end 24 extends generally around the end of the reflector 18 closest to the opening 16. In the case of extending around the end of the reflector 18, the gas emitting end 24 may advantageously create a more efficient barrier, thereby shielding a larger portion of the reflector 18 from contaminants traveling from the substrate W. In the case of extending around the end of the reflector 18, the gas emitting end 24 may advantageously provide a contaminant-free purge gas flow to a larger area of ​​the reflector 18.

[0099] The term "projection system" PS used herein should be broadly interpreted as covering various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems or any combination thereof as appropriate to the exposure radiation used.

[0100] Although specific reference may be made herein to the use of lithographic apparatus in IC manufacturing, 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, and the like.

[0101] Although specific reference is made herein to embodiments of the invention in the context of lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of mask inspection equipment, metrology equipment, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses may generally be referred to as lithographic tools.

[0102] Although specific embodiments of the present invention have been described above, it will be appreciated that the present invention may be practiced in a manner different from that described. The above description is intended to be exemplary rather than restrictive. Therefore, it will be appreciated by those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

[0103] Aspect 1. A lithography device comprises: a projection system, which is configured to project a radiation beam through an opening in the projection system and onto a substrate; a position monitoring system, which is configured to determine the position of the substrate relative to the projection system, wherein a component of the position monitoring system is located below the projection system; and a baffle, which is arranged between the opening and the component.

[0104] Aspect 2. The lithographic apparatus according to aspect 1, wherein the component comprises a reflective surface of an interferometer or a scale of a linear encoder.

[0105] Aspect 3. The lithographic apparatus according to aspect 1 or 2, wherein the baffle has a baffle width, the feature has a feature width measured parallel to the baffle width, and the baffle width is equal to or greater than the feature width.

[0106] Aspect 4. The lithographic apparatus according to any preceding aspect, further comprising a substrate table configured to support the substrate, wherein the baffle comprises a substantially vertical portion extending in a direction substantially between the projection system and the substrate table.

[0107] Aspect 5. A lithographic device according to any preceding aspect, wherein the first portion of the baffle extends along a first edge of the component closest to the opening, and the second and third portions of the baffle extend along at least a portion of a second and third edges of the component, wherein the second and third edges are adjacent to the first edge.

[0108] Aspect 6. The lithographic apparatus according to any preceding aspect, wherein a portion of the baffle comprises a getter.

[0109] Aspect 7. The lithographic apparatus according to any preceding aspect, wherein a portion of the baffle comprises a flexible material.

[0110] Aspect 8. The disclosed apparatus according to any preceding aspect, wherein the projection system further comprises a dynamic air lock, and wherein the opening of the projection system corresponds to the opening in the dynamic air lock.

[0111] Aspect 9. The lithographic apparatus according to any preceding aspect, wherein the baffle is formed integrally with the projection system.

[0112] Aspect 10. The lithographic apparatus according to any preceding aspect, further comprising a supply line configured to deliver a gas substantially towards the substrate.

[0113] Aspect 11. A method for reducing contaminants in a lithography device, the method comprising: using a projection system to project a radiation beam through an opening in the projection system and onto an exposure area of ​​a substrate; and using a position monitoring system to determine the position of the substrate relative to the projection system, wherein a component of the position monitoring system is located below the projection system; wherein a baffle is disposed between the opening and the component to deflect the airflow between the exposure area and the component.

[0114] Aspect 12. The method according to aspect 11, wherein the component comprises a reflective surface of an interferometer or a scale of a linear encoder.

[0115] Aspect 13. The method according to aspect 11 or 12, wherein the baffle is positioned to block the line of sight between the exposure area and at least a portion of the component.

[0116] Aspect 14. A method according to any one of Aspects 11 to 13, wherein the baffle is provided with a baffle height, the baffle height being defined as the extent of the baffle along a direction between the projection system and the substrate, and the baffle height being configured to block all sight lines between the exposure area and at least the first 5 cm of the component closest to the opening.

[0117] Aspect 15. The method according to any one of aspects 11 to 14, further comprising capturing contaminant particles with a getter.

[0118] Aspect 16. The method according to any one of aspects 11 to 15, further comprising providing an additional gas flow from the projection system towards the substrate.

[0119] Aspect 17. The method of aspect 16, further comprising providing an increased gas pressure between the baffle and the portion of the position monitoring system.

[0120] Aspect 18. A device manufactured using the apparatus according to any one of aspects 1 to 10 or the method according to any one of aspects 11 to 17.

Claims

1. A pollutant reduction device comprising: a position monitoring system configured to determine a position of the substrate relative to a projection system configured to project a radiation beam through an opening in the projection system and onto the substrate, wherein components of the position monitoring system are located below the projection system when in use; and A baffle is disposed between the opening and the component, wherein the component comprises a reflective surface of an interferometer or a scale of a linear encoder.

2. The pollutant reduction device according to claim 1, wherein: The baffle has a baffle width, the component has a component width measured parallel to the baffle width, and the baffle width is equal to or greater than the component width.

3. A contamination reduction apparatus according to any preceding claim, further comprising a substrate table configured to support the substrate, wherein the baffle comprises a substantially vertical portion extending in a direction substantially between the projection system and the substrate table.

4. A pollutant reduction device according to any preceding claim, wherein: The first portion of the baffle extends along a first edge of the component proximate the opening, and the second and third portions of the baffle extend along at least a portion of second and third edges of the component, wherein the second and third edges are adjacent to the first edge.

5. A pollutant reduction device according to any preceding claim, wherein: A portion of the baffle includes a getter and / or a flexible material.

6. A pollutant reduction device according to any preceding claim, wherein: The projection system further comprises a dynamic air lock, and wherein the opening of the projection system corresponds to the opening in the dynamic air lock.

7. A pollutant reduction device according to any preceding claim, wherein: The baffle is integrally formed with the projection system.

8. A contamination reduction apparatus according to any preceding claim, further comprising a supply line configured to deliver gas generally towards the substrate.

9. The pollutant reduction device of claim 8, wherein: The gas emission end of the supply line is disposed between the opening and the component of the position monitoring system.

10. The pollutant reduction device of claim 9, wherein: The gas emission end of the supply line is disposed between the baffle and the component of the position monitoring system.

11. A pollutant reduction device according to claim 9 or 10, wherein: The gas emitting tip has a gas emitting tip width, the component of the position monitoring system has a component width measured parallel to the gas emitting tip width, and the gas emitting tip width is equal to or greater than the component width.

12. A pollutant reduction device according to any one of claims 9 to 11, wherein: A first portion of the gas emitting tip extends along a first edge of the component proximate the opening, and second and third portions of the gas emitting tip extend along second and third edges of the component, wherein the second and third edges are adjacent to the first edge.

13. A lithographic apparatus comprising a contamination reduction apparatus according to any preceding claim.

14. A method for reducing pollutants in a device, the method comprising: projecting a radiation beam through an opening in the projection system and onto an exposure area of ​​the substrate using a projection system; as well as determining a position of the substrate relative to the projection system using a position monitoring system, wherein components of the position monitoring system are located below the projection system; wherein a baffle is disposed between the opening and the component to deflect airflow between the exposure area and the component, and wherein the component comprises a reflective surface of an interferometer or a scale of a linear encoder.

15. A device manufactured using the contamination reduction apparatus of any one of claims 1 to 12 or the lithographic apparatus of claim 13 or the method of claim 14.

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