Pollution control

Abstract

A lithographic patterning device contamination control assembly includes: a support structure configured to support a patterning device that floats relative to ground; a shielding device configured to selectively shield the lithographic patterning device, the shielding device being connected to a ground; the apparatus includes a mask apparatus, a lithographic patterning apparatus, a gas supply, and an ionization apparatus, the gas supply configured to supply a gas to the ionization apparatus, and the ionization apparatus configured to convert the gas into a quasi-neutral plasma located in a region between the mask apparatus and the lithographic patterning apparatus.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to European application 22206094.9, filed on November 8, 2022, and the entire content of the European application is incorporated herein by reference. Technical field

[0003] The present invention relates to contamination control in a lithographic apparatus. Background art

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

[0005] To project a pattern onto a substrate, a lithographic apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features that can be formed on the substrate. Compared to a lithographic apparatus that uses radiation having a deep ultraviolet (DUV) wavelength of, for example, 193 nm, a lithographic apparatus that uses extreme ultraviolet (EUV) radiation having a wavelength in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0006] In a conventional (DUV) lithographic apparatus, a pellicle is attached to the patterning device. The pellicle is a diaphragm that is spatially separated from the patterning device. When contamination particles incident on the pellicle are projected onto the substrate by the lithographic apparatus, the contamination particles will be out of focus. Thus, the contamination particles do not introduce defects into the pattern projected from the patterning device to the substrate by the lithographic apparatus.

[0007] A pellicle can also be used in an EUV lithographic apparatus. However, EUV radiation is absorbed by the pellicle, and this reduces the intensity of the EUV radiation that can be used to expose the substrate. This in turn also reduces the throughput of the lithographic apparatus.

[0008] It may be desirable to provide an apparatus that overcomes or alleviates one or more problems associated with the prior art. Summary of the invention

[0009] According to a first aspect of the present invention, there is provided a contamination control assembly for a lithographic patterning apparatus, comprising: a support structure configured to support a patterning apparatus, the patterning apparatus being floating relative to ground; a shielding device configured to selectively shield the lithographic patterning apparatus, the shielding device being connected to ground; a gas supply and an ionization device, the gas supply being configured to supply gas to the ionization device, and the ionization device being configured to convert the gas into a quasi-neutral plasma, the quasi-neutral plasma being located in a region between the shielding device and the lithographic patterning apparatus.

[0010] Advantageously, there is substantially no electric field within the quasi-neutral plasma and thus charged contamination particles are not accelerated towards the patterning apparatus. Alternatively, the charged contamination particles may remain within the quasi-neutral plasma.

[0011] The assembly may further comprise a gas removal system configured to remove gas from a housing within which the support structure and the shielding device are located.

[0012] The term "gas removal" may include plasma removal.

[0013] The gas removal system may be located on a side of the EUV radiation exposure zone opposite to the gas supply system.

[0014] The shielding device may comprise blades.

[0015] The gas supply system may be located between the blades and the support structure.

[0016] The ionization device may be located between the blades and the support structure.

[0017] The ionization device may be on the same side of the EUV radiation exposure zone as the gas supply system.

[0018] The ionization device may be located below the blades.

[0019] The ionization device may comprise a filament, an electron beam source or an RF system.

[0020] The lithographic patterning apparatus contamination control may further comprise one or more additional ionization devices.

[0021] According to a second aspect of the present invention, there is provided a lithographic apparatus comprising the lithographic patterning apparatus contamination control assembly of the first aspect.

[0022] According to a third aspect of the present invention, there is provided a method of controlling contamination of a lithographic patterning apparatus, the method comprising: providing a lithographic patterning apparatus not connected to ground; providing a shielding device connected to ground; directing EUV radiation onto the lithographic patterning apparatus at an exposure zone defined by the shielding device; and providing a quasi-neutral plasma to a region between the shielding device and the gas of the lithographic patterning apparatus.

[0023] The method may further comprise removing gas from the region between the shielding device and the lithographic patterning apparatus.

