An assembly consisting of a pellicle and its dedicated pellicle case

Abstract

To provide an assembly of a pellicle and a dedicated pellicle case thereof with reduced tendency to cause a deterioration in the flatness of the frame of a pellicle for lithography and, in turn, provide a method that prevents strain transfer to an exposure original plate.SOLUTION: A pellicle frame 2 and a tray part 9 of a dedicated pellicle case are each provided with structure means 4 for holding an adhesive layer 5 of a pellicle in a state of floating from the tray part of the dedicated pellicle case.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lithography pellicle used to protect against dust from lithography masks when manufacturing semiconductor devices such as LSIs and VLSIs, or liquid crystal display panels, and an assembly comprising the pellicle case for use therewith. [Background technology]

[0002] In the manufacture of semiconductors such as LSIs and VLSIs, or liquid crystal display panels, patterns are created by irradiating light onto semiconductor wafers or liquid crystal masters, but if dust adheres to the exposure master used in this case, the dust absorbs or bends the light, causing problems such as deformation of the transferred pattern, rough edges, and black staining of the underlying surface, resulting in impairment of dimensions, quality, appearance, etc. In this invention, "exposure master" is a general term for lithography masks and reticles (hereinafter also abbreviated as "masks").

[0003] These operations are usually carried out in a clean room, but since it is difficult to keep the mask clean even in this clean room, a method is used in which a pellicle that allows exposure light to pass through easily is attached to the surface of the mask to keep out dust. In this case, dust does not adhere directly to the surface of the mask, but to the pellicle film, so if the focus is aligned on the mask pattern during lithography, the dust on the pellicle film will not affect the transfer.

[0004] The basic structure of such a pellicle consists of a pellicle frame and a pellicle film stretched over it. The pellicle film is made of nitrocellulose, cellulose acetate, fluorine-based polymer, or the like, which allows good transmission of light used for exposure (g-line, i-line, 248 nm, 193 nm, etc.), and the pellicle frame is made of aluminum alloys such as A7075, A6061, A5052, stainless steel, polyethylene, or the like, which have been subjected to black anodizing treatment.

[0005] A good solvent for the pellicle film is applied to the upper surface (upper end surface) of the pellicle frame, and the pellicle film is attached to it and air-dried to adhere, or it is adhered using an adhesive such as acrylic resin, epoxy resin, fluororesin, etc. Furthermore, a protective sheet (hereinafter also referred to as a "separator") is provided on the lower surface (lower end surface) of the pellicle frame to attach a mask, which is made of a mask adhesive layer made of polybutene resin, polyvinyl acetate resin, acrylic resin, silicone resin, etc., and a release liner for protecting this adhesive layer.

[0006] The pellicle configured in this manner is installed to surround the pattern area formed on the surface of the mask and is provided to prevent dust from adhering to the mask, so that this pattern area and the outside of the pellicle are isolated from each other so that dust outside the pellicle does not adhere to the pattern surface.

[0007] In recent years, LSI design rules have been miniaturized to the sub-quarter micron level, and as a result, the wavelength of exposure light sources has been shortened. In other words, there is a shift from the previously mainstream KrF excimer laser (248 nm) to ArF excimer laser (193 nm) and ArF excimer laser (193 nm) immersion exposure.

[0008] As the wavelength of exposure light becomes shorter and the exposure resolution increases, there is concern that even pattern deformation and distortion, which were not a problem until now, will affect yield. This pattern deformation and distortion is largely due to deformation and distortion of the mask itself, and the main cause of these defects is said to be deformation and distortion that occurs when the pellicle is attached to the mask, and it is known that deformation and distortion of the pellicle itself is transmitted to the mask and has an adverse effect.

[0009] Therefore, attempts have been made to reduce the impact on the mask, and Patent Documents 1 and 2 describe lithography pellicles in which the surface flatness of the mask adhesive layer of the pellicle is 15 μm or less. However, even pellicles made with such a flatness of the adhesive layer of the pellicle have the problem that the completed shape of the pellicle may not be stably maintained when the pellicle is stored in a container after completion. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 5411200 [Patent Document 2] Patent No. 5999843 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in consideration of the above circumstances, and its object is to provide an assembly consisting of a highly flat lithography pellicle and a dedicated pellicle case that can stably reduce deformation and distortion of an exposure master.

[0012] Conventionally, highly flat lithography pellicles (hereinafter simply referred to as "highly flat pellicles") have been manufactured by controlling the flatness of rectangular pellicle frames (hereinafter simply referred to as "frames"). However, the inventors conducted repeated experiments in which, after the pellicle was completed, it was stored in a dedicated pellicle case (comprising a lid and a tray), and then the pellicle was removed and attached to a mask. As a result, they found that the effect of distortion on the mask differs even when pellicles manufactured under the same conditions are attached.

