Pellicle frame and pellicle assembly with the same

Abstract

This invention discloses a protective membrane frame having a pair of frame members. Each of the frame members is shaped to correspond to a support portion of the protective membrane. These frame members are coupled to each other by overlapping their plate surfaces to form a double-layer structure. Recesses are formed in corresponding areas of the opposing inner surfaces of the frame members. These recesses create vents that open laterally from the plate surfaces when the frame members are coupled. A filter is inserted into each vent. This configuration facilitates easy cleaning and inspection of the protective membrane frame and minimizes particle generation during filter material handling. Furthermore, it provides sufficient buffering to protect the membrane from pressure changes within the internal space of the protective membrane frame, thereby preventing damage to the membrane.

Description

[Technical Field]

[0001] The present invention relates to a protective film frame, and more particularly, to a protective film frame for mounting a protective film on the top of a photomask, and to a protective film assembly including the protective film frame. [Previous Technology]

[0002] Extreme ultraviolet (EUV) lithography technology using EUV exposure light with a wavelength of 13.5 nm is being developed to implement fine patterns. In the lithography process, the photomask serves as the mainboard for patterning. When particles or other contaminants adhere to the photomask, the exposure light can be absorbed or reflected by these contaminants, potentially damaging the transferred pattern. Therefore, a protective film is installed above the photomask to prevent contaminants from adhering to the photomask surface. As circuit linewidths continue to decrease, the size of contaminants that affect pattern damage also decreases, making the role of the protective film in photomask protection increasingly important.

[0003] Figure 1 is a diagram showing the protective film assembly, in which the protective film is attached to the frame.

[0004] The protective film assembly 80 includes a protective film 30 and a protective film frame 50.

[0005] The protective film 30 includes a rectangular film 20 that transmits exposure light and a support portion 10 of the support film 20. Typically, the protective film 30 shown in FIG1 is manufactured by forming the film 20 on a silicon substrate and then etching the lower surface of the substrate to form the support portion 10.

[0006] Once the protective film 30, having film 20 and support portion 10, is completed, the protective film frame 50 is attached to the lower surface of the support portion 10. For use in the exposure process, the protective film 30 must be mounted on the photomask P, and as a preparatory step, the protective film frame 50 is attached to the lower surface of the support portion 10. Adhesive is applied to the upper surface of the protective film frame 50 to bond the support portion 10 and the protective film frame 50. With the support portion 10 of the protective film 30 attached to the upper surface of the protective film frame 50, the protective film assembly 80 is completed.

[0007] When the protective film assembly 80 is adhered to the photomask P, the protective film 30 is mounted on the photomask. In order to adhere the protective film assembly 80 to the photomask P, an adhesive is applied to the lower surface of the protective film frame 50.

[0008] The protective film assembly 80, mounted on the photomask P, is then used within the exposure apparatus. During the exposure process, the interior of the exposure apparatus is maintained under vacuum, and air is vented from the apparatus to the outside before exposure. Due to this venting pressure, air is evacuated from the internal space S of the protective film assembly 80, more precisely, from the space formed by the protective film 30, the protective film frame 50, and the photomask P, thereby generating pressure on the protective film 30. This can lead to damage to the counter film 20. To prevent this, the protective film frame 50 is provided with vent holes.

[0009] Figure 2 is an enlarged cross-sectional view of Figure 1, showing the detailed structure of the protective membrane frame 50. The protective membrane frame 50 has a columnar cross-section and a rectangular frame shape that opens vertically in a plane.

[0010] The protective membrane frame 50 includes vent holes 52 formed to penetrate the sidewalls and horizontally spaced at intervals along the sidewalls. When the protective membrane assembly 80 is mounted on the photomask P, the vent holes 52 allow communication between the internal space S formed between the protective membrane assembly 80 and the photomask P and the external space. During the vacuum suction process of the device, air from the internal space S is discharged to the outside through the vent holes 52, thereby preventing pressure difference between the internal space S and the outside of the protective membrane assembly 80 and thus avoiding damage to the membrane 20.

[0011] Although the vent 52 is used to prevent damage to the membrane 20, it can also pose a risk by allowing particles from the external environment to enter the internal space S. To prevent the ingress of external particles, a filter 56 is installed in the vent 52. The filter 56 is configured as a filter membrane positioned vertically across the vent 52. To install the filter 56, a filter receiving opening 52a is formed in the central portion of each vent 52, vertically penetrating the protective membrane frame 50 to accommodate the upper and lower portions of each filter 56. The filter 56 is then installed by inserting it through the receiving opening 52a in the protective membrane frame 50.