[0024] The shielding device may comprise at least one blade. The quasi-neutral plasma is located between the at least one blade and the patterning apparatus.

[0025] The shielding device may comprise a pair of blades. The quasi-neutral plasma may be located between each blade of the pair of blades and the patterning apparatus.

[0026] The quasi-neutral plasma may be located beside the exposure zone of the lithographic apparatus.

[0027] The quasi-neutral plasma may be at least partially generated by an ionization device located between the shielding device and the patterning apparatus.

[0028] The quasi-neutral plasma may be at least partially generated by an ionization device not located between the shielding device and the patterning apparatus, and wherein an air flow within the environment in which the patterning apparatus is provided moves the quasi-neutral plasma to between the shielding device and the patterning apparatus.

[0029] The quasi-neutral plasma may be generated by a plurality of ionization devices.

[0030] There may be a continuous flow of gas and quasi-neutral plasma through the environment in which the patterning apparatus is provided.

[0031] Features of different aspects of the present invention may be combined together. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention will now be described by way of example with reference to the accompanying schematic drawings, in which:

[0033] Figure 1 A lithographic system including a contamination control assembly according to an embodiment of the present invention is schematically depicted;

[0034] Figure 2 The contamination control assembly is schematically depicted in more detail; and

[0035] Figure 3 Schematically depicts the operation of parts of a pollution control assembly. Detailed implementation

[0036] Figure 1 Shows a lithography system including a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography apparatus LA. The lithography apparatus LA includes an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0037] The illumination system IL is configured to condition the EUV radiation beam B before the EUV radiation beam B is incident on the patterning device MA. Additionally, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and the faceted pupil mirror device 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. In addition to or instead of the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may include other mirrors or devices.

[0038] After being conditioned in this way, the EUV radiation beam B interacts with the patterning device MA. Due to 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. For this purpose, the projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B’ onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B’, thus forming an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is Figure 1 illustrated as having only two mirrors 13, 14, the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0039] The support structure MT may include a clamp for holding the patterning device MA. The clamp may be an electrically driven electrostatic clamp. There may be a dielectric layer between the clamp and the patterning device MA. The patterning device MA floats relative to electrical ground. At least a part of the support structure MT may be at electrical ground.

[0040] The patterning device MA and other components may be disposed within the housing 24. The interior defined by the housing may be referred to as the patterning device environment 25. The housing 24 may be substantially closed except for an opening at the bottom end of the housing. A masking device 20 including a pair of mask-blanking blades is disposed within the patterning device environment 25. The masking device 20 is used to selectively mask regions of the patterning device MA such that only a desired portion of the patterning device receives EUV radiation at any given time. During the scanning exposure, the patterning device MA and the support structure MT are moved in the y-direction, and the substrate W and the substrate table WT are moved in the opposite y-direction (and vice versa). In this way, the EUV radiation band passes over the patterning device MA and over the exposure field on the substrate W.

[0041] An ionization device 22 is disposed within the patterning device environment 25. Figure 1 The ionization device 22 in [the text] is located between the blades of the mask-blanking blade system 20 and the patterning device MA. However, the ionization device may be disposed at different locations within the patterning device environment 25. The ionization device is configured to initiate a quasi-neutral plasma in the region between the mask-blanking blade system 20 and the patterning device MA. This quasi-neutral plasma reduces the likelihood of contaminant particles impinging on the patterning device MA, as further explained below.

[0042] A relative vacuum may be provided in the radiation source SO, in the illumination system IL, and / or in the projection system PS, i.e., a small amount of gas (e.g., hydrogen gas) at a pressure substantially below atmospheric pressure. The same is the case for the patterning device environment 25. That is, there is a gas at a pressure below atmospheric pressure in the patterning device environment 25. For example, the gas may be hydrogen gas.

