Cover film and method of using same

Abstract

A pellicle includes a frame, a membrane, and a gasket. The frame includes a check valve, wherein the check valve is configured to allow gas to flow from an interior of the pellicle to an exterior of the pellicle. A bottom surface of the frame defines a recess. The membrane extends across the frame. And the gasket is configured to be matched in the groove. According to the protective film and the method for using the protective film in the embodiment of the invention, the service life of the mask can be prolonged.

Description

[0001] The present invention is a divisional application of the invention patent application with application number 201710545410.8 and invention name “Protective Film” filed on July 6, 2017. Technical Field

[0002] Embodiments of the present invention relate to a protective film and a method of using the protective film. Background Art

[0003] A pellicle protects a photomask (also called a reticle) from particles, reducing errors during the transfer of the pattern from the mask to the wafer. The pellicle consists of a frame attached to the mask and a film extending across the frame. In some implementations, an adhesive secures the frame to the mask.

[0004] In some implementations, the pellicle remains on the mask during the photolithography process. When the pellicle remains on the mask during the photolithography process, the intensity of light passing through the pellicle is reduced due to absorption and scattering of light incident on the pellicle. In some implementations, the pellicle is removed from the mask prior to a photolithography process, such as extreme ultraviolet (EUV) lithography. A cleaning process is used to remove the adhesive used to secure the frame to the mask. Summary of the Invention

[0005] Embodiments of the present invention are directed to a protective film and a method of using the protective film, which can extend the service life of the mask.

[0006] In certain embodiments, a diaphragm includes a frame, a membrane, and a gasket. The frame includes a check valve configured to allow gas to flow from an interior of the diaphragm to an exterior of the diaphragm, and a bottom surface of the frame defines a groove. The membrane extends across the frame. The gasket is configured to fit within the groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The various aspects of the present invention will be best understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0008] Figure 1 is a schematic diagram of a lithography machine according to some embodiments.

[0009] Figure 2A is a cross-sectional view of a pellicle separated from a mask according to some embodiments.

[0010] Figure 2B is a cross-sectional view of a pellicle securely secured to a mask according to some embodiments.

[0011] Figure 3A is a cross-sectional view of a membrane check valve in a configuration allowing gas flow, according to certain embodiments.

[0012] Figure 3B is a cross-sectional view of a membrane check valve in a configuration that blocks gas flow, according to certain embodiments.

[0013] Figure 4 is a cross-sectional view of a pellicle securely secured to a mask according to some embodiments.

[0014] Figure 5 is a cross-sectional view of a pellicle separated from a mask according to some embodiments.

[0015] Figure 6A 、 Figure 6B ,and Figure 6C is a cross-sectional view of a demounting process for a pellicle according to certain embodiments.

[0016] Figure 7 is a flow chart of a method of using a pellicle, according to certain embodiments. DETAILED DESCRIPTION

[0017] The following disclosure provides many different embodiments or examples for implementing the different features of the provided subject matter. Specific examples of components, values, operations, materials, arrangements, etc. are described below to simplify the embodiments of the present invention. Of course, these are merely examples and are not intended to be limiting. It is contemplated that there are other components, values, operations, materials, arrangements, etc. For example, the following description in which a first feature is formed "on" or "on" a second feature may include an embodiment in which the first feature and the second feature are formed to be in direct contact, and may also include an embodiment in which an additional feature may be formed between the first feature and the second feature, thereby making it possible for the first feature and the second feature not to be in direct contact. In addition, the present disclosure may reuse reference numbers and / or letters in various examples. This repetition is for the purpose of brevity and clarity, and does not itself represent the relationship between the various embodiments and / or configurations discussed.

[0018] Furthermore, for ease of description, spatially relative terms, such as "beneath," "below," "lower," "above," and "upper," may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.

[0019] The advanced lithography processes, methods, and materials described below can be used in many applications, including fin-type field effect transistors (FinFETs). For example, fins can be patterned to create relatively tight spacing between features, for which embodiments of the present invention are well suited. Furthermore, the spacers (also known as mandrels) used in forming the fins of FinFETs can be processed according to the following description.

[0020] The overcoat helps prevent particles from contacting the mask surface and negatively impacting the transfer of the mask pattern to the wafer. Particles on the mask surface scatter incident light, which can cause pattern variations and increase the risk that the pattern on the wafer will not meet critical dimension requirements, such as feature size and feature pitch.

[0021] In certain methods of maintaining a pellicle on the mask during the photolithography process, the intensity of light passing through the thin film of the pellicle is reduced. The reason for the reduced intensity is that the light is absorbed and scattered by the thin film. In methods using a reflective mask to transfer the pattern to the wafer, the light will pass through the thin film twice, which doubles the effect of reducing the intensity of the light. The reduction in the intensity of the light incident on the wafer increases the residence time of the light on the wafer to effectively transfer the pattern to the wafer. The residence time is the duration of time that the light is incident on the wafer. The reason for the increase in residence time is that the amount of photon energy used to effectively transfer the pattern to the wafer remains unchanged, but the amount of photon energy of the light passing through the thin film is reduced as described above. The increased residence time, in turn, reduces production throughput and production capacity.

