Pellicle Cleaning System

Abstract

A cleaning system for cleaning a component associated with a lithography process, such as a pellicle, reticle, wafer, or another lithography component, comprises at least one radiation emitter configured to irradiate an area of ​​the component, in use, to induce thermo-mechanical vibrations in the component and / or to induce sputtering of contaminants present on the component.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to European Patent Application No. 22153208.8, filed January 25, 2022, European Patent Application No. 22183953.3, filed July 8, 2022, and European Patent Application No. 22188666.6, filed August 4, 2002, each of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a cleaning system for cleaning a component associated with a lithographic process and to a method for using radiation to induce thermomechanical vibrations in the component and / or to induce sputtering of contamination present on the component. [Background technology]

[0003]

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can project a pattern from, for example, a patterning device (e.g. a mask, also known as a reticle) onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0004]

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

[0005]

[0005] The patterning device is typically protected by a pellicle. The pellicle comprises a thin membrane that is substantially transparent to lithographic radiation. The pellicle prevents particles (and other contaminants) from falling onto the patterning device or otherwise contaminating it. Over time, particles (which are prevented from contaminating the patterning device) accumulate on components of the lithographic apparatus, such as the pellicle and / or the substrate being patterned by the lithographic apparatus. Particle accumulation on the pellicle (for example) can cause defects in the pattern generated on the substrate.

[0006]

[0006] In some lithographic apparatus, multiple wafers of substrates are loaded onto a substrate table at one time and patterned by a single patterning device, and in such lithographic apparatus, a single defect at reticle level can cause a corresponding defect in the pattern generated on each wafer of substrate.

[0007] Contaminants may also build up on other components of the lithographic apparatus and cause defects in the patterns produced on the wafer by similar or other means.

[0008]

[0008] Before use in a lithographic apparatus, a pellicle can be tested for structural integrity. The test can include applying a relatively small difference in ambient pressure to each side of the membrane of the pellicle. The pressure can induce deformation of the pellicle. The deformation can be static, i.e., approximately constant during the time that the pressure is applied. If the structural integrity of the pellicle is less than the required level, the pellicle may be damaged. Inducing deformation in this way may not test the structural integrity of the pellicle in a similar manner across the entire surface of the pellicle. As a result, a pellicle that has passed the structural integrity test may be damaged during use of the lithographic apparatus, resulting in a period of time when the lithographic apparatus cannot be used as intended.

[0009]

[0009] One aim of the techniques described in this disclosure is to avoid or mitigate one or more of the problems discussed herein. Summary of the Invention

[0010] In examples described herein, a cleaning system for cleaning a component associated with a lithographic process comprises at least one radiation emitter configured, in use, to irradiate an area of ​​the component to induce thermo-mechanical vibrations in the component and / or to induce sputtering of contaminants present on the component. Advantageously, the cleaning system may be capable of cleaning the component.

[0011]

[0011] In another example described herein, a system for testing the structural integrity of a component associated with a lithography process comprises at least one radiation emitter configured to irradiate an area of ​​the component in use to induce thermo-mechanical vibrations in the component. Advantageously, testing the structural integrity of the component may indicate the ultimate tensile strength of the component. The testing may be destructive. Advantageously, the testing may avoid negative consequences of using a defective component.

[0012]

[0012] The component may be a component configured for use in a lithographic apparatus, a lithography tool, or a metrology tool. The component may be a substrate configured to be patterned by the lithographic apparatus, or a substrate already patterned by the lithographic apparatus. The component may also be a component for storing and / or transporting components related to a lithographic process, such as a reticle pod or a pellicle pod. The lithographic apparatus and / or the lithographic process may use DUV or EUV radiation. For example, the component may be a reticle, a pellicle, a reticle clamp, or a pellicle frame. The component may have a finite coefficient of thermal expansion.

[0013]

[0013] At least one radiation emitter may be a heater (i.e., the radiation emitter may emit heat or radiation that heats the component) and / or at least one radiation emitter may emit ions (i.e., the component may be irradiated with ions from the radiation emitter). Contaminants may not be completely removed from the component by sputtering. Sputtering may reduce the strength of the bonding forces (binding the contaminants to the component).

[0014]

[0014] The component may be a pellicle. Advantageously, the cleaning system enables cleaning of the pellicle so as to minimise defects on a wafer patterned by the lithographic apparatus.

[0015]

[0015] The system may further comprise a holder configured to hold the component. Advantageously, the holder may secure the component in a fixed position relative to the heater to ensure that the area of ​​the component that is heated by the heater is consistently the same area.

[0016]

[0016] The at least one radiation emitter may include a heater configured to irradiate an area of ​​the component, in use, to induce thermo-mechanical vibration in the component.

[0017]

[0017] The heater may be an electromagnetic radiation source. The heater may be a laser. Advantageously, this may allow for cleaning of the components using readily available and inexpensive equipment (e.g. without using EUV light). This may then maximize the availability of the lithography apparatus for patterning the wafer.

[0018]

[0018] The radiation provided by the heater may have a frequency between 300 GHz and 4300 THz. Advantageously, most of the light at such frequencies is absorbed by the component, thereby increasing the amplitude of the thermomechanical vibrations and improving the cleaning effect.

[0019]

[0019] The radiation provided by the heater may have an average power between 1 mW and 200 W. In cyclical heating, the average power may include contributions from when the component is not heated to when the component is heated. In other words, the power of the heater while it is applying heat may be higher than the average power.

[0020]

[0020] The radiation provided by the heater may be pulsed, in other words the heater may heat a region of the component in a cyclical manner, for example the heater may comprise a pulsed radiation source such as a pulsed laser.

[0021]

[0021] The radiation may have a pulse frequency between 1 Hz and 1 MHz.

[0022]

[0022] Each pulse of radiation may have a duration between 1 fs and 10 μs. Advantageously, such radiation characteristics may be optimal for inducing thermomechanical vibrations for cleaning the component.

[0023]

[0023] The holder may be positioned such that contaminants being cleaned from the component are removed from the vicinity of the component under the force of gravity, advantageously preventing the removed contaminants from re-contaminating the component (and / or other components) after removal.

[0024]

[0024] The heater may be configured to provide multiple beams of radiation, thereby allowing multiple areas of a single component to be heated simultaneously (and / or allowing multiple components to be heated) for more efficiently cleaning one or more components.

[0025] The heater may include multiple heaters to generate one or more of the multiple radiation beams.

[0026]

[0026] The heater may include one or more beam splitting and / or redirecting optics to generate one or more of the multiple radiation beams. For example, the holder may be configured to hold the component between the heater and the beam redirecting optics (e.g. mirrors) to allow heating of two sides of the component by a single radiation source.

[0027]

[0027] The holder may be one of a plurality of holders. The heater is configured, in use, to cyclically heat an area of ​​each of the plurality of components, each of the plurality of components may be held in one of the plurality of holders. This allows multiple components to be cleaned at once. This may be particularly advantageous in a batch cleaning process.

[0028]

[0028] The system may be configured such that, in use, different ones of the multiple radiation beams are incident on different ones of the multiple components.

[0029]

[0029] The heaters may be configured to heat different ones of the components at different wavelengths, allowing different types of components that absorb different wavelengths to be cleaned at once.

[0030]

[0030] At least one radiation emitter may include an ion source configured to direct ions to an area of ​​the component in use to induce sputtering of contaminants present on the component. Advantageously, the ions may cause a cleaning effect and / or enhance a cleaning effect provided by another radiation emitter (e.g. a heater). The ions may, for example, reduce the binding forces binding the contaminants to the component, thereby enabling the heater to remove contaminants (which would not otherwise be removed by the heater).

[0031]

[0031] The ions may be ions of a noble gas element, for example the ions may be argon cations, helium cations, and / or neon cations.

[0032]

[0032] The ion source may be configured to direct ions to a region of a first side of the component, in use, to induce sputtering of contaminants present on a second side of the component.

[0033]

[0033] The ion source may be configured to direct ions to a region of the first side of the component, in use, to induce sputtering of contaminants present on the first side of the component.

[0034]

[0034] At least one radiation emitter may include a heater configured to heat an area of ​​the component during use to induce thermo-mechanical vibration in the component, and an ion source configured to irradiate an area of ​​the component with ions during use to induce sputtering of contaminants present on the component.

[0035]

[0035] The system may further comprise a housing, the heater and holder being housed within the housing.

[0036] The enclosure may include a load lock chamber.

[0037]

[0037] The system may further comprise a vacuum pump. Alternatively, the system may comprise a nitrogen or hydrogen source to generate a nitrogen or hydrogen atmosphere within the enclosure.

[0038]

[0038] The system may further comprise a gas exhaust for removing contaminants.

[0039]

[0039] The system may further comprise metrology for measuring radiation emitted by the radiation emitter.

[0040]

[0040] The system may further comprise metrology for measuring contamination on or removed from the component. Such metrology may be used to provide feedback for, for example, dose control and to optimize cleaning time by avoiding unnecessary cleaning.

[0041]

[0041] The system may further comprise an adjuster for adjusting the slit width of the radiation between the first slit width and the second slit width. For example, the system may be used to clean a component and the system may be used to test the structural integrity of the component. The cleaning and testing may be performed in any order. Advantageously, the method may provide a defect-free component that has been screened for defects. For example, the system may be used to clean a component and the same system may be used to test the structural integrity of a second component. Advantageously, the method may clean and test a component. In other words, the system may be used for different purposes. Advantageously, the system may enable testing the structural integrity of a component before cleaning the same or another component. Advantageously, using the system in this way may allow defective components to be removed sooner, thus saving resources compared to cleaning all components before screening for defective components.

[0042]

[0042] In the examples described herein, a method of cleaning a component associated with a lithography process includes irradiating an area of ​​the component to induce thermo-mechanical vibrations in the component and / or to induce sputtering of contaminants present on the component.

[0043]

[0043] In another example described in this specification, a method for testing the structural integrity of a component associated with lithographic processing includes irradiating an area of ​​the component to induce thermo-mechanical vibrations in the component.