[0043] Figure 1 The radiation source SO shown in [the text] belongs to a type that may be referred to as a laser-produced plasma (LPP) source. A laser system 1 that may include a CO 2 laser is arranged to deposit energy via a laser beam 2 into a fuel (such as tin (Sn)) provided by a fuel emitter 3, for example. Although tin is mentioned in the following description, any suitable fuel may be used. The fuel may be in liquid form, for example, and may 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 towards the plasma formation region 4. The laser beam 2 is incident on the tin at the plasma formation region 4. The deposition of laser energy into the tin generates a tin plasma 7 at the plasma formation region 4. Radiation including EUV radiation is emitted from the plasma 7 during the de-excitation and recombination of electrons with the ions of the plasma.

[0044] The EUV radiation from the plasma is collected and focused by the collector 5. The collector 5 includes, for example, a near-normal incidence radiation collector 5 (sometimes more generally referred to as a normal incidence radiation collector). The collector 5 may have a multilayer mirror structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength such as 13.5 nm). The collector 5 may have an ellipsoidal configuration having two foci. The first of the foci may be at the plasma formation region 4, and the second of the foci may be at the intermediate focus 6, as discussed below.

[0045] The laser system 1 may be spatially separated from the radiation source SO. In such a case, the laser beam 2 may be transmitted from the laser system 1 to the radiation source SO by means of a beam delivery system (not shown) including, for example, suitable steering mirrors and / or beam expanders and / or other optical components. The laser system 1, the radiation source SO, and the beam delivery system may be considered together as a radiation system.

[0046] The radiation reflected by the collector 5 forms an EUV radiation beam B. The EUV radiation beam B is focused at the intermediate focus 6 to form an image at the intermediate focus 6 of the plasma present at the plasma formation region 4. The image at the intermediate focus 6 serves as a virtual radiation source for the illumination system IL. The radiation source SO is arranged such that the intermediate focus 6 is at or near the opening 8 in the enclosure structure 9 of the radiation source SO.

[0047] Although Figure 1 the radiation source SO is depicted as a laser-produced plasma (LPP) source, any suitable source such as a discharge-produced plasma (DPP) source or a free electron laser (FEL) may be used to generate EUV radiation.

[0048] Figure 2 Part of the lithographic apparatus LA is depicted schematically in more detail. Specifically, Figure 2 the patterning device MA, the support structure MT, the masking device 20, the ionization device 22, and other elements disposed in the housing 24 are depicted schematically. An opening 26 is provided at the lowermost end of the housing 24. The EUV radiation beam enters the housing 24 (and enters the patterning device environment 25) through this opening 26, is reflected from the patterning device MA, and then exits through the same opening 26. The masking device 20 defines an exposure zone strip 31 through which the EUV radiation passes.

[0049] The gas supply system 27 is provided in the housing 24. The gas supply system 27 includes one or more gas inlets configured to deliver gas to the patterning device environment 25. The gas may be provided at a pressure below atmospheric pressure. For example, the gas may be hydrogen. The gas supply system 27 may be located between the masking blades 32 of the masking device 20 and the patterning device MA.

[0050] The gas removal system 28 is provided in the housing 24. In the depicted embodiment, the gas removal system 28 is located on the side of the exposure zone 31 opposite the gas supply system 27 (although the gas removal system 28 may be provided at a different location). The gas removal system 28 includes one or more outlets configured to receive quasi-neutral plasma from the patterning device environment 25. The gas removal system 28 may also include a pump (not depicted) configured to pump the quasi-neutral plasma. The gas removal system 28 removes gas and quasi-neutral plasma from the patterning device environment 25. Additionally, the gas removal system 28 removes contaminants from the patterning device environment (as further explained below). The gas removal system 28 may be located between the masking blades 34 of the masking device 20 and the patterning device MA.

[0051] Figure 2 is a schematic diagram and is not intended to accurately depict the size or spatial configuration of the elements in the patterning device environment 25.