[0022] In some methods of removing the pellicle from the mask before the photolithography process, a cleaning process is used to remove residual adhesive from the mask. The adhesive is used to firmly fix the pellicle to the mask when the mask is not in use. However, the residual adhesive remaining on the mask after removing the pellicle increases the risk of light scattering due to the presence of the residual adhesive, which has a negative impact on the accuracy of transferring the mask pattern to the wafer. The cleaning process has the risk of damaging the pattern of the mask. The risk of damaging the mask increases with the number of cleaning processes performed on the mask. Therefore, repeated application and removal of the pellicle increases the risk of damaging the mask. Damage to the pattern of the mask will have a negative impact on the accuracy of the desired pattern being transferred to the wafer. In some cases, the risk of damage is significant for extreme ultraviolet (EUV) lithography because silicon-based films absorb EUV radiation.

[0023] Additionally, when the mask surface is exposed to the ambient environment, carbon growth on the mask surface increases the risk of altering the pattern on the mask. Carbon growth is the result of a reaction between the mask material and the ambient environment. For example, a ruthenium capping layer, such as that used in EUV lithography, reacts with carbon dioxide in the ambient environment to cause carbon growth on the ruthenium mask. In certain technology nodes (e.g., N10), carbon growth on the mask can increase the critical dimension (CD) of the mask pattern to a point where the pattern cannot be reliably transferred to the wafer. Using an adhesive to attach the pellicle to the mask prevents the ambient environment from reaching the mask surface. Certain embodiments of the present disclosure include the ability to use an inert gas environment between the pellicle and the mask to reduce or prevent carbon growth on the mask surface.

[0024] Figure 1 FIG2 is a schematic diagram of a lithography machine 100 according to certain embodiments. The lithography machine 100 includes a light source 110. The light source 110 is configured to emit electromagnetic radiation for patterning a wafer 120. A mask 130 is disposed in an optical path between the light source 110 and the wafer 120. An optical assembly 140 transfers light from the light source 110 to the mask 130 and then to the wafer 120.

[0025] The light source 110 generates electromagnetic radiation at a wavelength used to pattern the photoresist on the wafer 120. In some embodiments, the light source 110 is an extreme ultraviolet (EUV) light source, a deep ultraviolet (DUV) light source, a vacuum UV (VUV) light source, or other suitable light source. In some embodiments, the light source 110 is a laser, a diode, or other suitable light generating element. In some embodiments, the light source 110 includes a collector for directing the electromagnetic radiation into a common direction along an optical path. In some embodiments, the light source 110 includes a collimator for directing all beams of electromagnetic radiation into parallel directions.

[0026] Wafer 120 includes a substrate (e.g., a semiconductor substrate) having a photoresist layer thereon. The material of the photoresist matches the wavelength of the electromagnetic radiation emitted by light source 110. In some embodiments, the photoresist is a positive photoresist. In some embodiments, the photoresist is a negative photoresist. In some embodiments, wafer 120 includes active components. In some embodiments, wafer 120 includes interconnect structures.

[0027] Mask 130 includes a pattern to be transferred to wafer 120. Mask 130 is free of residual adhesive. Mask 130 is configured to directly receive incident light without passing through a pellicle. Mask 130 also has minimal or no carbon growth. Mask 130 is a reflective mask for reflecting incident light. In some embodiments, mask 130 is a transmissive mask for transmitting incident light.

[0028] Optical components 140 are used to transfer light from light source 110 to mask 130 and from mask 130 to wafer 120. Optical components 140 reduce the size of the pattern on mask 130 so that the size of the pattern formed on wafer 120 is smaller than the size of the pattern on mask 130. In some embodiments, the ratio of the size of the pattern on mask 130 to the size of the pattern on wafer 120 is 2:1, 4:1, 5:1, or other suitable reduction ratios. Optical components 140 are reflective elements and photolithography apparatus 100 is a catoptric arrangement. In some embodiments, at least one of optical components 140 is a transmissive element and photolithography apparatus 100 is a catadioptric arrangement.

[0029] By reducing or avoiding residual adhesive on the mask 130, the accuracy of pattern transfer from the mask 130 to the wafer 120 is improved. Furthermore, minimal or no carbon growth on the mask 130 also helps improve pattern transfer accuracy. Avoiding a cleaning process to remove carbon growth and / or residual adhesive helps increase the useful life of the mask 130 and improve the profitability of manufacturing processes using the lithography machine 100.

[0030] Figure 2A FIG. 2 is a cross-sectional view 200 of a pellicle 220 separated from a mask 210 according to some embodiments. The mask 210 may be used, for example, to perform a lithography operation using a photolithography machine 100 ( Figure 1 ) to transfer the pattern to the wafer. The pellicle 220 is separated from the mask 210 by a separation height H. The pellicle 220 includes a thin film 222 extending across a frame 224. A check valve 226 is disposed in the frame 224. A gasket 230 is disposed in a recess 228 in the frame 224.

[0031] The mask 210 includes a pattern on its surface. The pattern includes a plurality of opaque portions defining reflective portions or transmissive portions. The reflective portion or transmissive portion determines which portion of light incident on the mask 210 is transferred to the wafer (e.g., wafer 120 ( Figure 1 )). The mask 210 extends beyond the edge of the protective film 220. In some embodiments, a carrier (not shown) is attached to the mask 210 to facilitate handling of the mask 210.