[0044]

[0044] Irradiating an area of ​​the component may include heating an area of ​​the component to induce thermo-mechanical vibration in the component.

[0045]

[0045] The heating may include providing one or more pulses of a pulse heater, in other words, the region of the component may be heated cyclically.

[0046]

[0046] Cyclic heating of the region of the component may be carried out for a period of time between 20 seconds and 1 hour, with 20 seconds being advantageously long enough to ensure that contaminants are removed from the component.

[0047]

[0047] The method may further comprise heating a second region of the component by a heater. Heating the component by radiation may further comprise periodically heating the second region of the component for between 20 seconds and 1 hour. Advantageously, heating the second region of the component ensures that all regions of the component are outside of the irradiated region (where cleaning effect is best) and therefore all regions can be properly cleaned.

[0048]

[0048] Irradiating the area of ​​the component may include directing ions to the area of ​​the component to induce sputtering of contaminants present on the component.

[0049]

[0049] Irradiating an area of ​​the component may include directing ions to an area of ​​a first side of the component to induce sputtering of contaminants present on a second side of the component.

[0050]

[0050] Irradiating an area of ​​the component may include directing ions to an area of ​​a first side of the component to induce sputtering of contaminants present on a second side of the component.

[0051]

[0051] Irradiating an area of ​​the component may include heating the area of ​​the component to induce thermomechanical vibration in the component, and irradiating the area of ​​the component with ions to induce sputtering of contaminants present on the component.

[0052]

[0052] The method may include irradiating a component with radiation having a first slit width and irradiating a second component with radiation having a second slit width. The component and the second component may be the same. Alternatively, the first and second components may be different.

[0053]

[0053] The method may include testing the structural integrity of the component by irradiating the component with radiation having a first slit width, narrowing a slit width of the radiation from the first slit width to a second slit width, and cleaning the component by irradiating the component with radiation having the second slit width.

[0054] In another example described herein, the controller is configured to control the system of the first example to perform the method of the second example.

[0055] In another example described herein, a component is cleaned according to the method of the second example. Advantageously, the component cleaned according to the method disclosed herein may be a cleaner. In the example where the component is a pellicle, the membrane of the pellicle cleaned according to the method disclosed herein may have a higher tension than otherwise. [Brief description of the drawings]

[0056]

[0056] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings.

[0057] [Figure 1] 1 depicts a lithography system comprising a lithographic apparatus and a radiation source. [Diagram 2] 1 illustrates an exemplary cleaning tool for cleaning components associated with a lithography process. [Figure 3A] 1 illustrates an alternative exemplary configuration of a cleaning tool for cleaning components associated with a lithography process. [Figure 3B] 1 illustrates an alternative exemplary configuration of a cleaning tool for cleaning components associated with a lithography process. [Figure 3C] 1 illustrates an alternative exemplary configuration of a cleaning tool for cleaning components associated with a lithography process. [Figure 4] Shown is a pellicle. [Diagram 5] 1 is a graph illustrating the cleaning performance of a cleaning tool for cleaning components associated with a lithography process. [Figure 6A] 13 is a graph illustrating cleaning performance of a cleaning tool within an illuminated area of ​​a component. [Figure 6A] 13 is a graph illustrating the cleaning performance of a cleaning tool outside the illuminated area of ​​a component. [Figure 7] 1 illustrates another exemplary cleaning tool. [Figure 8] 8 illustrates another exemplary component of the cleaning tool of FIG. 7. [Figure 9A] 1 shows a first schematic diagram of components related to a lithographic process being cleaned; [Figure 9B] FIG. 2 shows a second schematic diagram of components associated with the lithography process being cleaned. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] 1 shows a lithography system comprising a radiation source SO and a lithographic apparatus LA. The source SO is configured to generate a beam of EUV radiation B and to provide this beam of EUV radiation 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, also called a reticle), a projection system PS, and a substrate table WT configured to support a substrate W.

[0059]

[0058] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. To that end, the illumination system IL may comprise a facetted field mirror device 10 and a facetted pupil mirror device 11. Together the facetted field mirror device 10 and the facetted pupil mirror device 11 impart a desired cross-sectional shape and a desired intensity distribution to the EUV radiation beam B. The illumination system IL may comprise other mirrors or devices in addition to or instead of the facetted field mirror device 10 and the facetted pupil mirror device 11.

[0060]

[0059] After being so conditioned, the EUV radiation beam B interacts with the patterning device MA. This interaction results in a patterned EUV radiation beam B'. 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 comprise a number of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by a substrate table WT. The projection system PS may apply a demagnification factor to the patterned EUV radiation beam B', thereby forming images of features that are smaller than corresponding features on the patterning device MA. For example, a demagnification factor of 4 or 8 may be applied. Although the projection system PS is shown in Figure 1 as having only two mirrors 13, 14, the projection system PS may comprise a different number of mirrors, for example 6 or 8 mirrors.

[0061]

[0060] The substrate W may include a preformed pattern. In such a case, the lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the preformed pattern on the substrate W.

[0062] A relative vacuum, ie a small amount of gas (eg hydrogen) at a pressure significantly below atmospheric pressure, may be provided in the source SO, illumination system IL and / or projection system PS.

[0063]

[0062] The source SO may be a laser-produced plasma (LPP) source, a discharge-produced plasma (DPP) source, a free-electron laser (FEL) or any other source capable of producing EUV radiation.

[0064]

[0063] Contaminants (e.g. particles or vapour present in the lithographic apparatus LA) can accumulate on the surface of the patterning device MA. Contaminant accumulation on the patterning device MA can lead to defects in the pattern of the patterning device MA, causing defects in the pattern of the patterned EUV radiation beam B' and consequently in the pattern generated on the substrate W. Multiple substrates W may be loaded at one time on the substrate table WT and exposed sequentially. Hence, a single defect in the patterning device MA (e.g. due to a build-up of contaminants) can lead to multiple defects in the pattern generated on the substrate W.

[0065]

[0064] To mitigate the build-up of contaminants on the patterning device MA, the lithographic apparatus LS may comprise a pellicle 15. The pellicle 15 is positioned adjacent to or at a short distance from the patterning device MA to allow contaminants that would otherwise contaminate the patterning device MA (and cause defects in the pattern formed by the patterned EUV radiation beam B') to build up on a surface of the pellicle 15. For example, in the exemplary lithographic apparatus LA, the pellicle 15 is positioned on a downward-facing side of the patterning device MA, i.e., the side opposite the support structure MT. The pellicle 15 may prevent contaminants from building up on the patterning device MA and thus mitigate the defects associated therewith.

[0066]

[0065] The pellicle 15 may include a membrane and a boundary. The membrane, alternatively referred to as a film, may be substantially transparent to EUV radiation. That is, the EUV radiation beams B, B' may pass through the pellicle 15 while a relatively small amount of energy from the EUV radiation beams B, B' is absorbed by the pellicle 15. By way of example only, the pellicle 15 may include silicone (Si) or carbon nanotubes. The pellicle 15 may be open (i.e., the membrane is a mesh and is permeable to gas) or closed (i.e., the membrane provides a continuous surface between each edge of the boundary and is impermeable to gas). The pellicle 15 may further include one or more layers of a metal having a high emissivity, such as a metal layer. A pellicle 15 including a metal layer may maintain a lower temperature (during use in the lithography system LA) than another. The membrane may be secured to the boundary during the manufacturing steps such that the surface of the membrane is kept in tension. Alternatively, the membrane and boundary may include a single homogenous material. The pellicle 15 may be constructed in different ways or from different materials, for example depending on or optimized for the wavelength of the radiation beam B, B' with which the pellicle 15 is expected to be used.

[0067]

[0066] The pellicle 15 may be removably mounted to the patterning device MA or to the support structure MT. In the exemplary lithographic apparatus LA, the pellicle 15 is removably mounted to the patterning device MA by using a pellicle frame 16. Removably mounting the pellicle 15 allows it to be removed and / or replaced as required.

[0068]

[0067] When the pellicle 15 is fixed in position, the EUV radiation beam B passes through the pellicle 15 before being patterned (by the patterning device MA), and the patterned EUV radiation beam B' passes through the pellicle after being patterned (by the patterning device MA).

[0069]

[0068] Over time, particles may accumulate on the surface of the pellicle 15, typically on the surface opposite the patterning device MA. Because the pellicle 15 is adjacent to the patterning device MA or at a short distance therefrom (i.e. outside the field plane of the lithographic apparatus LA), contaminants accumulating on the pellicle 15 may be out of focus of the EUV radiation beam B, B'. This accumulation of contaminants on the pellicle 15 may therefore reduce defects in the patterned EUV radiation beam B' (compared to defects caused by a similar level of contaminants accumulated on the patterning device MA). This may lead to a reduction in defects (in number and / or size) in the pattern generated on the substrate W.

[0070]

[0069] Furthermore, with extended use, contaminants may further accumulate on the surface of the pellicle 15, causing unacceptable defects in the patterned EUV radiation beam B' and the pattern produced on the substrate W. Also, the pellicle may become contaminated during manufacturing, necessitating cleaning prior to the initial use of the pellicle.

[0071] Additionally or alternatively, contaminants may build up on surfaces of other components of the lithographic apparatus LA. For example, contaminants may build up on the surface of the substrate W before and / or after it is patterned by the radiation beam B'. If the substrate W is contaminated (with contaminants) before it is patterned, areas on the surface of the substrate W may be obscured by contaminants and may not be properly exposed to the patterned EUV radiation beam B'.

[0072]

[0071] As another example, contaminants may accumulate on the surface of the patterning device MA (i.e. the reticle). Such accumulation may occur regardless of whether the lithographic apparatus LA is equipped with a pellicle 15. For example, contaminants may accumulate before the patterning device MA is loaded into the lithographic apparatus (LA), before the pellicle 15 is loaded into the lithographic apparatus LA, and / or after both the patterning device MA and the pellicle 15 are loaded into the lithographic apparatus LA. Contaminants accumulated on the surface of the patterning device may cause defects in the pattern generated on the substrate W, similar to the above.