[0052] As depicted by the arrows, the gas supply system 27 and the gas removal system 28 provide an air flow across the patterning device environment 25. Specifically, there is an air flow through the space between the masking device 20 and the patterning device MA. The air flow may generally be in a single direction (e.g., the scan direction of the lithographic apparatus). However, the air flow may be more complex and may include flows in a number of different directions. There may be a continuous flow of gas and quasi-neutral plasma through the patterning device environment 31.

[0053] The gas may be delivered via one or more inlets (not depicted) at or adjacent to the opening 26. The air flow may be from the opening 26 towards the support structure MT. Such an air flow may advantageously reduce the likelihood of contaminant particles impinging on the reflectors 10, 11, 13, 14 of the lithographic apparatus (see Figure 1 ). The gas supply system 27 may be located outside the housing 24, for example in the opening 26 connected to the housing.

[0054] In the depicted embodiment, the ionization device 22 is located downstream of the gas supply system 27. The ionization device 22 can include, for example, a filament 29. A voltage is applied to the filament, and when gas flows over the filament, the voltage ionizes hydrogen gas to form a quasi-neutral plasma. The gas flow on the ionization device 22 (in this case, the filament 29) initiates a quasi-neutral plasma 30 between the patterning device MA and the blade 32 of the masking device 20.

[0055] In other embodiments, the ionization device need not be located downstream of the gas supply system. The gas within the patterning device environment 25 can move in various different directions and can come into contact with the ionization device due to this movement. Generally, it is desirable for the gas to reach the ionization device so that a quasi-neutral plasma can be generated.

[0056] In an embodiment, the filament 29 of the ionization device 22 is provided with sufficient energy to remove electrons from the gas flowing over it. For example, the ionization energy of a hydrogen atom is 13.6 eV, and the ionization energy of a hydrogen molecule is 15.4 eV. The filament 29 can be provided with a current of 0.1 A at a voltage of 5 V. Other currents and voltages can be used. The filament can be powered using a 0.1 to 5 W power supply. The electrons released by the filament 29 can have an energy greater than the ionization energy of the gas flowing over the filament. The ionization device 22 can include multiple filaments.

[0057] As depicted, the masking device 20 can include two blades 32, 34 that are separated from each other in the scanning direction of the lithographic apparatus. The scanning direction can be referred to as the Y direction. As schematically depicted, a first quasi-neutral plasma 30a can be formed between the first masking blade 32 and the patterning device MA, and a second quasi-neutral plasma 30b can be formed between the second masking blade 34 and the patterning device MA. The quasi-neutral plasmas 30a, 30b can be located beside the exposure zone 31 (as depicted).

[0058] In some embodiments, the quasi-neutral plasma can be provided only to one side (or mainly provided to one side) of the exposure zone 31.

[0059] Figure 3 Part of the patterning device MA and the support structure MT and part of the second blade 34 of the masking device 20 are schematically depicted. As schematically depicted, the quasi-neutral plasma 30b is located between the patterning device MA and the second blade 34. To the Figure 3 right, the voltage between the second blade 34 and the patterning device MA is schematically indicated by the dashed line in the schematic diagram 38.

[0060] As indicated, the masking device 20 including the second blade 34 is connected to ground. At least a portion of the support structure MT may be connected to ground. However, the patterning device MA is not connected to ground. Instead, the patterning device MA floats with respect to ground. When an EUV radiation beam B (see Figure 1 ) is incident on the patterning device MA during a lithographic exposure, it causes electrons to be emitted from the surface of the patterning device MA. As a result, the surface of the patterning device MA becomes positively charged. As schematically indicated by the double-headed arrow 40 in Figure 2 , the patterning device MA and the support structure MT move back and forth in the scanning direction (Y direction).

[0061] In Figure 3 , when the patterning device MA passes through the EUV radiation beam B (not depicted), its positively charged region then moves such that it is directly above the quasi-neutral plasma 30b (the movement is indicated by the arrow). In this example, the patterning device MA moves in the positive Y direction. However, in other examples, the patterning device MA moves in the negative Y direction and will be above the first quasi-neutral plasma 30a after passing through the EUV radiation beam.