[0012] The air entering the interior space S through the exhaust port 52 is filtered by the filter 56 to prevent external pollutants or particles from seeping into the interior space S.

[0013] However, in the conventional structure, a machining process is required to form vent holes 52 on the side of the protective membrane frame 50 for the installation of the filter 56. For example, a precise drilling process is required to produce the vent holes 52. These processes generate particles, making it necessary to perform precise cleaning after the vent holes 52 are formed to remove the particles from them. However, since the vent holes 52 have a very small diameter and penetrate the relatively thick sidewalls of the protective membrane frame 50, cleaning and detecting residual particles inside the vent holes 52 is challenging.

[0014] Furthermore, in this conventional structure, since the filter 56 needs to cover the exhaust port 52 after installation, it must be processed into a form similar to a wide rectangular membrane with a specific thickness. Therefore, in order to manufacture the filter 56, the filter material in the shape of a rectangular column must be prepared and then cut into thin sheets. This process results in the entire outer surface of the filter 56 being formed by a cut surface created by a cutting tool. Therefore, the outer surface of the filter 56 is covered by particles generated during cutting, meaning that the filter 56 itself, intended to prevent particles, can become a source of particles.

[0015] Furthermore, in conventional protective membrane frames, enhancing the filtration capacity of filter 56 may not adequately protect membrane 20 from pressure changes within the internal space S. For example, improving the filtration efficiency of filter 56 requires a higher filter density, thereby increasing the sealing strength of vent 52. Therefore, if a significant pressure change occurs within the internal space S, the strong blocking force of filter 56 can prevent vent 52 from buffering the pressure change, potentially damaging membrane 20. Conversely, reducing the density of filter 56 during high-pressure changes to increase the buffering effect of vent 52 will weaken the filtration efficiency of filter 56. [Summary of the Invention]

[0016] The present invention has been designed to solve the above problems, and the object of the present invention is to provide a protective film frame that facilitates easy cleaning and inspection.

[0017] Another object of the present invention is to provide a protective membrane frame that can minimize particle generation during the filter manufacturing process.

[0018] Another objective of the present invention is to provide a protective membrane frame that provides sufficient buffering to protect the membrane from pressure changes within the internal space of the protective membrane frame, while enhancing filtration efficiency.

[0019] To achieve the above objective, the present invention provides a protective film frame for mounting a protective film on a photomask by attaching the protective film to the photomask. The protective film includes a film for transmitting exposure light and a support portion for supporting the outermost edge region of the film. The protective film frame includes: a pair of frame members, each formed to match the shape of one of the support portions, coupled and overlapping each other by their plate surfaces to create a double-layer structure, and each of the frame members having a recessed portion formed in a corresponding area on a relatively inner surface, the recessed portion forming an exhaust hole that opens laterally from the plate surfaces in the coupled state; and a filter disposed in the exhaust hole between the pair of frame members to block the exhaust hole.

[0020] A plurality of such recesses are formed on each of the frame members to form a plurality of such vent holes.

[0021] Preferably, the height of the filter in its cross-section is greater than the height of the vent hole.

[0022] A receiving groove is formed on the bottom surface of one of the recessed portions to accommodate the filter in contact with a portion of the bottom surface.

[0023] The storage recess is formed along one of the longitudinal directions of the bottom surface.

[0024] One of the cross sections of the storage recess has a partially arc shape, and the filter is formed to have a circular cross section.

[0025] Alternatively, one of the cross sections of the receiving groove has a partial polygonal shape, and the filter is formed to have a cross section with a polygonal shape.

[0026] The filter preferably has a tubular shape.

[0027] The filter preferably has a plurality of pores.

[0028] The length of the storage groove along one of the longitudinal directions is greater than the length of one of the recessed portions.

[0029] The sections extending beyond the recessed portion at both ends of the receiving groove are formed with a cross-section having a semi-circular shape or a polygonal shape.

[0030] An adhesive may be applied to at least a portion of the receiving recess to provide adhesion to the filter.

[0031] At least one of the frame members has a pinhole on one side, the pinhole being formed to provide for securing one area of ​​the protective membrane frame from an external pin.

[0032] Each of these frame members has a joint portion formed to be assembled with each other by mutual cooperation.

[0033] The joint portion includes a pair of protrusions formed on one inner surface of one of the frame members and a recess formed on one inner surface of the other of the frame members, the recess having a shape corresponding to the protrusions.

[0034] The joint portion is formed between the plurality of such vent holes.

[0035] According to another aspect of the present invention, a protective film assembly is provided, comprising a protective film frame having the structure described above and a protective film attached to the protective film frame.