[0073] As another example, contaminants may accumulate on the surfaces of pellicle frame 16. Pellicle frame 16 may transfer the contaminants onto pellicle 15 (or onto another pellicle after pellicle 15 is replaced), which may cause defects similar to those described above.

[0074]

[0073] As another example, contaminants may accumulate on surfaces of devices configured to manipulate, store, and / or transport reticles and / or pellicles. Such devices may be referred to as reticle pods. A contaminated reticle pod may contaminate pellicles that are manipulated, stored, or transported by the reticle pod, thereby causing defects similar to those described above.

[0075]

[0074] A lithography tool is a tool configured to pattern a substrate using radiation. A metrology tool is a tool configured to measure features of a lithography apparatus or a substrate patterned by a lithography apparatus. In other words, a lithography tool or a metrology tool may be described as a tool associated with a lithography process. As another example of harmful contaminant buildup, a lithography tool and / or a metrology tool may become contaminated. The contaminants may cause defects in the performance of the (lithography or metrology) tool and / or contaminate the lithography apparatus or substrates used with the tool.

[0076]

[0075] In other words, contaminants may accumulate on surfaces of components related to the lithographic process. The components related to the lithographic process may include components of the lithographic apparatus LA, lithography tool, metrology tool, and / or reticle pod. The components related to the lithographic process may include a substrate configured to be patterned by the lithographic apparatus, or a substrate already patterned by the lithographic apparatus. Exemplary components include a reticle, a pellicle, a reticle clamp, and a pellicle frame. Although the lithographic apparatus LA described so far is described as using EUV radiation, the lithographic apparatus LA or the lithographic process may use DUV radiation.

[0077] In one example, a cleaning tool for cleaning a component associated with a lithography process includes a heater. During use to clean the component, the heater provides radiation that heats an area of ​​the component to induce thermomechanical vibration in the component. The thermomechanical vibration of the component dislodges / liberates contaminants from a surface of the component, thereby generating a cleaning effect.

[0078]

[0077] The heater may be a radiation source. The radiation (heating an area of ​​the component) may be periodic. The heater may take any suitable form and be referred to as a component heater. For example, the heater may be a laser and the radiation may be laser light. As an alternative example, the heater may be a lithography device and the laser light or generated lithography radiation (e.g. EUV radiation B, B', or DUV radiation in a DUV lithography system) heats the component. As used herein, the term radiation refers to electromagnetic radiation.

[0079]

[0078] The component (i.e. a component related to the lithographic process cleaned by the cleaning tool) may be a component of the lithographic apparatus LA, a lithography tool, or a metrology tool. The component may be a substrate configured to be patterned by the lithographic apparatus, or a substrate already patterned by the lithographic apparatus. Exemplary components of the lithographic apparatus LA that may be cleaned by the apparatus cleaning tool include a reticle (such as the fabrication device MA), a reticle clamp, a pellicle (such as the pellicle 15), or a pellicle frame. According to an exemplary method of cleaning operation (discussed below), any component that is sufficiently absorbing of radiation and has a finite coefficient of thermal expansion may be cleaned.

[0080] 2 illustrates an exemplary cleaning tool 200 that includes a heater 220. The cleaning tool 200 further includes a mount 210. The heater 220 may be a laser. A component 201 is removably mounted to the mount 210. The component 201 is heated by radiation 230 provided by the heater 220. The cleaning tool 200 may alternatively be referred to as a cleaning system.

[0081]

[0080] In the exemplary cleaning tool 200, the mount 210 includes clamps 212, 214. Although the cleaning tool 200 is illustrated as including the mount 210, the mount 210 is not an essential feature of the cleaning tool 200. The mount 210 can advantageously hold the component 201 in a fixed position relative to the heater 220 so that an area of ​​the component 201 is consistently heated by the heater 220. In other words, the mount 210 prevents relative movement of the component 201 with respect to the heater 220, which causes the heater 220 to heat the intended area of ​​the component 201. The mount 210 may not be necessary in cleaning tools configured to clean larger components or fixed components. Additionally or alternatively, other fastening means may be provided. For example, the component 201 may be fastened to the heater 220 using other means. As an example, the cleaning tool 200 may include a clamp that secures the cleaning tool 200 (and heater 220) to the component 201 or to another structure fixed relative to the component 201. For example, the cleaning tool 200 may be secured to the lithographic apparatus LA to enable the cleaning tool 200 to clean a component of the lithographic apparatus LA. Additionally or alternatively, the mount 210 may be configured to allow the component 201 to be stably placed on the mount 210. For example, the mount 210 may be configured such that the component 201 can be placed on the mount 210 and held in place by gravity.

[0082]

[0081] As discussed above, the component 201 cleaned by the cleaning tool may be any component associated with a lithography process. In FIG. 2 and the corresponding description, the component 201 is a pellicle. However, it will be understood that the pellicle 201 is one example of a component associated with a lithography process, and the cleaning tool 200 is not limited to only cleaning pellicles. Similarly, in FIG. 2 and the corresponding description, the radiation 230 is pulsed (i.e., provides periodic heating). It will be understood that the periodic aspect of the radiation 230 is an exemplary and not a required feature.

[0083]

[0082] Pellicle 201 may be similar or identical to pellicle 15. Pellicle 201 may have been previously contaminated with contaminants (e.g., particles and / or vapors) and require cleaning. In the following text, cleaning tool 200, heater 220, and mount 210 may be referred to as pellicle cleaning tool 200, pellicle heater 220, and pellicle mount 210, respectively.

[0084]

[0083] During operation, the radiation 230 provides thermal energy to a region of the pellicle 201. By pulsing the radiation 230 irradiating the pellicle 201 (i.e., by repeatedly irradiating and not irradiating the pellicle 201), the pellicle 201 heats and cools rapidly, inducing thermomechanical vibrations in the pellicle 201 due to its finite thermal expansion rate. The thermomechanical vibrations provide sufficient energy and momentum to release particles (and possibly other contaminants) from the surface of the pellicle 201. The energy and momentum to release the particles can alternatively be viewed as an acceleration of and force applied to the pellicle 201 and contaminants. For some types of pellicles 201, prolonged exposure to one or more pulses of radiation 230 can damage the pellicle 201, for example due to deformation, oxidation, and / or mechanical fatigue. The deformation of the pellicle 201 can alternatively be referred to as wrinkling. In some examples, the characteristics of the radiation 230 (e.g., the duration that the (pulsed) radiation 230 irradiates the pellicle 201) can be limited to ensure that the pellicle 201 is not damaged. Damage to the pellicle 201 may be repairable or reversible.

[0085]

[0084] As mentioned above, the pellicle heater 220 may be a laser. The laser may include a pump source, a gain medium, and one or more mirrors (not shown). The laser may be a narrowband laser. When a wavelength (of the radiation 230 provided by the pellicle heater 220) is mentioned herein, this may refer to a single wavelength in instances where the pellicle heater 220 is a narrowband laser.

[0086]

[0085] The pellicle heater 220 may include a pellicle heater housing 222 and / or may be powered by a power supply 224.

[0087]

[0086] The pellicle heater 220 can be pulsed or have other mechanisms for rapidly changing the cycle of radiation 230. In an example where the pellicle heater 220 is a laser, the laser may be a pulsed laser. Experimental results (discussed further below) indicate that a pulse rate of about 1 Hz to 1 MHz and an irradiation period of about 1 fs to 10 μs may be appropriate. For some types of pellicles 201, a pulse rate of 10 kHz and / or an irradiation period of 10,000 ns may be suitable.

[0088]

[0087] The characteristics of the radiation 230 can be adapted to the characteristics of the pellicle 201. For example, the radiation 230 can be adapted in space to an eigenmode of the membrane of the pellicle 201 and in time to an eigenfrequency corresponding to this eigenmode. In other words, the radiation 230 can be adapted to advantageously utilize the resonant frequencies of the normal modes of the pellicle 201 for improved cleaning.

[0089]

[0088] The characteristics of the radiation 230 (e.g., power, wavelength, and / or frequency) may be selected to ensure that the pellicle 201 being cleaned absorbs enough energy to induce thermomechanical vibrations of the pellicle 201 that produce the cleaning effect, but does not absorb so much energy that it damages the pellicle 201. For example, the characteristics of the radiation 230 may be selected to ensure that the pellicle 201 heats up less than 1000K per pulse of radiation. As an example, some pellicles are known to absorb most of the energy provided in the IR spectrum (300 GHz to 4300 THz). Thus, for such pellicles, it may be preferable for the radiation 230 to have a wavelength corresponding to the IR spectrum to maximize absorption of the radiation 230 by the pellicle. Alternatively, wavelengths corresponding to the visible spectrum (400 THz to 790 THz) or UV spectrum (750 THz to 30 PHz) may be beneficial for irradiating pellicles 201 constructed using other means. More generally, any wavelength of radiation 230 may be used, provided that the radiation is sufficiently absorbed by the component 201 to produce a cleaning effect, for example wavelengths up to 1 mm.

[0090] Additionally or alternatively, the properties of the radiation 230 may be selected to increase or optimize the acceleration of the thermomechanical vibrations induced in the pellicle 201. In other words, the induced thermomechanical vibrations are characterized by one or more mechanical waves propagating through the pellicle 201, and the properties of the radiation 230 may be selected to increase or optimize the acceleration (i.e., the amplitude of the acceleration) of the one or more mechanical waves. Advantageously, the increased acceleration may improve the cleaning effect. For example, decreasing the slit width (in one or more dimensions) of the radiation 230 may shorten the wavelength of the one or more mechanical waves. Assuming a constant speed of the one or more mechanical waves in the component 201, a shorter wavelength may increase the frequency and therefore the acceleration of the one or more mechanical waves. Such an increased acceleration may reduce the intra-pulse intensity and / or reduce the time-averaged intensity of the radiation 230.

[0091]

[0090] Increasing the power of the radiation 230 (e.g. 200 W) can provide more energy to, for example, a pellicle 201 that is poorly absorbing at the wavelength of the radiation 230 being used. As a counter example, for a pellicle 201 that absorbs most of the energy from the radiation 230, a lower power of radiation 230 may be sufficient. For example, for a pellicle 201 that absorbs most of the radiation 230 from the IR spectrum, irradiating the pellicle 201 with IR radiation 230 of 1 mW power may be sufficient.