[0032] The protective film 220 is used to protect the pattern on the mask 210 by preventing foreign particles from adhering to the mask 210. The film 222 is a transparent layer that extends across the frame 224. In some embodiments, the film 222 is opaque. In some embodiments, the film 222 includes nitrocellulose, fluororesin, quartz, plastic resin, or other suitable materials. In some embodiments, the film 222 is a silicon-based film, for example, including a film composed of a stack of silicon nitride / polycrystalline silicon / silicon nitride / silicon carbide; a film composed of a stack of silicon nitride / p-doped silicon / silicon nitride / ruthenium; or a film composed of a stack of silicon carbide / silicon nitride. In some embodiments, the thickness of the film 222 is in the range of about 2 micrometers (μm) to about 7 μm. As the thickness of the film 222 increases, the risk of the film breaking decreases; however, the weight of the film 222 increases. The thickness of the thin film 222 is sufficient to provide sufficient mechanical strength to withstand the vacuum in the region between the pellicle 220 and the mask 210 (e.g., during EUV lithography). In some embodiments (e.g., in EUV lithography), the thickness of the thin film 222 is between approximately 10 nanometers (nm) and approximately 100 nm. Increasing the thickness of the thin film 222 reduces the risk of cracking, but increases EUV absorption, resulting in reduced reflectivity.

[0033] The frame 224 is used to maintain the separation between the film 222 and the mask 210. The frame 224 is used to contact the mask 210 at a location surrounding the pattern on the mask 210. The frame 224 extends continuously around the pattern on the mask 210 to help ensure that the pattern is protected from foreign particles. In some embodiments, the frame 224 is made of plastic, aluminum, or other suitable materials. In some embodiments, the frame 224 is rectangular, circular, or other suitable shape. In some embodiments, the film 222 is attached to the frame 224 using an adhesive.

[0034] The check valve 226 is used to control the flow of gas between the ambient environment outside the pellicle 220 and the area within the pellicle (i.e., between the pellicle and the mask 210). The check valve 226 is configured to inhibit the flow of gas from the ambient environment into the area within the pellicle 220. In some embodiments, the check valve 226 is a ball check valve, a lift check valve, or another suitable type of check valve. In some embodiments, the check valve 226 comprises plastic, aluminum, or another suitable material. In some embodiments, the material of the check valve 226 is the same as the material of the frame 224. In some embodiments, the material of the check valve 226 is a different material from the material of the frame 224.

[0035] The frame 224 includes a single check valve 226. In some embodiments, multiple check valves 226 are present in the frame 224 to provide redundant control of the flow of gas between the ambient environment and the region within the pellicle 220. For example, if one check valve 226 becomes defective, another check valve 226 can be used to remove gas from between the mask 210 and the pellicle 220 and / or allow gas to enter between the pellicle and the mask.

[0036] The groove 228 extends continuously along the bottom surface of the frame 224. The groove 228 is centered in the bottom surface of the frame 224. In some embodiments, the groove 228 is offset from the center of the bottom surface of the frame 224. The groove 228 has a rectangular shape. In some embodiments, the groove 228 has a triangular, circular, or other suitable shape.

[0037] The depth of the groove 228 is sufficient to partially accommodate the gasket 230 therein. In some embodiments, the depth of the groove 228 is equal to the thickness of the gasket 230 in its relaxed state. In some embodiments, the depth of the groove 228 is less than the thickness of the gasket 230 in its relaxed state. The relaxed state of the gasket 230 is when no force other than the weight of the pellicle 220 is applied to the gasket 230. The depth of the groove 228 relative to the thickness of the gasket 230 in its relaxed state determines the separation height H between the bottom surface of the frame 224 and the mask 210. In some embodiments, the separation height H ranges from approximately 2 μm to approximately 50 μm. As the separation height H increases, a stronger vacuum can be generated in the region between the mask 210 and the pellicle 220. This stronger vacuum removes more gas from the region between the mask 210 and the pellicle 220, reducing the risk of carbon growth; however, the risk of damage or deformation of the mask 210 also increases. In some cases, if the separation height H is too small, the vacuum that may be formed between the mask 210 and the pellicle 220 does not have sufficient pressure to hold the pellicle 220 in place during storage.

[0038] The gasket 230 is an elastic material used to help seal the area between the pellicle 220 and the mask 210 from the surrounding environment. The gasket 230 extends continuously around the pattern in the mask 210 and fits within the groove 228. In some embodiments, the gasket 230 is secured to the frame 224 using an adhesive or other suitable securing means. In some embodiments, the gasket 230 is detachable from the frame 224. The gasket 230 has a circular cross-section. In some embodiments, the gasket 230 has a rectangular cross-section, a triangular cross-section, or another suitable shape. In some embodiments, the gasket 230 comprises rubber, resin, or another suitable material.

[0039] When a vacuum is applied to the area between the pellicle 220 and the mask 210, the gasket 230 deforms to create an airtight seal that prevents the passage of gas. In some embodiments, a portion of the gasket 230 extends between the frame 224 and the mask 210 to prevent the frame 224 from directly contacting the mask 210. In some embodiments, when a vacuum is applied to the area between the pellicle 220 and the mask 210, the gasket 230 fits completely within the groove 228 and the frame 224 directly contacts the mask 210.