[0036] According to the present invention, the protective membrane frame is formed by coupling two vertically arranged frame members and generating vent holes between the combined members, thereby enabling easy cleaning and detection of particles.

[0037] Furthermore, by manufacturing the filter by cutting the tubular filter material to a specified length in the longitudinal direction, the cut surface area is minimized to reduce particle generation during the cutting process. In addition, the cut surface is not placed inside the exhaust port, thus preventing particles from entering the internal space of the protective membrane assembly.

[0038] Furthermore, in this invention, the filter is manufactured in a tubular shape and positioned along the longitudinal direction of the plate surface of the protective membrane frame, thereby allowing a single filter to provide double-layer shielding for the exhaust port. Therefore, even with a low filter density, sufficient filtration can be achieved through dual filtration. In addition, if there is a sudden pressure change between the inside and outside of the protective membrane frame, the space between the two filters buffers the pressure change, thereby preventing damage to the membrane.

Implementation Method

[0040] The present invention will be described in detail with reference to the accompanying drawings. For the sake of brevity, the general structure of the protective film assembly is omitted, as it has been described with reference to Figures 1 and 2. The same element symbols are used to indicate the elements shown in Figures 1 and 2 that are related to the protective film in this specification.

[0041] FIG3 is an exploded perspective view of the protective film frame according to the present invention, and FIG4 is a side view of FIG3 in the assembled state. Similar to the prior art described above, the protective film frame 300 is mounted on top of the photomask P after the protective film 30 is attached. The protective film 30 includes a rectangular film 20 for transmitting exposure light and a support portion 10 at the outer edge of the support film 20.

[0042] The protective film frame 300 of the present invention includes a pair of frame members 100 and 200, specifically a first frame member 100 and a second frame member 200, and a filter 400.

[0043] Each of the first frame member 100 and the second frame member 200 is formed into a rectangular frame shape corresponding to the support portion 10 of the protective film 30. This rectangular frame shape refers to an overall rectangular plate form in which only the edge area remains and the rest is removed. Except for the area of ​​the film 20 forming the support portion 10, the removed area corresponds to the window area through which EUV exposure light passes. Therefore, each frame member 100, 200 has a structure in which four elongated rods form a rectangular frame. Each frame member 100, 200 is manufactured as a single body via a single molding process.

[0044] The first frame member 100 and the second frame member 200 are coupled to each other by overlapping their plate surfaces to form a double-layer structure. Specifically, the first frame member 100 is positioned at the bottom and the second frame member 200 is positioned at the top, and the first frame member and the second frame member are vertically coupled. The filter 400 is disposed between the two frame members 100 and 200.

[0045] Figures 5 and 6 show the first frame member 100 in Figure 3, while Figures 7 and 8 show the second frame member 200. To make the construction of the second frame member 200 clear, Figures 7 and 8 depict an inverted state from the state in Figure 3.

[0046] Each frame member 100, 200 has a recessed portion 110 formed in a corresponding region on its inner surface (i.e., the upper surface of the first frame member 100 and the lower surface of the second frame member 200). When the two frame members 100 and 200 are coupled, the opposing recessed portions 110 form vent holes 330, which open laterally from the plate surface of the protective membrane frame 300. A filter 400 is inserted into this vent hole 330 to block the vent hole. A plurality of recessed portions 110 on each frame member 100, 200 form a plurality of vent holes 330.

[0047] Each recessed portion 110 is formed in a specific region along the longitudinal direction of each individual frame member 100, 200 in a shape that is recessed from the plate surface to a uniform depth. In addition, each recessed portion 110 spans the entire width of the plate surface of the frame member 100, 200.

[0048] The bottom surface of each recessed portion 110 includes a receiving groove 120 that is further recessed from the recessed portion 110. This receiving groove 120 is formed along the longitudinal direction of the bottom surface of the recessed portion 110, wherein two ends 122 extend outward beyond the recessed portion 110.

[0049] The receiving groove 120 is shaped to correspond to the external shape of the filter 400, specifically having a partially arcuate cross-section. However, the shape is not limited to that shape and may vary depending on the shape of the filter 400. The filter 400 may have a polygonal cross-section, such as a rectangular cross-section.