[0092]

[0091] Similarly, the power of radiation 230 may depend on the pulse rate and pulse length. For example, at a low pulse rate and / or a short pulse length, radiation 230 irradiates pellicle 201 for a shorter time than otherwise. Thus, radiation 230 may require more power when a low pulse rate and / or a short pulse length is used (and vice versa). A low pulse rate and / or a short pulse length may generate higher frequency thermomechanical vibrations (than otherwise), thereby achieving improved cleaning effects (than otherwise). Alternatively, radiation may be continuous (i.e., from a continuous laser) or single pulse (i.e., a single pulse of a pulsed laser). In other words, radiation 230 may heat an area of ​​pellicle 201 only once.

[0093]

[0092] The radiation 230 may not have a single consistent pulse rate and / or pulse length. For example, the pulse rate may be at a first value but change (gradually or instantaneously) to a second value. Alternative pulse patterns may be used.

[0094]

[0093] The radiation 230 may be a beam and may have a shape or profile. For example, the area of ​​the pellicle 201 illuminated by the radiation 230 may have a circular, square, rectangular, crescent, or other similar shape. The power and / or shape of the beam of radiation 230 may be selected to correspond to the bulk wave propagation velocity of the material of the pellicle 201 to provide optimal cleaning results. As an example, the radiation 230 may have a circular profile with a radius of less than 1 mm. As an alternative, the radiation 230 may have a narrow rectangular (i.e. "slit") profile with dimensions less than 1 mm. Such a slit may be optimal for some materials. As an alternative, for other shapes, a beam with a meniscus (i.e. crescent) profile may be optimal.

[0095]

[0094] The radiation 230 may be incident on the pellicle 201 at any angle. To minimize reflection of the radiation 230 from the pellicle 201 (and thus achieve greater absorption), an angle of incidence of about 0 degrees (i.e., the angle between the radiation 230 and a line extending perpendicularly from the surface of the pellicle 201) may be used. Alternatively, the angle of incidence may be selected to obtain a desired absorption of the radiation, or taking into account other considerations, such as the layout of the pellicle cleaning tool 200.

[0096] Experimental results show that areas of the pellicle 201 outside the irradiated area (i.e., the area irradiated with radiation 230) can be significantly cleaned than the irradiated area. In other words, more contaminants can be removed from the pellicle 201 when an area other than the area containing the contaminants is irradiated than when the area containing the contaminants is irradiated. Thus, the tool 200 can include a means for adjusting the area irradiated (by radiation 230) on the pellicle 201. For example, the pellicle heater 220 can include an actuator to irradiate different areas of the pellicle 201 by changing the position or angle of the pellicle heater 220. Additionally or alternatively, the pellicle mount 210 (or any additional or alternative fastening means) can include an actuator to change the area of ​​the pellicle 201 that is irradiated by changing the position of the pellicle 201 (e.g., by raising or lowering the clamps 212, 214). Additionally or alternatively, one or more beam positioning devices (mirrors, lenses, etc.) may be provided between the pellicle heater 220 and the mount 210 to direct the radiation 230 .

[0097]

[0096] The radiation 230 may not be fully absorbed by the pellicle 201. The pellicle cleaning tool 200 may include means for safe dispersion or absorption of the radiation 230, such as a beam dump (not shown). The beam dump may be provided in a position such that the radiation 230 is incident on the beam dump after irradiating the pellicle 201.

[0098]

[0097] One or more optical components, such as, for example, a mirror, may be used to redirect the radiation 230 before or after irradiating the pellicle 201. For example, a mirror can direct the radiation 230 after irradiating the pellicle 201 to a beam dump.

[0099]

[0098] The pellicle cleaning tool 200 may include metrology for measuring the intensity of the radiation 230 before or after irradiation of the pellicle 201. For example, the pellicle cleaning tool 200 may calculate the dose of radiation 230 received by the pellicle 201 by measuring the intensity of the radiation 230 before and after irradiation of the pellicle 201. The intensity of the radiation 230 before irradiation of the pellicle 201 may be estimated based on known or measured characteristics of the pellicle heater 220. Metrology for measuring the intensity of the radiation 230 after irradiation of the pellicle 201 may be provided in or along with the beam dump.

[0100]

[0099] The pellicle mount 210 may include attachments to allow the pellicle 201 to be removably fixed in a position illuminated by the pellicle heater 220. For example, the pellicle mount 210 may include one or more clamps 212, 214. One or more clamps 212, 214 may be provided in fixed positions on opposite sides of the pellicle 201, for example on the upper and lower sides of the pellicle 201. Advantageously, the tolerances for the position of the pellicle 201 in the pellicle cleaning tool 201 are looser than the tolerances for the position of the pellicle 15 in the lithographic apparatus LA. Alternatively, the pellicle mount 210 may use substantially the same hardware and fixing methods as those provided for the pellicle frame 16, for example, as known to those skilled in the art.

[0101] [000100] Pellicle 201 can be removably secured to pellicle mount 210 such that one side of pellicle 201 is irradiated with radiation 230. The side of pellicle 201 irradiated with radiation 230 can be either side of the membrane (or the side of a metal coating on the membrane). The side of the membrane irradiated by pellicle heater 230 can be the side (of pellicle 201) on which contaminants have accumulated, or the side opposite the side on which contaminants have accumulated.

[0102] [000101] The pellicle cleaning tool 200 may include a housing 226 in which the pellicle mount 210 and the pellicle heater 220 are provided. The housing 226 may provide a sealed environment for the pellicle cleaning tool 200. The housing 226 is shown with dashed lines to indicate that a housing may not be present in all illustrative embodiments; that is, the tool 200 may be contained within another system and may not include a dedicated housing.

[0103] [000102] The pellicle cleaning tool 200 may include components for providing a low ambient pressure within the housing 226, such as a vacuum pump (not shown). A low ambient pressure, such as an ultra-high vacuum (UHC), may advantageously contribute to the removal of contaminants from the pellicle 201 and may also contribute to the removal of contaminants from areas near the pellicle 201 (after the contaminants have been removed from the pellicle 201). Alternatively or additionally, the pellicle cleaning tool 200 may include components (not shown) for providing an internal environment (i.e., the interior of the housing) enriched with a particular gas, such as nitrogen or hydrogen. An internal environment enriched with nitrogen may help prevent damage to the pellicle 201 (e.g., due to oxidation) and / or increase the rate at which the pellicle 201 cools after heating by radiation 230 (which may increase the amplitude of the thermo-mechanical vibrations generated).

[0104] [000103] The housing 226 can include a hatch (not shown) or otherwise that is opened to provide access to the pellicle cleaning tool 200, for example to allow for the loading (or removal) of the pellicle 201 onto (or from) the pellicle mount 210. Alternatively or additionally, the housing 226 can include a panel that can be removably secured to the housing to provide access. The hatch (or panel), when closed, can provide an air-tight (i.e., vacuum-resistant) seal within the housing 226.

[0105] [000104] The enclosure 226 may include a chamber (i.e., a load lock chamber) with two hatches, allowing the pellicle 201 to be inserted or removed from the enclosure without compromising the enclosure's internal environment. The chamber may define (and seal) an internal environment separate from the enclosure's 226 internal and external environments. The first hatch (of the two hatches) may open to the external air, and the second hatch may open to the enclosure's internal air. The load lock may prevent both hatches from being opened at the same time. To load the pellicle 201, the first hatch may be opened and the pellicle 201 may be placed in the chamber. The first hatch may be closed and the chamber's internal environment may be equalized (or nearly equalized) with the enclosure's 226 internal environment. For example, the ambient pressure may be reduced to near the pressure in the enclosure 226 and / or the nitrogen concentration may be increased to near the nitrogen concentration in the enclosure's 226 internal environment. After equalization, the second hatch can be opened and the pellicle 201 can be moved from the chamber to the pellicle mount 210. To remove the pellicle 201 from the housing 226, the process can be reversed.

[0106] [000105] The enclosure 226 may include a system for removing the contaminants from the internal environment once they are released from the pellicle 201. For example, a gas inlet may direct the contaminants towards an exhaust for removal from the internal environment of the enclosure 226.

[0107] [000106] The housing 226 can include components to aid in the insertion or removal (from the housing or load lock chamber) or mounting or dismounting (with respect to the pellicle mount 210). For example, the housing 226 can include a robotic arm (not shown). Alternatively or additionally, the pellicle mount 210 itself can be movable and moved from a position within the housing to a position within the load lock chamber. For example, the pellicle mount 210 can be provided on rails or a control system to move the pellicle mount 210 along the rails from a first position within the housing 206 (where the pellicle 201 can be irradiated with radiation 230) to a second position within the load lock chamber (where the pellicle 201 can be removed from the pellicle mount 210 when a first hatch of the load lock chamber is open).

[0108] [000107] The pellicle cleaning tool 200 may include a component for measuring contamination of the pellicle 201. This component may be, for example, a camera or metrology including a laser (in an example where the pellicle heater 220 is a laser, i.e., a pellicle heating laser or an additional laser). The component for measuring contamination of the pellicle 201 may measure the contamination one or more times. For example, the contamination of the pellicle 201 may be measured once before cleaning to indicate whether cleaning is necessary or how long the cleaning should continue (i.e., how long the radiation 230 should irradiate the pellicle 201). Additionally or alternatively, the contamination of the pellicle 201 may be measured continuously (or at regular intervals) to provide an indication of whether cleaning of the pellicle 201 should continue. The measurement of the contamination of the pellicle 201 may be a measurement of the contamination in various areas of the pellicle 201 and may provide an indication of where the radiation 230 should irradiate the pellicle 201.

[0109] [000108] To enable in-situ cleaning, the lithographic apparatus LA may include a pellicle cleaning tool 200. Other tools or components used in lithography, such as metrology tools, may also include a pellicle cleaning tool 200.