[0040] In some embodiments, before applying vacuum, an inert gas is used to purge the area between the pellicle 220 and the mask 210. In some embodiments, the inert gas includes nitrogen, a halogen gas, or other suitable inert gas. Purging with an inert gas helps further reduce the interaction between the mask and the surrounding atmosphere, thereby further reducing the risk of carbon growth on the mask 210.

[0041] In some embodiments, the bottom surface 229 of the frame 224 includes a micro-suction cup ( Figure 5 ) or electrostatic sticker ( Figure 4 Including micro-suction cups or electrostatic stickers on the bottom surface 229 helps prevent the ambient environment from reaching the inside of the pellicle 220. In some embodiments, when the bottom surface 229 includes micro-suction cups or electrostatic stickers, the magnitude of the negative pressure generated by the vacuum obtained through the check valve 226 is reduced because the additional protection provided by the micro-suction cups or electrostatic stickers can provide sufficient protection for the mask 210 with the reduced pressure.

[0042] Figure 2B FIG2 is a cross-sectional view 200′ of pellicle 220 in contact with mask 210 according to certain embodiments. Compared to cross-sectional view 200, cross-sectional view 200′ shows the configuration of pellicle 220 when a vacuum is applied to the area between pellicle 220 and mask 210. The vacuum causes pressure from the surrounding environment to depress pellicle 220 and deform gasket 230 to form an airtight seal with mask 210.

[0043] The flow of gas is controlled based on the check valve 226. As shown by the arrow between the cross-sectional view 200 and the cross-sectional view 200', the pellicle 220 can be transformed from the configuration in the cross-sectional view 200 to the configuration in the cross-sectional view 200' without damaging the structure of the pellicle 220. The ability to repeatedly securely attach the pellicle 220 to the mask 210 and remove the pellicle 220 from the mask 210 helps increase the useful life of the mask 210 and helps ensure accurate pattern transfer from the mask 210 to the wafer.

[0044] Removing gas from the area between pellicle 220 and mask 210 to create a vacuum reduces the risk of carbon growth on the surface of mask 210. This reduced risk of carbon growth helps ensure that the pattern of mask 210 does not change over time. Furthermore, using a vacuum to securely attach pellicle 220 to mask 210 and remove pellicle 220 eliminates the need for adhesive on mask 210. By eliminating the use of adhesive on mask 210, one or more cleaning processes to remove residual adhesive are also avoided, thereby reducing the risk of damage to the pattern of mask 210 during the cleaning process.

[0045] In some embodiments, the bottom surface 229 of the frame 224 includes a micro suction cup ( Figure 5 ) or static stickers ( Figure 4 ), a positive pressure is used to remove the pellicle 220 from the mask 210. In some embodiments, the positive pressure is generated by introducing an inert gas through the check valve 226.

[0046] Figure 3A FIG is a cross-sectional view of a check valve 300 of a diaphragm in a configuration that allows gas flow according to certain embodiments. The check valve 300 is a portion of a diaphragm, such as the check valve 226 ( Figure 2A). The check valve 300 is an example of a ball check valve; however, one of ordinary skill in the art will understand that other types of check valves may be used. The check valve 300 includes an opening 310 connected to the interior of the diaphragm. A port 320 connects the opening 310 to the interior of the check valve 300. A ball 330 is movably positioned within the check valve 300. In the check valve 300, the ball 330 is positioned to allow gas to flow through the port 320. The position of the ball 330 is determined by the pressure difference between the opening 310 and the interior of the check valve 300. In some embodiments, the ball 330 is biased against the port 320 by a spring or other type of biasing element. In some embodiments, the check valve 300 includes an element for mechanically displacing the ball 330 within the check valve 300. For example, in some embodiments, an operator may manipulate a protrusion or other suitable tool to hold ball 330 in place to allow flow from the interior of check valve 300 into the interior of the pellicle via port 320. The ability to hold the ball in place to allow flow into the interior of the pellicle would allow for purging the interior of the pellicle with an inert gas or to aid in removing the pellicle from the mask by generating positive pressure within the pellicle.

[0047] Figure 3B is a cross-sectional view of a check valve 300' for overfilm in a configuration that blocks gas flow, according to certain embodiments. The check valve 300' includes the same structure as the check valve 300, and for the sake of clarity, identical elements are no longer labeled. Compared to the check valve 300, the check valve 300' includes a ball 330 positioned to prevent gas from passing through the port 320. The higher pressure within the interior of the check valve 300' forces the ball 330 against the port 320 to block gas from passing through the port 320. In this way, the check valve 300' can help prevent gas from the ambient environment from reaching the pattern of the mask during storage of the mask. Reducing the degree of exposure to ambient gas helps reduce or prevent carbon growth on the mask to extend the useful life of the mask.

[0048] Figure 4 FIG. 4 is a cross-sectional view 400 of a pellicle 420 securely attached to a mask 410 according to certain embodiments. The mask 410 is equivalent to the mask 210 ( Figure 2A Protective film 420 is similar to protective film 220. Film 422 is equivalent to film 222. Compared to protective film 220, protective film 420 includes electrostatic stickers 440 between frame 424 and mask 410. Protective film 420 lacks check valves and grooves in frame 424. Electrostatic stickers 440 are used to securely fix frame 424 to mask 410 in the area surrounding the pattern on mask 410.