[0013] The inventors further investigated the cause and found that storing a pellicle in a dedicated pellicle case causes the mask adhesive layer (hereinafter simply referred to as "adhesive layer") with a protective sheet (separator) attached thereto to come into contact with the tray portion of the dedicated pellicle case, resulting in a deterioration in the flatness of the adhesive layer compared to the flatness immediately after manufacture. The inventors also confirmed that the degree of deterioration in the flatness of the adhesive layer varies from one pellicle to another, and that a smaller deterioration in flatness results in less distortion of the mask when the pellicle is attached. These findings were first discovered by the inventors, and the inventors are the first to focus on and clarify the causal relationship that storing a pellicle in a conventional, general pellicle case deteriorates the flatness of the adhesive layer, which in turn leads to deformation and distortion of the mask when the pellicle is attached, and ultimately to deformation and distortion of the pattern.

[0014] Furthermore, the inventors have verified that a pellicle in which the adhesive layer is held in a non-contact state with the tray portion of a dedicated pellicle case, without being stored in a dedicated pellicle case after completion, results in less distortion of the mask, leading to the present invention. [Means for solving the problem]

[0015] In other words, the assembly of the lithography pellicle and its dedicated pellicle case of the present invention is characterized in that the adhesive surface of the adhesive layer is held in a floating state above the tray portion of the dedicated pellicle case so as not to come into contact with the tray portion, and is stored in the dedicated pellicle case.As a structural means for holding the adhesive layer in a floating state above the tray portion of the dedicated pellicle case, for example, a cutout portion (step) or protrusion is provided on the outer periphery of the pellicle frame, and a structure is installed in the tray portion of the dedicated pellicle case to receive the cutout portion or protrusion on the outer periphery of the pellicle frame. Taking into consideration the practical aspects of the pellicle, and in order to make it compatible with current pellicle removal devices (pellicle auto-mounters), it is desirable to provide a structure that does not interfere with the existing jig holes provided in two places on each long side and that does not create resistance when pulling the pellicle upward, so that there is no need to change the settings on the pellicle auto-mounter and it can be used as is, and the pellicle can be moved and removed smoothly using the conventional operation without any additional operations, and the adhesive layer of the pellicle can be stored in a floating state without contacting the tray portion. [Effects of the Invention]

[0016] According to the present invention, when the completed pellicle is stored in a dedicated pellicle case, the surface to which the protective sheet (separator) of the adhesive layer is attached is stored in a floating state so that it does not come into contact with the dedicated pellicle case. This allows the flatness of the sheet-attached surface of the adhesive layer to be maintained at the same level as before it was stored in the case, and a highly flat lithography pellicle can be provided that can minimize the impact on mask distortion when the pellicle is attached to a mask. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view of one embodiment of an assembly of a pellicle and its dedicated pellicle case according to the present invention. [Figure 2]1 is a schematic cross-sectional view of one embodiment of an assembly of a pellicle and its dedicated pellicle case according to the present invention. [Figure 3] FIG. 1 is a schematic cross-sectional view of one embodiment of an assembly of a pellicle according to the present invention and its dedicated pellicle case, in which a protective sheet (separator) for the adhesive layer is not used. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these embodiments. A lithography pellicle stored according to the present invention is characterized in that the flatness of the mask-attaching adhesive layer does not deteriorate even when the pellicle is stored in a dedicated pellicle case after completion. FIG. 1 is a schematic cross-sectional view of an assembly 10 of a pellicle and its dedicated pellicle case according to the present invention, showing an embodiment in which a separator 3 is provided. FIG. 2 is a schematic cross-sectional view of an assembly 10 of a pellicle and its dedicated pellicle case according to the present invention, showing an embodiment in which a notched step 6 is provided as a structural means for preventing the pellicle from protruding outside the pellicle frame 2. FIG. 3 is a schematic cross-sectional view of an assembly 10 of a pellicle and its dedicated pellicle case according to the present invention, showing an embodiment in which a separator is not provided.

[0019] To achieve the above features, the outer surface of the pellicle frame 2 and the tray portion 9 of the dedicated pellicle case must each have a distinctive shape. As a specific example, the pellicle frame can be provided with an optional protrusion or notch (step) on the outer surface of the frame so that the adhesive surface (lower end surface) of the adhesive layer 5 on the lower end surface of the frame can be stabilized in a floating state when stored in the dedicated pellicle case. In this case, the dedicated pellicle case needs a structure (structural means) shaped to receive the protrusion or step on the frame as the structural means 4 for supporting the pellicle. As shown in Figures 1 to 3, the dedicated pellicle case includes a lid portion 8 and a tray portion 9. In Figures 1 to 3, reference numeral 1 denotes a pellicle membrane.