[0110] [000109] Pellicle cleaning tool 200 may be used during manufacture of pellicle 201, for example before or after fixation of the membrane to the interface. Radiation 230 may irradiate the membrane of pellicle 201. In addition to cleaning the pellicle, tool 200 may advantageously increase the surface tension of the membrane.

[0111] [000110] Figures 3A-3D show examples of pellicle cleaning tools 300a, 300b, 300c, and 300d, respectively, each of which includes substantially the same components as pellicle cleaning tool 200 (i.e., radiation 330 is provided by a pellicle heater 320, and a pellicle 301 is removably secured to a pellicle mount 310 and irradiated with radiation 330). In the figures described herein, like or corresponding elements are given like or corresponding reference numbers.

[0112] [000111] Figure 3A shows a pellicle cleaning tool 300a including a pellicle 301. The pellicle 301 is held in a pellicle mount 310 and aligned in a substantially horizontal position. Radiation 330 is applied from a pellicle heater 320 located vertically above the pellicle 301 (with respect to gravity) to heat the pellicle 301. The pellicle 301 may be positioned such that the side of the pellicle 301 that is more highly contaminated or expected to be more highly contaminated (i.e. the side of the pellicle 301 that will face away from the patterning device MA when placed in position within the lithographic apparatus LA) faces downwards (i.e. away from the incident radiation 330). Advantageously, gravity can aid in the release of contaminants from the pellicle 301 and / or the removal of released contaminants from areas proximate to the pellicle 301.

[0113] [000112] Figure 3B illustrates a pellicle cleaning tool 300b having substantially the same components as pellicle cleaning tool 200, and further including one or more mirrors 341, 342. A portion of the radiation 330 irradiating the pellicle 301 is not absorbed by the pellicle 301, and after passing through the pellicle 301, attenuated radiation 332 propagates away from the pellicle 301. The one or more mirrors 341, 342 reflect and redirect the attenuated radiation 332 back towards the pellicle 301. The attenuated radiation 332 may irradiate the pellicle 301 on a side of the pellicle 301 opposite the side irradiated by radiation 330. The attenuated radiation 332 may irradiate the pellicle 301 in an area opposite the area irradiated by radiation 330. Alternatively, the attenuated radiation 332 may irradiate the pellicle 301 in an area different from the area opposite the area irradiated by radiation 330. Advantageously, one or more mirrors 341, 342 allow the pellicle 301 to be irradiated multiple times (in a single area or in multiple areas) by a single pellicle heater 320. This can therefore increase the energy absorbed by the pellicle 301 and increase the frequency or amplitude of the induced thermo-mechanical vibrations.

[0114] [000113] Figure 3C shows a pellicle cleaning tool 300c that includes two pellicle heaters 320a, 320b. The pellicle heaters 320a, 320b provide radiation 330a, 330b that irradiates the pellicle 301. The radiation 330a, 330b irradiates the pellicle 301 at two points or at a single point. Although the radiation 330a, 330b is provided by the pellicle heaters 320a, 320b (in the example of the pellicle cleaning tool 300c), it will be appreciated that more than one beam of radiation 330a, 330b may be provided by using beam splitting optics and a single pellicle heater.

[0115] [000114] Figure 3D shows a pellicle cleaning tool 300d including a pellicle heater 320, multiple pellicle mounts 310a, 310b, 310c (collectively referred to as 310), and multiple pellicles 301a, 301b, 301c (collectively referred to as 301). The pellicle heater 320 provides radiation 330 that irradiates the pellicle 301a. A portion of the radiation 330 that irradiates the pellicle 301 is not absorbed by the pellicle 301a, and after passing through the pellicle 301a, attenuated radiation 332 irradiates the pellicle 302a. A portion of the attenuated radiation 332 is not absorbed by the pellicle 301b, and after passing through the pellicle 301b, a second attenuated radiation 334 irradiates the pellicle 301c. In this manner, multiple pellicles 301 can be cleaned using a single pellicle heater 320. The multiple pellicles 301 may each be of a different type (i.e., constructed from a different material) such that the wavelength of radiation 330 absorbed by the first illuminated pellicle 301a is preferably different from the wavelengths of radiation 332, 334 absorbed by the other pellicles 301b, 301c. The pellicle mount 310 may include a mechanism to allow the pellicle mount 310 to move position to vary the order in which the pellicles 301 (held in the pellicle mount 310) are illuminated.

[0116] [000115] As would be apparent to one of ordinary skill in the art, any combination of exemplary pellicle cleaning tools 330a, 300b, 300c, 300d is contemplated. For example, a single pellicle 301 may be mounted on a pellicle mount 310 in a substantially horizontally aligned manner and illuminated with radiation 330 from multiple pellicle heaters 320 (i.e., exemplary pellicle cleaning tools 300a, 300c may be combined). Additionally, mirrors 341, 342 may be provided to reflect attenuated radiation 332 to illuminate a second side of the pellicle 301.

[0117] [000116] Referring again to FIG. 2, a method of using the pellicle cleaning tool 200 includes mounting the pellicle 201 onto the pellicle mount 210 (in instances where the cleaning tool 200 includes the pellicle mount 210).

[0118] [000117] As mentioned above, a lithographic apparatus (such as lithographic apparatus LA) may include a pellicle cleaning tool 200. In such a lithographic apparatus, the pellicle 201 may already be in a fixed position (e.g., fixed using a pellicle frame, such as pellicle frame 16, and does not require fixation to a pellicle mount 210).

[0119] [000118] A method of using the pellicle cleaning tool 200 includes heating the pellicle 201 with radiation 220 from the pellicle heater 230 to induce thermomechanical vibration. In an example where the pellicle heater 230 is a laser, the thermomechanical vibration is induced by irradiating the pellicle 201 with laser light. The pellicle 201 may be heated periodically, i.e., the pellicle heater may be pulsed. The thermomechanical vibration may provide sufficient energy and momentum to loosen particles from the surface of the pellicle 201. In other words, the pellicle 201 may be cleaned.

[0120] [000119] As noted above, the pellicle cleaning tool 200 may include an enclosure 226 (and optionally a load lock) in which a low ambient pressure is provided. The pellicle 201 may be removably secured within the enclosure 226 (or load lock) to a pellicle clamp 210 or other (e.g., a temporary position within the load lock) prior to irradiation by the pellicle heater 220. The ambient pressure within the enclosure 226 (or load lock) may then be reduced. In addition to the cleaning effect caused by the induced thermo-mechanical vibrations, the reduction in ambient pressure may also remove contaminants from the pellicle.

[0121] [000120] The cleaning effect may be greater in areas of the pellicle 201 near the irradiated area (i.e., the area irradiated with radiation 230). In other words, a majority of the contaminants may be removed from the surface of the pellicle 201 in the non-irradiated areas. Thus, radiation 230 may irradiate various areas of the pellicle 201 sequentially (by moving the pellicle heater 220, pellicle mount 210, or using other optics) or simultaneously (by using more than one pellicle heater 220 or optics). The amplitude of the thermo-mechanical vibrations may be smaller (and therefore the cleaning effect reduced) in areas of the pellicle further away from the irradiated area.

[0122] [000121] The method may further include irradiating additional areas of the pellicle 201. For example, the position of the pellicle 201 relative to the pellicle heater 220 may be changed and / or the pellicle heater 220 may be adjusted so that the radiation 230 irradiates different areas of the pellicle 201.

[0123] [000122] A method of using the pellicle cleaning tool 200 may further include irradiating (simultaneously or sequentially) the pellicle 201 with multiple wavelengths of radiation 230. For example, the pellicle 201 may be first irradiated with a first wavelength of radiation 230 to remove a first type of contamination, and then the pellicle 201 may be irradiated with a second wavelength of radiation 230 to remove a second type of contamination. The multiple wavelengths of radiation 230 may be provided by adjusting the characteristics of a single pellicle heater 220, or alternatively, may be provided by providing multiple pellicle heaters 220 to the pellicle cleaning tool 200, with each pellicle heater 220 providing a different wavelength of radiation 230.

[0124] [000123] Figure 4 illustrates an exemplary pellicle 401 with conceptual regions 411-419 illustrated. Regions 411-419 are merely representational and may not be marked on the surface of pellicle 401 itself. Pellicle 401 may be pellicle 201 that is to be cleaned by pellicle cleaning tool 200. For purposes of explanation, pellicle 401 will be considered to be contaminated with a uniform level of contamination in each of regions 411-419 prior to cleaning.

[0125] [000124] First, a central region 415 of the pellicle 401 may be irradiated (with radiation 230). The radiation 230 may induce a first thermo-mechanical vibration. The first thermo-mechanical vibration may provide a cleaning effect. The cleaning effect of the irradiated region (i.e., central region 415) may be less than the cleaning effect of the other regions 411-419. Thereafter (or simultaneously), a second region, such as region 411, may be irradiated to induce a second thermo-mechanical vibration. The second thermo-mechanical vibration may provide an additional cleaning effect. For example, the second thermo-mechanical vibration may produce a more significant cleaning than that of the central region 415 caused by the first thermo-mechanical vibration.

[0126] [000125] Not all areas of the pellicle 401 may be irradiated (with radiation 230). For example, area 411 may be irradiated first. The pellicle heater 220 may then be moved to irradiate areas 413, 417, and 419 in sequence. In this manner, each area of ​​the pellicle 401 is cleaned by thermo-mechanical vibration, but some areas (e.g., central area 415 or edge area 414) are cleaned by thermo-mechanical vibration resulting from some irradiated areas. However, it will be appreciated that the number of irradiated areas and the order of their irradiation may vary depending on the particular application. In instances where each of the irradiated areas is irradiated in sequence by the same heater, the radiation and / or heater may be described as scanning the entire pellicle 401.

[0127] [000126] The pellicle cleaning tool 200 and method of pellicle cleaning can be calibrated (i.e., the properties of radiation 230 and other aspects of the pellicle cleaning tool 200 can be optimized) for a particular type of pellicle 201 (or component or type of component). For example, the wavelength / frequency of the beam of radiation 230, the frequency of the multiple pulses, the length of time each pulse is applied, and / or the shape / profile can be optimized. Calibration can also provide a minimum length of time required for a cleaning effect (by the pellicle cleaning tool 200) to remove contaminants, or a maximum length of time (or temperature) beyond which the pellicle 201 may be damaged.