[0050] The filter 400 is positioned along the length of the recess 110, wherein its cross-section is formed in a circular shape, or more specifically, a tubular shape. However, the filter 400 is not limited to a tubular shape and may have a polygonal or circular shape with a plurality of holes. The portion of the filter 400 that contacts the bottom surface of the recess 110 is received within a receiving groove 120. The receiving groove 120 stably maintains the filter 400 in a fixed position within the vent 330. To further enhance the fixing strength of the filter 400, an adhesive may be applied within the receiving groove 120 to provide adhesion to the filter 400. The adhesive may be applied to the entire length of the receiving groove 120 or only to a specific section. For example, the adhesive may be applied only to the end 122 of the receiving groove 120 outside the recess 110.

[0051] Figure 9 is a partial enlarged view of Figure 6, and Figure 10 shows the state in which the filter 400 is installed in Figure 9.

[0052] As described above, the receiving groove 120 is longer in its longitudinal direction than the recessed portion 110 itself. Specifically, the receiving groove 120 is recessed from the bottom surface of the recessed portion 110, wherein its end 122 extends beyond the section of the recessed portion 110 and is recessed directly from the plate surface of each frame member 100, 200. The extended end 122 of the receiving groove 120 beyond the recessed portion 110 is semi-circular in shape to accommodate the tubular filter 400.

[0053] Utilizing this structure, as shown in Figure 10, almost all of the filter 400 is positioned within the recessed portion 110, with the remaining portions of each end of the filter 400 extending into the semi-circular ends 122 of the receiving grooves 120. The filter 400 is configured such that its height in cross-section is greater than the height of the vent 330. Therefore, the top and bottom portions of the filter 400 are respectively received within the upper and lower receiving grooves 120, thus fixing the position of the filter 400 within the recessed portion 110. When the two frame members 100 and 200 are coupled, the filter 400 remains inserted into the vent 330, thereby shielding the vent, while the ends of the filter 400 are pressed and fixed by the coupling of the ends 122 of the two receiving grooves 120.

[0054] If the filter 400 has a polygonal cross-section, the end 122 of the receiving groove 120 is shaped to correspond to the polygonal shape, thus accommodating half of the cross-section of the filter.

[0055] Each frame member 100, 200 includes a joint portion 150, 250 formed for assembly by mutual engagement. Specifically, as shown in Figures 7 and 8, the second frame member 200 includes a protrusion 250 projecting from its inner surface, and the inner surface of the first frame member 100 includes a recess 150 corresponding to the protrusion 250, thereby forming the joint portions 150, 250. These joint portions 150, 250 couple the first frame member 100 and the second frame member 200.

[0056] In an embodiment of the present invention, eight joining portions 150, 250 are formed at the four corners and four edges of the protective film frame 300. The number of joining portions 150, 250 can be adjusted as needed. The joining portions 150, 250 at the corners are generally "L"-shaped to match the curved surface of the corner. The joining portions 150, 250 can be configured in different ways, as long as they can be detachably coupled by mutual engagement. The joining portions 150, 250 are positioned between the vent holes 330, thus alternating with the vent holes 330 along the plate surface of the protective film frame 300.

[0057] The sides of the frame members 100 and 200 include pinholes 180 that provide clamping areas for external devices to hold the protective film frame 300 with a needle. The external device can clamp the protective film frame 300 for purposes such as moving it to a storage location or mounting it onto the photomask P. The pinholes 180 are formed at at least two locations on the protective film frame 300, such as two opposite locations, thereby allowing the external device to insert a needle at multiple points to hook onto the protective film frame 300.

[0058] Figure 11 is an enlarged perspective view of the filter 400 shown in Figure 10. The filter 400 of the present invention has an overall tubular shape. The material of the filter 400 can be appropriately selected as needed, preferably a material having multiple pores.

[0059] Figure 12 shows the filter material used to manufacture the filter in Figure 10. An extremely long tubular filter material 400a is prepared, and each filter 400 can be obtained by cutting the filter material 400a to a predetermined length in the direction of the arrow, as shown in Figure 11. By cutting the tubular filter material 400a, the cut surface becomes the end of each filter 400. When the filter 400 is installed as shown in Figure 10, the cut surface is positioned in the two ends 122 of the receiving groove 120, and therefore, in the coupled state of the first frame member 100 and the second frame member 200 as shown in Figure 4, the cut surface is not exposed to the external air within the exhaust port 330. Therefore, contaminants from the filter manufacturing process on the cut surface are not considered particles.

[0060] Figure 13 is a cross-sectional view of the vent 330 portion of Figure 4.

[0061] When the filter 400 is positioned between the two frame members 100 and 200, the tubular cross-sectional structure of the filter 400 forms a double-layer structure in the direction of air inflow / outflow through the vent 330. Even if the density of the filter 400, i.e., the sealing strength of the vent 330, decreases, this double filtration effect still allows for adequate filtration. Furthermore, even if a sudden pressure change occurs between the inside and outside of the protective membrane frame 300, the space inside the tube, i.e., the space in the double-layer filter, provides a buffering effect, thereby effectively preventing damage to the membrane 20.