[0020] As a method for placing the adhesive layer in a floating state within a dedicated pellicle case, a plurality of holes can be formed on the outer surface of the pellicle frame, and a structural means consisting of the same number of protrusions as the holes and a supporting structure for the protrusions can be provided on the tray portion of the dedicated pellicle case, such as a structural means having pin-shaped protrusions, which can be inserted into the holes to hold the pellicle. However, in this case, the operation of removing the pins must be added to the operation of removing the pellicle from the dedicated pellicle case. Currently, a dedicated device called a pellicle automounter is used to remove a pellicle from a dedicated pellicle case, so a pellicle frame and dedicated pellicle case structure that allows pellicle removal using conventional operations is required. Considering this reality, this embodiment will take time to implement and cannot be considered the best mode.

[0021] In the present invention, by combining a pellicle frame having the above-described structure with its dedicated pellicle case, i.e., by assembling it, the adhesive surface of the mask-attaching adhesive layer can be kept floating and out of contact with the tray portion until the pellicle is stored in the dedicated pellicle case after completion and attached to the mask.This allows the flatness of the pellicle immediately after completion to be completely maintained, and significantly reduces pellicle-induced distortion to the flat surface of the mask that occurs when the pellicle is attached.

[0022] In the present invention, it is preferable that the structure of the outer surface of the pellicle frame for lithography has as little protrusion as possible toward the outer periphery. Therefore, it is a meaningful option to reduce the coating end surface of the mask-attaching adhesive layer and provide a step on the outside of the pellicle frame.

[0023] The shape and number of structural means (protrusions, cutouts, etc.) provided on the pellicle frame and the tray portion of the dedicated pellicle case for storing the mask-attaching adhesive layer in a floating state within the dedicated pellicle case must be such that the pellicle can be held securely and stably inside the case.

[0024] Furthermore, when the pellicle made by the present invention is stored in a dedicated pellicle case, the adhesive layer for attaching the mask can be kept floating in the air, making it possible to eliminate the need for the commonly used protective sheet (separator) for the adhesive layer for attaching the mask.

[0025] If the separator is eliminated, not only will the materials and manufacturing steps be reduced, but there will also be no need to remove and attach the separator. Also, since the end surface of the adhesive layer for attaching the mask will not be subjected to any force immediately after the pellicle is completed, it is expected that the distortion of the flat surface of the mask that occurs when the pellicle is attached to the mask will be further reduced and stabilized. [Example]

[0026] Next, examples of the present invention will be specifically described. The examples and comparative examples are examples of masks, but it goes without saying that the results can be similarly applied to reticles.

[0027] The effects of the present invention were evaluated as follows: First, the flatness of the mask substrate used for attachment was measured using Tropel's FlatMaster, then the highly flat pellicle to be evaluated was attached to this mask substrate, the flatness of the mask substrate was measured in the same way, and the difference in mask distortion before and after attachment (difference in flatness) was measured, and this difference (the amount of increase in mask distortion due to attachment) was taken as the performance of each pellicle.

[0028] [Example of standards] In addition, as a comparison to confirm the effect of the present invention, the mask attachment behavior of a pellicle not housed in a case was also confirmed (reference example).

[0029] Specifically, a reference pellicle frame was prepared with outer dimensions of 149 mm x 115 mm x 3.15 mm (height), a frame width of 2 mm, four corners curved with an outer radius of 5 mm and an inner radius of 3 mm, a black anodized aluminum surface, and a frame flatness of 9 μm. A pellicle was fabricated using this frame. A separator to protect the adhesive layer was not provided.

[0030] Next, the flatness of the prepared mask was measured using Tropel's FlatMaster and found to be 305 nm. The standard pellicle was then attached to the mask substrate under conditions of a 5 kg weight for 30 seconds, and the mask flatness was measured again and found to be 340 nm. In other words, the difference in distortion of the mask substrate before and after attachment was 35 nm.

[0031] [Example 1] A frame 2 was prepared as a pellicle frame. The frame dimensions were 149 mm × 115 mm × 3.15 mm, the frame width was 2 mm, and the four corners had an outer radius of 5 mm and an inner radius of 3 mm. The surface was black anodized. A cutout step (cutout portion) 6 with a thickness of 1 mm and radius of 1 mm was provided on each of the outer surfaces of the four corners of the frame, 1 mm from the bottom end (see Figure 2). The frame flatness was 8 μm. A pellicle was fabricated using this frame 2. No separator was provided to protect the adhesive layer (see Figure 3). The completed pellicle was stored in a dedicated pellicle case. The tray portion 9 of the dedicated pellicle case had a structure (structural means for supporting the pellicle) 4 shaped to support the pellicle, receiving the cutout steps 6 provided on the outer surfaces of the four corners and allowing the adhesive layer to be stored floating.