[0128] [000127] Calibration can use experimental data. For example, multiple pellicles are contaminated. The contamination can be at a similar level and one or more artificial contaminants can be used. Exemplary artificial contaminants include zirconium boride (ZrB2) or silicon dioxide (SiO2). Two or more artificial contaminants can be used to contaminate each pellicle 201 to provide both conductive and non-conductive contamination. The pellicle cleaning tool 200 can be used to clean the contaminated pellicles. One or more characteristics of the pellicle cleaning tool 200, such as the frequency of the radiation 230, can be varied as each of the contaminated pellicles is cleaned. By comparing the contamination of the contaminated pellicles before and after cleaning, the cleaning effectiveness achieved by the pellicle cleaning tool 200 can be measured as a function of the varied characteristics.

[0129] [000128] Calibration may involve irradiating the pellicle 201 with radiation 230 until wrinkles appear. For some pellicles, a minimum length of time has been found to be 20 s, with a maximum length of time being 1 hour or more.

[0130] [000129] The experimental data collected during calibration can be used as input to a predictive model. The predictive model can be used to calibrate the pellicle cleaning tool 200 for cleaning a pellicle 201 similar to one or more pellicles used to collect the experimental data. Alternatively, the predictive model can be used to calibrate the pellicle cleaning tool 200 for cleaning a pellicle 201 even if the pellicle 201 does not resemble any of the pellicles used to collect the experimental data. In other words, the experimental data can be used to extrapolate and predict optimal characteristics of the pellicle cleaning tool 200 for a pellicle 201 (or type of pellicle 201) that has not been previously cleaned.

[0131] [000130] Table 1 shows an exemplary set of properties that were tested in the calibration of pellicle cleaning tool 200. The pellicle cleaning tool 200 used to test the conditions shown in Table 1 included an infrared (IR) laser with a maximum power of 200 W.

[0132] [Table 1]

[0133] [000131] Table 2 shows the cleaning results corresponding to the conditions shown in Table 1. The pellicle 201 tested in these results was constructed from a metal silicide film and was contaminated with an artificial contaminant (ZrB2) prior to testing. "PRD Total" indicates the percentage and number of all generated contaminants greater than 1 μm in diameter that were removed in all areas of the pellicle 201. PRD and generated contaminants represent contamination that arose in the pellicle generation process, in other words, contaminants that were not artificially introduced. "ZrB2 Total", "ZrB2 Unexposed and ZrB2 Exposed" indicate the percentage and number of artificial contaminants greater than 1 μm in diameter that were removed in all areas, non-irradiated areas, and irradiated areas of the pellicle 201, respectively. Not all contaminants are spherical. For non-spherical contaminants, diameter (as used herein) represents the diameter of a sphere that would have the same volume or cross-sectional area as the non-spherical contaminant.

[0134] [Table 2]

[0135] [000132] Table 2 shows that of the parameters tested, the parameters used in test number 3 were the ones that gave the best cleaning.

[0136] [000133] Figure 5 shows an exemplary graph illustrating the number of contaminants present on the pellicle 201 used in Test 3 as a function of contaminant size before and after cleaning with the pellicle cleaning tool 200. Also shown is the cleaning rate (i.e., the percentage of contaminants removed by cleaning). Figure 5 shows that cleaning is particularly effective for larger contaminants.

[0137] [000134] Figure 6A shows a graph (similar to the graph shown in Figure 5) restricted to data from the illuminated area.

[0138] [000135] Figure 6B shows a graph (similar to the graph shown in Figure 5) restricted to data from outside the illuminated area.

[0139] [000136] Both Figures 6A and 6B show that the cleaning effect of the pellicle cleaning tool 200 is more effective outside the illuminated area.

[0140] [000137] The pellicle cleaning tool 200 (and possibly other apparatus including a pellicle cleaning tool) may be controlled by a computer system. For example, the computer system may monitor contamination of the pellicle 16 during use in the lithographic apparatus LA. The computer system may identify when contamination of the pellicle 16 reaches an unacceptable level and transfer the pellicle 16 to the pellicle cleaning tool 200. As another example, the computer may monitor contamination of the pellicle 201 in the pellicle cleaning tool 200 and adjust the pellicle heater 220 accordingly. The pellicle 201 may have first and second contaminated regions. The computer may identify these two contaminated regions and control the pellicle cleaning tool 200 to irradiate an area of ​​the pellicle 201 near the first contaminated region. The computer may monitor the contamination level of the first contaminated region and, once it has determined that the first region is cleaned, adjust the pellicle cleaning tool 200 such that an area of ​​the pellicle 201 near the second contaminated region is irradiated with radiation 230. The pellicle cleaning tool 200 can then continue irradiating an area of ​​the pellicle 201 near the second contaminated area until the computer determines that the second contaminated area has been cleaned.

[0141] [000138] Figures 7 and 8 show schematic diagrams of an exemplary configuration 700 for cleaning a pellicle 702 according to the principles and techniques described above. As best seen in Figure 7, the configuration 700 includes a laser 704 that provides a laser beam to a laser collimator 706. The laser collimator 706 provides a collimated laser beam 708 to a housing 710. The housing 710 may include optical components to further condition the laser beam 708 before it is incident on the pellicle 702. The housing 710 may also house one or more other of the components of the configuration 700 described below. The laser beam 708 passes through a window 712 that separates the optical box 710 from a container 714 that contains the pellicle 702. The container 714 may be a vacuum container. The window 712 may be mounted to the container 714 and may be mounted using any suitable means. For example, the window 712 may be mounted to the container 714 using bolts. Advantageously, existing containers 714 in operation may already include threaded holes suitable for mounting window 712, making configuration 700 suitable for retrofitting to existing tools and equipment. Housing 710 may be mounted to the window, again using any suitable means. Housing 710 may be mounted to window 712 separately.

[0142] [000139] The portion of the laser beam 708 that passes through the pellicle 702 may be incident on a beam dump 716. A thermal radiation sensor 718, which may be, for example, a pyrometer, is positioned to detect thermal radiation emitted from the pellicle 702. Detection of the thermal radiation using the thermal radiation sensor 718 may enable process control. For example, the power, duration, frequency, etc. of the laser radiation provided by the system may be adjusted in response to the thermal radiation emitted from the pellicle 702. An optical sensor 720 (e.g., a camera) is configured to image the surface of the pellicle 702 on which the laser beam 708 is present to enable alignment of the thermal sensor 718 and the laser beam 708.

[0143] [000140] A laser interlock safety mechanism 722 can be provided to automatically shut off the laser beam 708 during pellicle swap using, for example, a load lock 724.

[0144] [000141] Figure 8 illustrates exemplary components of configuration 700 in greater detail. From Figure 8, it can be seen that a second beam dump 722 is positioned to receive a reflected portion 724 of the laser beam 708. The second beam dump 722 may be contained within the housing 710.

[0145] [000142] An illuminator 726 (eg, one or more LEDs) may be provided to illuminate the pellicle 702 for a photosensor 720 (not visible in FIG. 8).

[0146] [000143] As discussed above, components associated with a lithographic process (other than a pellicle) may be cleaned with a cleaning tool. Other components (i.e. components other than the one being cleaned) may be provided with a cleaning tool to enable cleaning of the component. As an example, a reticle backside inspection tool (i.e. a tool for inspecting the backside of a patterning device such as a patterning device MA) may be provided with a cleaning tool for cleaning the patterning device. Additionally or alternatively, a device for handling a patterning device MA may be provided with a cleaning tool.

[0147] [000144] As another example, a reticle exchange device (ie a device for handling a patterning device) may be equipped with a cleaning tool to allow cleaning of parts of the patterning device MA and / or the support structure MT.

[0148] [000145] As another example, a wafer handling system may be equipped with a cleaning tool to enable cleaning of the wafer (i.e., substrate W).

[0149] [000146] As another example, a cleaning tool may be integrated with the lithographic apparatus LA to allow cleaning of components within the lithographic apparatus LA. For example, the lithographic apparatus LA may include one or more members for controlling the area of ​​the substrate W that is exposed to the EUV radiation beam B. Such members may be cleaned by the cleaning tool. Additionally or alternatively, a gas outlet may direct gas to the surface of the reticle and / or pellicle to prevent the accumulation of contaminants. Such a gas outlet may be cleaned by the cleaning tool.

[0150] [000147] Referring again to FIG. 2, in addition to or as an alternative to the heater 220, the cleaning system 200 can include an ion source. The ion source can provide a cleaning effect, referred to as ion beam sputtering, described below in connection with FIG. 9A and FIG. 9B. The cleaning effect provided by the ion source can be implemented as an alternative to the cleaning effect provided by the heater 220. Alternatively, the cleaning effect provided by the ion source can be implemented in addition to the cleaning effect provided by the heater 220. In examples where the heater 220 and the ion source are used to provide a cleaning effect, the heater 220 and the ion source can be used in any order. For example, the ion source can be used first (to clean the component 201) and the heater 220 can be used second. The ion beam sputtering can increase the effectiveness of subsequent cleaning (e.g., cleaning provided by the heater 220) by reducing the strength of the bonding forces binding the contaminants to the component 201. Another advantage is that by using a combination of cleaning techniques (e.g., heating to produce thermomechanical vibration and irradiating with ions to induce sputtering), inadvertent damage caused by one cleaning technique can be mitigated and / or entirely avoided. For example, a pellicle can be damaged by thermomechanical vibration (caused by heating as described above). By first using ion beam sputtering to reduce the binding forces (binding contaminants to the pellicle), the effectiveness of subsequent thermomechanical vibration can be improved. Thus, less heating is required to achieve a given cleaning effect, which can reduce (or reduce the likelihood of) damage to the pellicle compared to cleaning using heating alone.

[0151] [000148] Figure 9A shows a first schematic diagram of a component associated with a lithography process being cleaned. Figure 9A shows a system 901 including a component associated with a lithography process 910 that is contaminated with a contaminant 930. Ions 910 are incident on the component 920.