[0062] Although the invention has been described with reference to the accompanying drawings, the structures presented are for illustrative and explanatory purposes only and are not intended to limit the meaning or scope of the invention as defined in the claims. Therefore, those skilled in the art will understand that various modifications and equivalent alternative structures are possible, and the true scope of the invention should be defined by the claims. [Simplified Explanation of the Diagram]

[0039] Figure 1 illustrates the protective membrane assembly, wherein the protective membrane is attached to the frame; Figure 2 is a partial enlarged cross-sectional view of Figure 1; Figure 3 is an exploded perspective view of the protective membrane frame according to the present invention; Figure 4 is a side view of the protective membrane frame in the assembled state from Figure 3; Figure 5 is a top view of the first frame member in Figure 3; Figure 6 is a partial perspective view of Figure 5; Figure 7 is a bottom view of the second frame member in Figure 3; Figure 8 is a partial perspective view of Figure 7; Figure 9 is a partial enlarged view of a portion of Figure 6; Figure 10 illustrates the state in which the filter is installed in Figure 9; Figure 11 is an enlarged perspective view of the filter in Figure 10; Figure 12 shows the filter material used to manufacture the filter in Figure 10; and Figure 13 is a cross-sectional view of the vent portion of Figure 4.

Claims

1. A protective film frame for mounting a protective film on a photomask by attaching the protective film to the photomask, the protective film including a film for transmitting exposure light and a support portion for supporting the outermost edge region of the film, the protective film frame comprising: a pair of frame members, each formed to match the shape of a support portion, coupled and overlapping each other by their plate surfaces to create a double-layer structure, and each of the frame members having a recessed portion in a corresponding area on a relatively inner surface, the recessed portion forming an exhaust hole laterally opening from the plate surfaces in the coupled state; and a filter disposed in the exhaust hole between the pair of frame members to block the exhaust hole; wherein when the filter is positioned between the frame members, the tubular cross-sectional structure of the filter forms a double-layer structure in the direction of air inflow / outflow through the exhaust hole to have a dual filtration effect.

2. The protective membrane frame of claim 1, wherein a plurality of the recesses are formed on each of the frame members to form a plurality of the vent holes.

3. The protective membrane frame of claim 1, wherein the height of the filter in cross-section is greater than the height of the vent hole.

4. The protective membrane frame of claim 1, wherein a receiving groove is formed on the bottom surface of one of the recesses to accommodate the filter in contact with a portion of the bottom surface.

5. The protective film frame of claim 4, wherein the receiving groove is formed along one of the longitudinal directions of the bottom surface.

6. The protective membrane frame of claim 5, wherein one cross-section of the receiving groove has a partially arcuate shape, and the filter is formed to have a cross-section with a circular shape.

7. The protective membrane frame of claim 5, wherein one cross-section of the receiving groove has a partial polygonal shape, and the filter is formed having one cross-section with a polygonal shape.

8. The protective membrane frame as claimed in claim 5, wherein the filter has a tubular shape.

9. The protective membrane frame as claimed in claim 8, wherein the filter has a plurality of pores.

10. The protective film frame of claim 5, wherein the length of the receiving groove along one of the longitudinal directions is greater than the length of one of the recessed portions.

11. The protective film frame of claim 10, wherein the sections extending beyond the recess at both ends of the receiving groove are formed with a cross-section having a semi-circular shape or a polygonal shape.

12. The protective membrane frame of claim 4, wherein an adhesive is applied to at least a portion of the receiving recess to provide adhesion to the filter.

13. A protective membrane frame as claimed in any of claims 1 to 12, wherein at least one of the pair of frame members has a pinhole on one side, the pinhole being formed to provide for securing one area of ​​the protective membrane frame from an external pin.

14. The protective membrane frame of any one of claims 1 to 12, wherein the frame members have a joint portion formed to be assembled with each other by mutual engagement.

15. The protective membrane frame of claim 14, wherein the joining portion includes a pair of protrusions formed on one inner surface of one of the frame members and a recess formed on one inner surface of the other of the frame members, the recess having a shape corresponding to the protrusions.

16. The protective membrane frame of claim 14, wherein the joint portion is formed between the plurality of such vent holes.

17. A protective membrane assembly comprising: a protective membrane frame as described in claim 1; and a protective membrane attached to the protective membrane frame.

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