[0062] Because the patterning device MA is positively charged, it attracts electrons from the quasi-neutral plasma 30b. As a result, the surface of the patterning device MA becomes negatively charged. This is schematically indicated by the voltage pattern 38 having a negative voltage at the surface of the patterning device MA.

[0063] Because the second blade 34 of the masking device 20 is connected to ground, the voltage at the second blade is zero. The quasi-neutral plasma has supplied some electrons to the surface of the patterning device MA and is thus slightly positively charged. This is represented as a slightly positive voltage on the pattern 38.

[0064] The quasi-neutral plasma typically includes equal amounts of electrons and positive ions. Thus, there is no significant electric field within the quasi-neutral plasma. This is schematically indicated by the voltage pattern 38, which shows no significant voltage change within the quasi-neutral plasma 30b (since the voltage is approximately constant, there is no significant electric field within the quasi-neutral plasma).

[0065] Charged contaminant particles within a quasi-neutral plasma do not experience a significant electric field. Accordingly, charged contaminant particles are not accelerated by an electric field towards the patterning device MA. If there were no quasi-neutral plasma 30b, the patterning device MA would become strongly positively charged due to the influence of the EUV radiation beam on the patterning device MA. Accordingly, there would be a substantial electric field between the patterning device MA and the second vane 34 of the shielding device 20. Such a substantial electric field would cause negatively charged contaminant particles to be accelerated towards the patterning device MA, such that the contaminant particles would likely impinge on the patterning device MA. This would cause defects in the pattern projected by the lithographic apparatus onto the substrate W. The quasi-neutral plasma avoids this problem, because it provides an environment in which charged contaminant particles are not accelerated towards the patterning device MA. Thus, contamination of the patterning device MA is reduced. This reduction in contamination of the patterning device MA is achieved without the need for a pellicle, and thus without a corresponding reduction in the EUV radiation intensity associated with the use of a pellicle.

[0066] As can be seen from Figure 3 the voltage profile 38 in, there is an electric field in the region immediately adjacent to the patterning device MA. Such a region may be referred to as a sheath region. As explained above, the surface of the patterning device MA is negatively charged. Accordingly, there is an electric field in the sheath region that repels negatively charged particles towards the quasi-neutral plasma. This is advantageous because the effect of the EUV radiation in the exposure zone 31 causes contaminant particles to be negatively charged. These negatively charged contaminant particles are deflected away from the patterning device MA by the electric field. The negatively charged contaminant particles enter the quasi-neutral plasma, where they no longer experience any electric force. The negatively charged contaminant particles are then removed from the patterning device environment 25, as explained below.

[0067] As described above in connection with Figure 2 the gas supply system 27 and the gas removal system 28 provide a gas flow (and a flow of the quasi-neutral plasma) across the patterning device environment 25. This gas flow removes charged contaminant particles from the patterning device environment 25. Charged contaminant particles within the quasi-neutral plasmas 30a, 30b are exhausted through the gas removal system 28. Charged particles in the sheath region between the quasi-neutral plasmas 30a, 30b and the patterning device MA can also be removed by the gas flow (the gas flow can deflect the charged particles such that they do not impinge on the patterning device MA).

[0068] A sheath region may also exist between the quasi-neutral plasmas 30a, 30b and the blades 32, 34 of the shielding device 20. In such a case, since the shielding device 20 is connected to ground, there is no acceleration of charged particles towards the shielding device. Similarly, the gas flow from the gas supply system 27 to the gas removal system 28 can carry charged contamination particles away from the patterning device environment 25, rather than incidenting the charged contamination particles on the blades 32, 34.

[0069] The quasi-neutral plasmas 30a, 30b are depicted in Figure 2 as generally being located above the inner ends of the first blade 32 and the second blade 34 of the shielding device 20. The quasi-neutral plasmas may be mainly located in these regions. However, the quasi-neutral plasmas may extend into other regions.