[0049] The electrostatic sticker 440 is attached to the frame 424 by an adhesive or by other suitable attachment configurations. The electrostatic sticker 440 includes a plastic film. The plastic film can be bonded to the mask 410 because the bonding force between the material of the plastic film and the mask 410 acts to form a vacuum between the two surfaces. The plastic film acts like a suction cup to hold the film to the mask 410. In certain embodiments, the thickness of the plastic film is in the range of about 0.1 millimeters (mm) to about 1.0 mm. The bonding force between the electrostatic sticker 440 and the mask 410 is smaller than the bonding force when the frame 424 is connected to the mask 410 by an adhesive. However, using electrostatic force instead of an adhesive to hold the protective film 420 to the mask 410 avoids the cleaning process for removing residual adhesive, which increases the service life of the mask 410.

[0050] Figure 5 FIG. 5 is a cross-sectional view 500 of a protective film 520 securely attached to a mask 510 according to certain embodiments. The mask 510 is equivalent to the mask 210 ( Figure 2A Protective film 520 is similar to protective film 220. Film 552 is equivalent to film 222. Compared to protective film 220, protective film 520 includes multiple micro suction cups 550 between frame 524 and mask 510. Protective film 520 lacks check valves and grooves in frame 524. Micro suction cups 550 are used to securely fix frame 524 to mask 510 in the area surrounding the pattern of mask 510.

[0051] Micro suction cups 550 are disposed on the bottom surface of the frame 524. The enlarged portion of the cross-sectional view 500 includes the micro suction cups 550 aligned in a two-dimensional array on the frame 524. In some embodiments, at least one micro suction cup 550 in a row is offset relative to the micro suction cups 550 in an adjacent row. The offset of the micro suction cups 550 relative to each other helps prevent foreign particles from passing between adjacent micro suction cups 550 and contacting the pattern on the mask 510.

[0052] The micro suction cups 550 comprise a flexible material, such as rubber, silicone, vinyl, polyurethane, or other suitable material. In certain embodiments, the diameter of an individual micro suction cup 550 is in the range of about 5 μm to about 200 μm. As the size of the individual micro suction cups increases, the amount of force required to remove the frame 524 from the mask 510 increases. The frame 524 is securely fixed to the mask 510 by applying a downward force on the frame 524. In certain embodiments, the downward force is applied by an operator. In certain embodiments, the downward force is applied by a tool (e.g., a robotic arm or other suitable tool).

[0053] In some embodiments, the micro suction cups 550 are individually fixedly secured to the frame 524. In some embodiments, a plurality of micro suction cups 550 are integrally formed from a single piece of material and fixedly secured to the frame 524 in a group. In some embodiments, more than one group of micro suction cups 550 is attached to the frame 524. The micro suction cups 550 are fixedly secured to the frame 524 by adhesive or other suitable attachment arrangements. Using the micro suction cups 550 rather than adhesive to hold the pellicle 520 to the mask 510 avoids a cleaning process for removing residual adhesive, which increases the useful life of the mask 410.

[0054] Compared with the protective film 220 ( Figure 2A ), protective film 420( Figure 4 ) and protective film 520( Figure 5 ) does not help reduce carbon growth on the corresponding mask because overcoat 420 and overcoat 520 do not include check valves and lack the ability to create a vacuum between them and the corresponding mask. Due to the low adhesion of the electrostatic sticker 440 and the gaps between adjacent micro-suction cups 550, maintaining a vacuum between the overcoat and the corresponding mask becomes difficult. Therefore, in some cases, the increased complexity of overcoat 420 or 520 may not justify the expense of including a check valve. However, compared to other approaches, overcoat 420 and overcoat 520 still protect the corresponding mask from foreign particles during storage and can be removed without leaving residual adhesive, which helps extend the life of the mask.

[0055] Figure 6A FIG. 6 is a cross-sectional view 600 of a process for removing a pellicle 620 according to some embodiments. Mask 610 is similar to mask 210, mask 410, or mask 510. pellicle 620 is similar to pellicle 420 ( Figure 4 ) or protective film 520( Figure 5 Film 622 is similar to film 422 or film 522. For simplicity, the specific bonding structure between frame 624 and mask 610 (e.g., electrostatic sticker 440 or micro suction cup 550) is not shown. In cross-sectional view 600, film 620 is firmly fixed to mask 610. Force 660 is applied to one side of film 620 at an angle α relative to the outer surface of frame 624.

[0056] A force 660 is applied to remove the side of the pellicle 620 from the mask 610. Attempting to pull the pellicle 620 away from the mask 610 in a direction perpendicular to the top surface of the mask 610 increases the risk of damaging the pellicle 620 or the mask 610. To reduce the risk of damaging the pellicle 620 and the mask 610, the force 660 is applied at an angle α. In some embodiments, the angle α is in a range from about 20 degrees to about 80 degrees. As the angle α increases, the amount of force 660 applied in the removal direction (i.e., perpendicular to the top surface of the mask 610) decreases, and a larger amount of force 660 is required to overcome the forces holding the pellicle 620 to the mask 610. As the angle α decreases, the risk of damaging the pellicle 620 or the mask 610 increases.