[0152] [000149] The ions 910 may be ions of a noble gas element. Advantageously, the ions of a noble gas element may reduce (or entirely avoid) chemical reactions between the ions 910 and the component 920. For example, the ions 910 may be argon positive ions, i.e., argon atoms that have "lost" one or more electrons due to ionization. Alternatively, the ions 910 may be helium or neon positive ions. Advantageously, the helium or neon positive ions have smaller atomic diameters (or radii) than the argon positive ions, reducing the chance of side scattering. In other words, the use of helium or neon positive ions may provide more control and less harmful damage (to the component 920) and reduce the risk of implantation compared to other ions. The ions 910 may be one of a number of ions.

[0153] [000150] The ions 910 may be provided by an ion source. For example, the ion source may be an ion gun such as those used in ion milling. Alternatively, the ion source may be any suitable ion source known in the art. By way of example only, the ion source may be a multimode gas cluster ion source manufactured by Kratos Analytical.

[0154] [000151] Component 920 may be any component associated with a lithography process (as discussed above). As an example, component 920 may be a pellicle. Component 920 has a first side 921 and a second side 922. The component is made up of atoms, such as atom 923. Although FIG. 9A shows component 920 (and contaminant 930) having a simplified arrangement of atoms, it will be appreciated that this is merely by way of example and that the method illustrated in FIG. 9A (and FIG. 9B, discussed below) may be applied to components having more complex arrangements of atoms.

[0155] [000152] A second side 922 of component 920 is contaminated with contaminant 930. Contaminant 930 is made up of atoms, such as atom 931. Bonding forces bond atoms of contaminant 930 that are in close proximity to component 920, such as atom 932, to atoms of component 920. The bonding forces may be due to van der Waals forces, for example.

[0156] [000153] Ion 910 is directed towards a first side 921 of component 920 in a direction indicated by arrow 912. In other words, ion 910 irradiates a first surface 921 of component 920. The ion may travel through a portion of component 920. An intermediate position 914 (and corresponding direction) of ion 910 is shown, illustrating that ion 910 travels between atoms on the surface of first side 921 of component 920.

[0157] [000154] The ion 910 collides with a first atom 924 of the component 920 in a first collision 941 (indicated by an asterisk). In the first collision 941, a momentum exchange occurs between the ion 910 and the first atom 924, resulting in the first atom 924 gaining momentum. The first atom 924 gains sufficient momentum to move from its original position (e.g., from a lattice site for atoms arranged in a crystal structure). Such movement of the first atom 924 can be said to cause the first atom 924 to be "kicked out." In other words, the ion 910 causes a cascade, also called a collision cascade.

[0158] [000155] The first atom 924 collides with a second atom 925 of the component 920 in a second collision 942. Similar to the first collision 941, the second collision 942 also results in a momentum exchange between the first atom 924 and the second atom 925, resulting in a momentum gain for the second atom 925. The second atom 925 gains sufficient momentum to move from the original position of the second atom 925.

[0159] [000156] The second atom 925 (of the component 920) collides with the atom 936 of the contaminant 930 in a third collision 943. In the third collision 943, a momentum exchange occurs between the second atom 925 and the atom 936 of the contaminant 930. The atom 936 of the contaminant 930 gains sufficient momentum to move from its original position (to a position away from the second surface 922 of the component 920). As a result, the binding force that attracts the atom 936 (and the contaminant 930) to the second surface 922 of the component 920 is reduced.

[0160] [000157] The contaminants 930 may be sputtered. In other words, the contaminants 930 may be released from the second side 922 of the component 920 due to a reduction in the bonding force. In other examples, the contaminants 930 are not released and remain on the second side 922 of the component 920, but the strength of the bonding force may be reduced (compared to without / before ion beam sputtering). In examples where the contaminants 930 are not released by sputtering, the contaminants 930 may then be removed using other cleaning methods, for example, by applying heat as described above.

[0161] 9A shows a cascade of three collisions (i.e., first collision 941, second collision 942, and third collision 943), it will be appreciated that any number of collisions are possible before a collision (such as collision 943) involving an atom of the contaminant 930. In some examples, the ion 910 may travel straight through the component 920 (i.e., without colliding with an atom of the component 920) and the ion 910 itself may collide with an atom of the contaminant 930 (such as atom 936).

[0162] [000159] It will also be appreciated that the ions 910 may interact with the first surface 921 of the component at any suitable region (of the first surface 921) using any suitable angle. For example, the direction 912 of the ions 910 may be perpendicular to the first surface 921 and directed to a region of the first surface 921 opposite a region of the second surface 921 that is contaminated (e.g., by the contaminant 930). As an alternative example, the direction 912 of the ions 910 may be at an alternative angle (i.e., not perpendicular) to the first surface 921 and directed to a region of the first surface 921 such that the ions 910 are directed toward a region of the second surface 921 that is contaminated. In other words, the direction 912 of the ions 910 and the region of the first surface 921 on which the ions are incident may be selected such that the ions 910 (and the cascade caused by the ions 910) are directed to a region of the second surface 921 that is contaminated.

[0163] [000160] Although FIG. 9A shows a single ion 910, it will be appreciated that any suitable number of ions 910 may be used to achieve the desired cleaning effect (i.e., whether it is removal of the contaminant 930 by sputtering or reduction in the bonding forces binding the contaminant 930 to the second side 922 of the component 920). Similarly, the properties of the ions 910 may be selected to achieve the desired cleaning effect. For example, the energy of each ion 910 and / or the total dose / current provided by all ions 910 may be selected to achieve the desired cleaning effect. An energy of about 0.1 keV to 10 keV may be a suitable energy for each ion 910. A current of about 1 nA to 1 mA may be a suitable total current. The properties of the ions 910 may be selected to provide sufficient energy to cause a cascade of atoms within the component 920. The properties of the ions 910 may be selected to prevent damage to the component 920. For example, the properties of the ions 910 may be selected to ensure that the cascade of atoms in the component 920 is of an appropriate size (i.e., an appropriate number of atoms are ejected) to reduce and / or avoid damage to the component 920. Examples of damage that may occur if the properties of the ions 910 are not selected appropriately include unevenness of the surface of the component 920, thinning of the component 920, and / or degradation of the structure of the component 920. Such damage may affect the performance of the component 920. In an example where the component 920 is a pellicle, the damage may adversely affect key performance indicators of imaging. The energy of each ion 910 may be selected to ensure that each ion 910 has sufficient energy to eject a single atom in the component 920.

[0164] [000161] The first side 921 of the component 920 can be irradiated with ions 910 in one or more regions. For example, a region (on the second side 922 of the component 920) can be identified as contaminated and a cleaning effect can be achieved in the region of the second side 922 by irradiating the corresponding region of the first side 921 with ions 910. The contaminated region can be identified using any suitable device and / or technique known in the art, for example optical devices and / or techniques. Additionally or alternatively, it is also possible to clean multiple regions of the second side 922 by sequentially irradiating corresponding regions of the first side 921. In this way, the entire surface of the second side 922 can be cleaned. In other words, the ions 910 (and / or the ion source) can scan the component 920 in a similar manner as described above with reference to the heater. This can be referred to as a raster scan.

[0165] [000162] The component 920 may have any coefficient of thermal expansion. In other words, the coefficient of thermal expansion of the component 920 may not affect cleaning by ion bombardment.

[0166] [000163] Figure 9B shows a second schematic diagram of a component associated with a lithography process being cleaned. Figure 9B shows a system 902 including a component associated with a lithography process 910 that is contaminated with contaminant 930. Various aspects of system 902 (including component 920 and contaminant 930) are substantially similar to system 901 and are similarly numbered. Ions 950 are irradiating component 920.

[0167] [000164] Except for the direction and starting position, ion 950 may be substantially similar to ion 910.

[0168] [000165] The ions 950 are directed towards the second side 922 of the component 922 (i.e. the side contaminated with the contaminant 930) in a direction indicated by an arrow 952. In other words, the ions 950 irradiate the second surface 922 of the component 920. The direction 952 of the ions 950 may be at an angle (measured relative to a plane defined by the second side 922 of the component 920) that is less than the perpendicular angle discussed with respect to the system 901. In other words, the angle may be an oblique angle. Due to the relative thickness of the contaminant 930 compared to the component 920, the ions 950 may not be able to travel through the contaminant 930 (or cause a cascade through the contaminant 930). The angle need therefore be small enough to ensure that the area of ​​contaminant 930 in contact with component 920 (such as the area occupied by atoms 932, 938) is irradiated with ions 950 (and not blocked by the contaminant 930 itself). Similar to the properties of ions 950 (discussed above with respect to FIG. 9A ), the properties of ions 950 may be selected to achieve a desired cleaning effect and / or to prevent damage to component 920.

[0169] [000166] Ion 950 collides with atom 938 of contaminant 930 in collision 961 (indicated by an asterisk). In the first collision 961, momentum exchange occurs between ion 950 and atom 938, resulting in atom 938 gaining momentum and being ejected. As a result, the binding force attracting atom 938 (and contaminant 930) to second surface 922 of component 920 is reduced.

[0170] [000167] Similar to system 901, system 902 can also sputter contaminants 930 and / or reduce the strength of bonding forces.

[0171] [000168] The characteristics of the ions 950 may be selected to provide optimal cleaning effectiveness and / or to minimize damage to the component 920. For example, the energy of the ions 950 may be selected to ensure that a single collision occurs (i.e., so that a single atom of the contaminant 930 is dislodged).

[0172] [000169] For components that are contaminated on a first side and a second side, the component may be cleaned using a single ion source that cleans the first side shown in Figure 9A and the second side shown in Figure 9B. Alternatively, the component may be cleaned a first time on the first side shown in Figure 9A, and the component and / or the ion source may be repositioned and the component cleaned a second time on the second side shown in Figure 9A. Similarly, the component may be cleaned a second time using the method shown in Figure 9B.