[0070] The patterning device environment 25 is dynamic in the sense that the patterning device MA moves in the positive and negative Y directions and thus experiences the charging effect of EUV radiation, while the gas supply system 27 delivers gas to the ionization device 22 and thus replenishes the quasi-neutral plasmas. The gas removal system 28 removes the quasi-neutral plasmas and contamination particles from the patterning device environment, while new gas is delivered by the gas supply system 27, thereby establishing a gas flow.

[0071] The gas flow can enable the ionization device 22 not to need to be located between the blade 32 of the shielding device 20 and the patterning device MA. Alternatively, the ionization device can be disposed at different locations in the patterning device environment 25, and nonetheless, can still provide quasi-neutral plasmas in the volume between the shielding device 20 and the patterning device MA.

[0072] In an embodiment, the ionization device 50 may be located below the first blade 32 of the shielding device 20, but still within the patterning device environment 25. In another embodiment, the ionization device 52 may be located below the second blade 34 of the shielding device 20, but still within the patterning device environment 25. In such a case, the ionization device 52 may be located above the beam attenuator 54, which is configured to move to intersect the EUV radiation beam partially to reduce the intensity of the EUV radiation beam when needed.

[0073] As further explained above, the ionization device may include a filament provided with a combination of current and voltage, which can separate electrons from the gas flowing through the filament.

[0074] In an embodiment, the ionization devices 22, 50, 52 may include an electron beam source. In such a case, the electrons provided from the electron beam source may have an energy greater than the ionization energy of the gas in the patterning device environment 25. For example, when the gas is hydrogen, the electrons may have an energy greater than 30.6 eV.

[0075] In an embodiment, the ionization devices 22, 50, 52 may be an RF system. The RF system may be configured to be modulated at a frequency of approximately 13.56 MHz. This frequency is known to be effectively absorbed by electrons, and this may cause electrons to be released from molecules to form a quasi-neutral plasma. The amplitude of the RF modulation may be, for example, a few volts (measured peak-to-peak). The RF system may include, for example, capacitively coupled plates or inductively coupled elements. The capacitively coupled plates may be circular or may have some other shape.

[0076] The ionization device may be an electron cyclotron resonance (ECR) plasma source.

[0077] More than one ionization device may be provided.

[0078] In this document, references to gas removal may be interpreted as covering the removal of quasi-neutral plasmas.

[0079] In this document, references to grounding may be interpreted as references to electrical grounding (which is alternatively referred to as earth grounding or simply grounding).

[0080] The method according to an embodiment of the present invention may be performed by a computing device. The device may include a central processing unit (“CPU”) connected to a memory. The methods described herein may be implemented as code (software) stored on a memory including one or more storage media and arranged, for example, to be executed on a processor including one or more processing units. The storage media may be integrated into the CPU and / or separate from the CPU. The code, which may be referred to as instructions, is configured to be retrieved from the memory and executed on the processor to perform operations in accordance with the embodiments discussed herein. Alternatively, it is not excluded that some or all of the functionality of the CPU is implemented in dedicated hardware circuitry or configurable hardware circuitry such as an FPGA.

[0081] The computing device may include an input configured to enable a user to input data into a software process running on the CPU. The input device may include a mouse, keyboard, touch screen, microphone, etc. The computing device may also include an output device configured to output the results of measurements to the user.

[0082] Although reference may be made specifically herein to the use of lithographic apparatus in the manufacture of integrated circuits, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, the guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0083] Although embodiments of the invention may be specifically referred to herein in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatuses. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing an object such as a wafer (or other substrate) or a mask (or other patterning device). These apparatuses may generally be referred to as lithographic tools. Such lithographic tools may operate under vacuum conditions or ambient (non-vacuum) conditions.

[0084] Although reference has been made specifically above to the use of embodiments of the invention in the context of optical lithography, it should be appreciated that, where the context allows, the invention is not limited to optical lithography and may be used in other applications, such as imprint lithography.

[0085] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); and the like. Additionally, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only and that such actions are in fact caused by computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc., and may cause actuators or other devices to interact with the physical world when such actions are performed.