[0057] In some embodiments, force 660 is applied using a robotic arm or other mechanism controlled by a controller or an operator. In some embodiments, force 660 is applied by an operator. Force 660 is applied at a single location on pellicle 620. In some embodiments, force 660 is applied at multiple locations on pellicle 620. In some embodiments, the force applied at a first location on pellicle 620 has a different angle or magnitude than the force applied at a second location on pellicle 620.

[0058] Figure 6B FIG. 6 is a cross-sectional view 600′ illustrating a process for removing the protective film 620 according to certain embodiments. Figure 6A ), cross-sectional view 600' includes the side of pellicle 620 separated from mask 610 by a separation distance S. The opposite side of pellicle 620 remains in contact with mask 610. In some embodiments, a spacer element is inserted within the separation distance S to help prevent pellicle 620 from reattaching to mask 610 during the removal process. In some embodiments, the separation distance S is in a range from about 2 μm to about 5 μm. As the separation distance S increases, the amount of torque applied to pellicle 620 increases, and the risk of damaging pellicle 620 increases. As the separation distance S decreases, the risk of pellicle 620 reattaching to mask 610 during the removal process increases.

[0059] Figure 6C 600 ′ and 600 ′′ are cross-sectional views of a process for removing the protective film 620 according to certain embodiments. Figure 6B ), the cross-sectional view 600" includes the pellicle 620 completely separated from the mask 610 by lifting the pellicle 620 in a direction perpendicular to the top surface of the mask 610. By first removing one side of the pellicle 620 from the mask 610 before lifting the pellicle 620 in a direction perpendicular to the top surface of the mask 610, the risk of damaging the pellicle 620 and the mask 610 is reduced. In some embodiments, the same force used to apply the force 660 ( Figure 6A) is used to lift the diaphragm 620. In some embodiments, a different mechanical element than the mechanical element used to apply force 660 is used to lift the diaphragm 620.

[0060] After the removal process, the mask 610 is firmly fixed to the lithography machine (eg, lithography machine 100 ( Figure 1 After the photolithography process is completed, the mask 610 is removed from the photolithography machine and the pellicle 620 is reattached to the mask 610 to store the mask 610.

[0061] Figure 7 FIG. 7 is a flow chart of a method 700 for using a pellicle according to some embodiments. In operation 710, the pellicle is securely fixed to the mask. In some embodiments, the pellicle is secured to the mask by creating a vacuum between the pellicle and the mask (e.g., using a check valve 226 ( Figure 2A and Figure 2B )) to securely attach the protective film to the mask. In some embodiments, an electrostatic sticker (e.g., electrostatic sticker 440 ( Figure 4 )) securely fix the pellicle to the mask. In some embodiments, a plurality of micro suction cups (e.g., micro suction cup 550 ( Figure 5 The pellicle is securely secured to the mask. In some embodiments, the pellicle can be securely secured to the mask using a different process that does not leave residual adhesive on the mask when the pellicle is subsequently removed. In some embodiments, the area between the mask and the pellicle is purged with an inert gas before the pellicle is securely secured to the mask.

[0062] In operation 720, the mask, with the pellicle attached, is placed in a storage container. In some embodiments, the storage container is an EUV dual-pod. In some embodiments, the mask (photomask) is placed in the EUV dual-pod, which is stored in a purge rack filled with an inert gas. This purge rack purges the internal environment and helps preserve the mask. In some embodiments, the mask is placed in the dual-pod using a robotic arm, a conveyor, or other suitable transfer element. In some embodiments, an operator places the mask in the storage container. In some embodiments, the internal environment of the storage container is purged at intervals during the storage of the mask. In some embodiments, the interval is determined based on the storage period (i.e., how long the mask has been in the storage container). In some embodiments, the interval is determined based on the occurrence of an event (e.g., the opening of a door to the storage container or other suitable event).

[0063] In operation 730, the mask with the pellicle attached is removed from the reservoir. In some embodiments, a robotic arm, a conveyor belt, or other suitable transfer element is used to remove the mask from the reservoir. In some embodiments, an operator removes the mask from the reservoir. In some embodiments, the same element as the element used to place the mask in the reservoir can be used to remove the mask from the reservoir. In some embodiments, different elements from the elements used to place the mask in the reservoir can be used to remove the mask from the reservoir. In some embodiments, before removing the mask from the reservoir, the reservoir is transferred to a different location within a fab or to a different building.

[0064] In operation 740, the pellicle is separated from the mask. In some embodiments, the pellicle is separated by releasing a vacuum between the pellicle and the mask. In some embodiments, the pellicle is separated by introducing a positive pressure between the mask and the pellicle. In some embodiments, the pellicle is separated by applying a force to one side of the pellicle to separate the side of the pellicle from the mask and then lifting the pellicle from the mask (e.g., as in Figure 6A 、 Figure 6B ,and Figure 6C In some embodiments, the pellicle is separated from the mask in a controlled environment. In some embodiments, the pellicle is separated from the mask in an uncontrolled environment (e.g., air).