[0173] [000170] Although cleaning tool 200 has been described above with respect to cleaning component 201, cleaning tool 200 may also be used to test the structural integrity of the component. Thus, cleaning tool 200 may also be described as testing tool 200. The component tested by testing tool 200 may be a pellicle or any other component associated with a lithography process. For example, tool 200 may be used to test, for example, the ultimate tensile strength of a membrane of a pellicle. When used to test the structural integrity of component 201, testing tool 200 may be used in the same or similar manner as when used to clean component 201.

[0174] [000171] When used to test the structural integrity of component 201, thermo-mechanical vibrations (caused by heat provided by radiation 230) may damage component 201 if the structural integrity is below a required value (i.e., a structural integrity threshold). As an example, a membrane of a pellicle may be damaged if the pellicle does not have the required structural integrity. By testing in this manner, components with structural integrity below a required value (i.e., defective components) may be screened. Advantageously, such testing allows for identification of defective components. As a result, such testing may prevent defective components from being installed in, for example, a lithography apparatus, thereby avoiding downtime periods. In the example where component 201 is a pellicle, testing the pellicle in this manner (thereby preventing a defective pellicle from being used in the lithography apparatus) prevents a defective pellicle from damaging a reticle if it is damaged while in place in the lithography apparatus.

[0175] [000172] The thermo-mechanical vibrations (and the corresponding one or more mechanical waves) can propagate across the surface of the component 201. For example, the one or more mechanical waves can test the structural integrity of the pellicle at the corners of the film that would not have been tested using prior art methods. Advantageously, the test tool 200 can be used to screen for defective components that would not have been identified otherwise. In particular, prior art test methods require clamping the pellicle at the corners, which may result in the corners not being properly tested. Also, when testing a pellicle using prior art test methods, the pellicle frame may prevent the entire film from deforming sufficiently. For example, areas near the pellicle frame may not deform to the same extent as other areas of the film. As a result, prior art test methods may not be able to properly test areas near the pellicle frame. The presently described techniques allow for testing of the structural integrity of the entire pellicle, including the corners and / or portions near the pellicle frame. In particular, the presently described techniques allow for testing of the structural integrity without clamping the corners.

[0176] [000173] The radiation 230 used to test the structural integrity of the component 201 may have substantially the same characteristics as the radiation used to clean the component 201. Additionally or alternatively, the characteristics of the radiation (used for testing) may be selected to increase or optimize the velocity amplitude of one or more mechanical waves induced in the component 201. Increasing the velocity amplitude increases the stress amplitude caused by the one or more mechanical waves. As an example, the radiation used for testing has a narrower slit width than the slit width of the radiation used for cleaning. A narrower slit width can generate waves with shorter wavelengths, higher frequencies and therefore higher maximum velocity amplitudes. Since the stress amplitude corresponds to the maximum velocity amplitude, reducing the slit width (compared to using a tool for cleaning) can increase the stress amplitude.

[0177] [000174] Additionally or alternatively, the radiation 230 used to test the structural integrity of the component 201 may have increased pulse energy or spot size. Such radiation 230 may increase the power of heat absorbed by the tool, which may be useful for testing the reliability of the component 201.

[0178] [000175] The cleaning tool 200 may include additional or alternative components to configure the tool for use as a test tool. For example, the tool 200 may include additional or alternative optical elements.

[0179] [000176] In some examples, the tool 200 can be operated to provide radiation 230 having a first slit width and radiation 230 having a second slit width. For example, the tool 200 can clean a first component by heating the first component with radiation 230 having the first slit width. The tool can then clean the component (the first component or the second component) by heating the component with radiation having a second slit width. The second slit width can be the same as the first slit width, narrower than the first slit width, or wider than the first slit width.

[0180] [000177] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it will be appreciated that the lithographic apparatus described herein have other applications, such as in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0181] [000178] Although specific reference is made herein to embodiments of the invention in relation to lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus may be generally referred to as lithography tools. Such lithography tools may use vacuum or ambient (non-vacuum) conditions.

[0182] [000179] Where the context permits, 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 others. Furthermore, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be understood that such description is merely for convenience and that such actions would in fact result from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., and that in performing the actions, actuators or other devices may interact with the physical world.

[0183] [000180] While specific embodiments of the invention have been described above, it will be appreciated that the invention can be practiced otherwise than as described. The above description is illustrative and not limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the invention as described without departing from the scope of the claims set out below.

Claims

1. 1. A cleaning system for cleaning a component associated with a lithography process, comprising: to induce thermomechanical vibrations in said component; and / or To induce sputtering of contaminants present on said component, A cleaning system comprising at least one radiation emitter configured to irradiate an area of ​​the component in use.

2. 1. A system for testing the structural integrity of a component associated with a lithography process, comprising:

13. A system comprising: at least one radiation emitter configured, in use, to irradiate an area of ​​the component to induce thermo-mechanical vibration in the component.

3. The system of claim 1 or 2, wherein the component is a pellicle.

4. The system of claim 1 , further comprising a holder configured to hold the component.

5. 5. The system of claim 1, wherein the at least one radiation emitter comprises a heater configured to irradiate an area of ​​the component, in use, to induce thermo-mechanical vibration in the component.

6. The system of claim 5 , wherein the heater is a laser.

7. 7. The system of claim 5 or 6, wherein the radiation provided by the heater has a frequency between 300 GHz and 4300 THz.

8. 8. The system of claim 5, wherein the radiation provided by the heater has an average power of 1 mW to 200 W.

9. 9. The system of claim 5, wherein the radiation provided by the heater is pulsed.

10. The system of claim 9 , wherein the radiation has a pulse frequency of from 1 Hz to 1 MHz.

11. 11. The system of claim 9 or 10, wherein each pulse of radiation has a duration of from 1 fs to 10 μs.

12. 12. The system of claim 4, wherein the holder is positioned such that contaminants to be cleaned from the component are removed from the vicinity of the component under the force of gravity.

13. 13. The system of claim 5, wherein the heater is configured to provide a plurality of beams of radiation.

14. The system of claim 13 , wherein the heater comprises a plurality of heaters for generating one or more of the plurality of radiation beams.

15. 15. A system according to claim 13 or 14, wherein the heater comprises one or more beam splitting and / or redirecting optics for generating one or more of the plurality of radiation beams.

16. the holder is one of a plurality of holders; 16. A system according to any one of claims 5 to 15 dependent on claim 4, wherein the heater is configured to heat an area of ​​each of a plurality of components in use, each of the plurality of components being held in one of the plurality of holders.

17. 17. A system according to claim 16 when dependent on any one of claims 13 to 15, wherein, in use, different ones of the plurality of radiation beams are configured to be incident on different ones of the plurality of components.

18. The system of claim 16 , wherein the heater is configured to heat different ones of the plurality of components with different wavelengths.

19. 19. The system of any preceding claim, wherein the at least one radiation emitter comprises an ion source configured, in use, to irradiate an area of ​​the component with ions to induce sputtering of contaminants present on the component.

20. 20. The system of claim 19, wherein the ion source is configured to, in use, irradiate an area of ​​a first side of the component with ions to induce sputtering of contaminants present on a second side of the component.

21. 21. The system of claim 19 or 20, wherein the ion source is configured to irradiate an area of ​​the first side of the component with ions, in use, to induce sputtering of contaminants present on the first side of the component.

22. The at least one radiation emitter comprises: a heater configured, in use, to heat an area of ​​the component to induce thermo-mechanical vibration in the component; and an ion source configured, in use, to irradiate an area of ​​the component with ions to induce sputtering of contaminants present on the component; 22. The system of claim 1 , comprising:

23. 23. The system of claim 3, further comprising a housing, the radiation emitter and the holder being contained within the housing.

24. The system of claim 23 , wherein the enclosure comprises a load lock chamber.

25. 25. The system of claim 23 or 24, further comprising a vacuum pump.

26. 26. The system of claim 1 further comprising a gas exhaust for removing contaminants.

27. 27. The system of claim 1, further comprising metrology for measuring radiation emitted by the radiation emitter.

28. 28. The system of claim 1, further comprising metrology for measuring contamination on or removed from the component.

29. 29. The system of any of claims 1 to 28, comprising an adjuster for adjusting a slit width of the radiation between a first slit width and a second slit width.

30. 1. A method for cleaning a component associated with a lithography process, comprising the steps of: to induce thermomechanical vibrations in said component; and / or To induce sputtering of contaminants present on said component, illuminating an area of ​​the component.

31. 13. A method of testing the structural integrity of a component associated with a lithographic process, the method comprising irradiating an area of ​​the component to induce thermo-mechanical vibrations in the component.

32. 32. The method of claim 30 or 31, wherein irradiating the region of the component comprises heating the region of the component to induce thermo-mechanical vibration in the component.

33. 33. The method of claim 32, wherein the heating comprises providing one or more pulses of a pulse heater.

34. 34. The method of claim 32 or 33, wherein heating the region of the component is performed for a time period of from 20 seconds to 1 hour.

35. 35. The method of claim 32, 33, or 34, wherein heating the component by radiation further comprises heating a second region of the component for from 20 seconds to 1 hour.

36. 36. A method according to any one of claims 30 to 35, wherein irradiating an area of ​​the component comprises irradiating the area of ​​the component with ions to induce sputtering of contaminants present on the component.

37. 37. The method of claim 36, wherein irradiating an area of ​​the component comprises irradiating an area of ​​a first side of the component with ions to induce sputtering of contaminants present on a second side of the component.

38. 38. The method of claim 36 or 37, wherein irradiating an area of ​​the component comprises irradiating an area of ​​the first side of the component with an ion source to induce sputtering of contaminants present on the first side of the component.

39. The method comprises: illuminating the component with radiation having a first slit width; irradiating the second component with radiation having a second slit width; 39. The method of any of claims 30 to 38, comprising:

40. The method comprises: testing the structural integrity of the component by irradiating the component with radiation having a first slit width; narrowing the slit width of the radiation from the first slit width to a second slit width; cleaning the component by irradiating the component with radiation having the second slit width; 39. The method of any of claims 30 to 38, comprising:

41. A controller configured to control a system according to any of claims 1 to 29 to carry out a method according to any of claims 30 to 40.

42. A component that has been cleaned or tested according to the method of any one of claims 30 to 40.

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