[0086] Although specific embodiments of the invention have been described above, it should be understood that the invention may be practiced in other ways different from the described manner. The above description is intended to be illustrative, not restrictive. Thus, those skilled in the art will appreciate that the described invention may be modified without departing from the scope of the patent application set forth below.

Claims

1. A contamination control component for a lithographic pattern forming apparatus, comprising: a support structure configured to support a pattern forming apparatus, the pattern forming apparatus being floating relative to ground; a shielding device configured to selectively shield the lithographic pattern forming apparatus, the shielding device being connected to ground; a gas supply and an ionization device, the gas supply being configured to supply gas to the ionization device, and the ionization device being configured to convert the gas into a quasi-neutral plasma, the quasi-neutral plasma being located in a region between the shielding device and the lithographic pattern forming apparatus.

2. The contamination control component for a lithographic pattern forming apparatus according to claim 1, wherein, the component further includes a gas removal system configured to remove gas from a housing in which the support structure and the shielding device are located.

3. The contamination control component for a lithographic pattern forming apparatus according to claim 2, wherein, the gas removal system is located on a side of the EUV radiation exposure zone opposite to the gas supply system.

4. The contamination control component for a lithographic pattern forming apparatus according to any one of the preceding claims, wherein, the shielding device includes vanes.

5. The contamination control component for a lithographic pattern forming apparatus according to claim 4, wherein, the gas supply system is located between the vanes and the support structure.

6. The contamination control component for a lithographic pattern forming apparatus according to claim 4 or claim 5, wherein, the ionization device is located between the vanes and the support structure.

7. The contamination control component for a lithographic pattern forming apparatus according to claim 6, wherein, the ionization device and the gas supply system are located on the same side of the EUV radiation exposure zone.

8. The contamination control component for a lithographic pattern forming apparatus according to claim 4 or claim 5, wherein, the ionization device is located below the vanes.

9. The contamination control component for a lithographic pattern forming apparatus according to any one of the preceding claims, wherein, the ionization device includes a filament, an electron beam source or an RF system.

10. The contamination control component for a lithographic pattern forming apparatus according to any one of the preceding claims, further comprising one or more additional ionization devices.

11. A lithographic apparatus comprising the contamination control component for a lithographic pattern forming apparatus according to any one of the preceding claims.

12. A method of controlling contamination of a lithographic pattern forming apparatus, the method comprising: providing a lithographic pattern forming apparatus not connected to ground; providing a shielding device connected to ground; directing EUV radiation onto the lithographic pattern forming apparatus at an exposure zone defined by the shielding device; and providing a quasi-neutral plasma to a region between the shielding device and the gas of the lithographic pattern forming apparatus.

13. The method according to claim 12, wherein, the method further includes removing gas from the region between the shielding device and the lithographic pattern forming apparatus.

14. The method according to claim 12 or claim 13, wherein, The masking device includes at least one blade, and wherein, the quasi-neutral plasma is located between the at least one blade and the patterning device.

15. The method according to claim 14, wherein, the masking device includes a pair of blades, and wherein, the quasi-neutral plasma is located between each blade of the pair of blades and the patterning device.

16. The method according to any one of claims 12 to 15, wherein, the quasi-neutral plasma is located beside the exposure zone of the lithographic apparatus.

17. The method according to any one of claims 12 to 16, wherein, the quasi-neutral plasma is at least partially generated by an ionization device located between the masking device and the patterning device.

18. The method according to any one of claims 12 to 17, wherein, the quasi-neutral plasma is at least partially generated by an ionization device not located between the masking device and the patterning device, and wherein, an air flow in the environment in which the patterning device is disposed moves the quasi-neutral plasma to between the masking device and the patterning device.

19. The method according to claim 17 or claim 18, wherein, the quasi-neutral plasma is generated by a plurality of ionization devices.

20. The method according to any one of claims 12 to 19, wherein, there is a continuous flow of gas and quasi-neutral plasma through the environment in which the patterning device is disposed.

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