[0065] In operation 750, the mask without the pellicle is mounted in a scanner. The scanner is a photolithography machine (e.g., photolithography machine 100 ( Figure 1 )). The pressure inside the scanner is lower than the pressure outside the scanner, which helps reduce the rate of carbon growth on the mask. In some embodiments, a robotic arm is used to install the mask in the scanner. In some embodiments, an operator installs the mask in the scanner. In some embodiments, the mask can be installed in the scanner using the same elements used to remove the mask from the reservoir and place it in the reservoir. In some embodiments, the mask can be installed in the scanner using different elements than those used to remove the mask from the reservoir and place it in the reservoir.

[0066] In operation 760, a photolithography process is performed using the mask. During the photolithography process, the pattern on the mask is transferred to the wafer. In some embodiments, the photolithography process uses UV light, such as EUV light or VUV light. The dwell time of the photolithography process is shorter than other methods that maintain a pellicle on the mask during the photolithography process. In some embodiments, the photolithography process is repeated multiple times using the same mask without removing the mask from the scanner.

[0067] In operation 770, the mask is removed from the scanner. After the mask is removed from the scanner, the overcoat is reapplied to the mask in operation 710. In some embodiments, a robotic arm is used to remove the mask from the scanner. In some embodiments, an operator removes the mask from the scanner. In some embodiments, the mask can be removed from the scanner using the same elements used to install the mask in the scanner, remove the mask from the reservoir, and place the mask in the reservoir. In some embodiments, the mask can be removed from the scanner using different elements than those used to install the mask in the scanner, remove the mask from the reservoir, or place the mask in the reservoir.

[0068] Compared to other approaches, method 700 provides improved throughput due to reduced dwell time during the photolithography process. Method 700 also helps extend the useful life of the mask by eliminating the need for a cleaning process to remove residual adhesive. In certain embodiments, method 700 facilitates processing at technology nodes equal to or less than N10 by reducing or eliminating carbon growth on the mask by storing the mask under vacuum between the mask and the pellicle.

[0069] In some embodiments, method 700 includes other operations, such as purging the mask with an inert gas before operation 710. In some embodiments, the order of the operations of method 700 may be adjusted, such as applying the pellicle to the mask after it is in the storage container. In some embodiments, at least one operation of method 700 may be omitted. For example, in some embodiments, if the mask is not stored before use in the scanner, operation 720 is omitted.

[0070] The above description provides several embodiments for securely securing a pellicle to a mask to protect the mask from foreign particles that adhere to the mask. The pellicle can be removed from the mask without leaving adhesive residue on the mask. Avoiding adhesive residue on the mask helps extend the useful life of the mask by requiring the mask to undergo fewer, if any, cleaning processes. In certain embodiments, a vacuum is used to securely secure the pellicle to the mask, which helps reduce the risk of carbon growth on the mask. This reduction in carbon growth allows the use of masks with technology nodes equal to or less than N10.

[0071] One aspect of the present disclosure relates to a diaphragm. The diaphragm includes a frame, a film, and a gasket. The frame includes a check valve configured to allow gas to flow from an interior of the diaphragm to an exterior of the diaphragm, and a bottom surface of the frame defines a groove. The film extends across the frame. The gasket is configured to fit within the groove.

[0072] In certain embodiments, the check valve comprises a ball check valve.

[0073] In some embodiments, the spacer is fixed to the frame.

[0074] In certain embodiments, the frame includes a plurality of the check valves.

[0075] In some embodiments, the depth of the groove is less than or equal to the thickness of the gasket.

[0076] Another aspect of the present disclosure relates to a method for using a pellicle. The method includes the steps of: securely attaching the pellicle to a mask, wherein the pellicle extends around a pattern on the mask; separating the pellicle from the mask; installing the mask in a scanner, wherein installing the mask in the scanner includes installing the mask in the scanner without performing a cleaning process on the mask; and performing a photolithography process using the scanner to transfer the pattern on the mask to a wafer.

[0077] In some embodiments, the step of securely securing the pellicle to the mask includes securely securing the pellicle to the mask using an electrostatic sticker.

[0078] In some embodiments, the step of firmly fixing the pellicle to the mask includes firmly fixing the pellicle to the mask using a micro suction cup.

[0079] In some embodiments, the step of securely securing the pellicle to the mask includes forming a vacuum between the pellicle and the mask.

[0080] In some embodiments, the method further includes: purging a region between the mask and the pellicle using an inert gas before forming the vacuum.

[0081] In some embodiments, the method further comprises maintaining the vacuum between the pellicle and the mask using a check valve.

[0082] In some embodiments, separating the pellicle from the mask includes releasing the vacuum between the pellicle and the mask.

[0083] In some embodiments, separating the pellicle from the mask includes applying a force to a first side of the pellicle at an angle relative to a frame of the pellicle.

[0084] In some embodiments, the method further includes maintaining a second side of the pellicle in contact with the mask while separating the first side of the pellicle from the mask using the applied force, wherein the second side is opposite the first side.

[0085] In some embodiments, the method further includes lifting the pellicle in a direction perpendicular to a top surface of the mask to separate the second side of the pellicle from the mask.

[0086] Yet another aspect of the present disclosure relates to a method for using a pellicle. The method includes the steps of: securely securing the pellicle to a mask, wherein the pellicle extends around a pattern on the mask, and securely securing the pellicle to the mask includes securely securing the pellicle to the mask without using an adhesive; detaching the pellicle from the mask; installing the mask in a scanner; and performing a photolithography process using the scanner to transfer the pattern on the mask to a wafer.

[0087] In some embodiments, the step of firmly fixing the pellicle to the mask includes firmly fixing the pellicle to the mask using an electrostatic sticker or a micro suction cup.

[0088] In some embodiments, the step of securely securing the pellicle to the mask includes forming a vacuum between the pellicle and the mask.

[0089] In some embodiments, separating the pellicle from the mask includes releasing the vacuum between the mask and the pellicle.

[0090] In some embodiments, the method further includes purging a region between the mask and the pellicle with an inert gas before forming the vacuum.

[0091] The features of several embodiments are summarized above so that those skilled in the art can better understand the various aspects of the embodiments of the present invention. Those skilled in the art will appreciate that they can readily use the embodiments of the present invention as a basis for designing or modifying other processes and structures to implement the same purposes and / or achieve the same advantages as the embodiments described herein. Those skilled in the art will also recognize that these equivalent constructions do not depart from the spirit and scope of the embodiments of the present invention, and that they can make various changes, substitutions, and modifications thereto without departing from the spirit and scope of the embodiments of the present invention.

Claims

1. A protective film, characterized in that: include: A framework, wherein the framework comprises: an exterior surface and an interior surface, wherein the interior surface defines an interior of the pellicle: a check valve extending from the exterior surface to the interior surface, wherein the check valve is configured to allow gas to flow from the interior of the diaphragm to the exterior of the diaphragm; and The bottom surface of the frame defines only a single recess; a membrane extending across the frame; and A gasket is configured to fit within the single groove.

2. The protective film according to claim 1, characterized in that The check valve comprises a check ball valve.

3. The protective film according to claim 1, characterized in that A first distance between a bottom surface of the check valve within the frame and a bottom surface of the gasket is greater than a second distance between the bottom surface of the frame and the bottom surface of the gasket.

4. The protective film according to claim 1, characterized in that The frame includes a plurality of the check valves.

5. The protective film according to claim 1, characterized in that The depth of the single groove is less than or equal to the thickness of the gasket.

6. The protective film according to claim 1, characterized in that The film is transparent, and the thickness of the film is between 10 nanometers and 7 micrometers.

7. A protective film, characterized in that: include: A framework, wherein the framework comprises: an exterior surface and an interior surface, wherein the interior surface defines an interior of the pellicle: a membrane extending across the frame; as well as A plurality of micro suction cups are arranged in an array on the bottom surface of the frame, and a micro suction cup in a row of the array of the plurality of micro suction cups is offset relative to a corresponding micro suction cup in an adjacent row.

8. The protective film according to claim 7, characterized in that The materials of the plurality of micro suction cups include rubber, silicone, vinyl or polyurethane.

9. The protective film according to claim 7, characterized in that Also included is a check valve extending from the exterior surface to the interior surface, wherein the check valve is configured to allow gas to flow from the interior of the diaphragm to the exterior of the diaphragm, and the check valve comprises a ball check valve.

10. The protective film according to claim 9, characterized in that The frame includes a plurality of the check valves.

11. The protective film according to claim 7, characterized in that A diameter of one of the plurality of micro suction cups ranges from 5 μm to 200 μm.

12. A method of using a cuticle, the method comprising: The method further comprises: fixing the pellicle to the mask, wherein the pellicle comprises a frame extending around the pattern on the mask and a film extending across the frame, and fixing the pellicle to the mask comprises: creating a vacuum between the pellicle and the mask using a check valve within the frame; and Sealing the vacuum using only a single gasket within a groove within the frame; releasing the vacuum; separating the pellicle from the mask by directly applying a force to a first side of the pellicle, wherein the first side of the pellicle is separated from the mask before separating the second side of the pellicle from the mask; installing the mask in a scanner, wherein the step of installing the mask in the scanner includes installing the mask in the scanner without performing a cleaning process on the mask; and A photolithography process is performed using the scanner to transfer the pattern on the mask to a wafer.

13. The method for using a cuticle according to claim 12, characterized in that The step of securely securing the pellicle to the mask includes securely securing the pellicle to the mask using the check valve separated from the groove.

14. The method for using a cuticle according to claim 12, wherein The step of securely securing the pellicle to the mask includes using a check ball valve.

15. The method for using a cuticle according to claim 14, characterized in that The method further includes purging a region between the mask and the pellicle using an inert gas before forming the vacuum.

16. The method for using a cuticle according to claim 14, wherein The method further includes maintaining the vacuum between the pellicle and the mask using the check ball valve.

17. The method for using a cuticle according to claim 14, wherein The step of separating the pellicle from the mask includes releasing the vacuum between the pellicle and the mask.

18. The method for using a cuticle according to claim 12, wherein The step of separating the pellicle from the mask includes applying the force to the first side of the pellicle at an angle relative to a frame of the pellicle.

19. The method for using a cuticle according to claim 18, characterized in that The angle is between 20 degrees and 80 degrees.

20. The method for using a cuticle according to claim 19, wherein The method further includes lifting the pellicle in a direction perpendicular to a top surface of the mask to separate the second side of the pellicle from the mask.

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