[0032] Next, the flatness of a prepared mask (not shown) similar to that used in the reference example above was measured using Tropel's FlatMaster, and the mask flatness was found to be 301 nm. The pellicle was removed from the dedicated pellicle case, and the pellicle was attached to the mask substrate under a 5 kg weight for 30 seconds. The mask flatness was then measured again, and found to be 337 nm. In other words, the difference in distortion of the mask substrate before and after attachment was 36 nm.

[0033] [Example 2] A frame 2 having the same shape as in Example 1 was prepared, and the flatness of this frame was measured and found to be 7 μm. A pellicle was produced in the same manner as in Example 1, and finally, a separator 3 was attached to the adhesive surface of the pressure-sensitive adhesive layer, and then the pellicle was stored in a dedicated pellicle case having the same shape as in Example 1. Next, the flatness of a prepared mask similar to that used in the reference example was measured using Tropel's FlatMaster, and the mask flatness was found to be 297 nm. The pellicle was removed from the dedicated pellicle case, the separator 3 was peeled off, and the pellicle was attached to the mask substrate under a 5 kg weight for 30 seconds. The mask flatness was then measured again, and found to be 336 nm. In other words, the difference in distortion of the mask substrate before and after attachment was 39 nm.

[0034] [Example 3] A pellicle frame 2 was prepared, with outer dimensions of 149 mm x 115 mm x 3.15 mm and a frame width of 2 mm. Four notch steps 6, as shown in Figure 2, were provided at four locations approximately 60 mm from the center of the long sides of the frame. The four corners were black anodized with an outer radius of 5 and an inner radius of 3. The flatness of the frame was measured and found to be 8 μm. A pellicle was fabricated using this frame 2. A separator 3 to protect the adhesive layer 5 was not provided. The completed pellicle was stored in a dedicated pellicle case. The tray portion 9 of the dedicated pellicle case had a structural means 4 that could receive the four notch steps 6 provided on the long sides of the frame and store the adhesive layer in a floating position. Next, the flatness of a prepared mask similar to that used in the reference example was measured using Tropel's FlatMaster, and the mask flatness was found to be 303 nm. The pellicle was removed from the dedicated pellicle case, and the pellicle was attached to the mask substrate under a 5 kg weight for 30 seconds. The mask flatness was then measured again, and found to be 339 nm. In other words, the difference in distortion of the mask substrate before and after attachment was 36 nm.

[0035] [Example 4] A frame 2 having the same shape as in Example 3 was prepared, and the flatness of this frame was measured and found to be 8 μm. A pellicle was produced in the same manner as in Example 3, and finally, a separator 3 was attached to the attachment surface of the pressure-sensitive adhesive layer, and then the pellicle was stored in a dedicated pellicle case having the same shape as in Example 3. Next, the flatness of a prepared mask similar to that used in the reference example was measured using Tropel's FlatMaster, and the mask flatness was found to be 299 nm. The pellicle was removed from the dedicated pellicle case, the separator was peeled off, and the pellicle was attached to the mask substrate under a 5 kg weight for 30 seconds. The mask flatness was then measured again, and found to be 337 nm. In other words, the difference in distortion of the mask substrate before and after attachment was 38 nm.

[0036] [Comparative Example 1] A frame of the same shape as in Example 1 was prepared, and the flatness of this frame was measured, finding it to be 7 μm. A pellicle was produced in the same manner as in Example 1, and finally, a separator was attached to the adhesive surface of the adhesive layer, and the pellicle was then stored in a general pellicle case. Unlike the dedicated pellicle cases used in Examples 1 to 4, the pellicle was stored in a state where the adhesive layer protected by the separator was placed on the mounting base of the pellicle tray. Next, the flatness of a prepared mask similar to that used in the reference example was measured using Tropel's FlatMaster, and the mask flatness was found to be 305 nm. The pellicle was removed from the pellicle case, the separator was peeled off, and the pellicle was attached to the mask substrate under a 5 kg weight for 30 seconds. The mask flatness was then measured again, and found to be 367 nm. In other words, the difference in distortion of the mask substrate before and after attachment was 62 nm.

[0037] Table 1 summarizes the above results.

[0038] First, the significant improvement brought about by the present invention was demonstrated by the fact that the Examples, in which the "mask adhesive is floating above the tray," significantly reduced the amount of strain transferred to the flat surface of the mask during pellicle attachment compared to Comparative Example 1, in which the "mask adhesive layer is placed on the tray." This proves that the mask adhesive layer's contact with the tray causes deterioration in the flatness of the adhesive, and provides an effective solution to this problem.

[0039] Next, the fact that Examples 1 and 3 had almost the same results as the reference example in which case storage was skipped means that the combination (assembly) of the dedicated pellicle case and pellicle of the present invention has successfully designed a highly reliable case that enables storage of separator-free pellicles.

[0040] On the other hand, Examples 2 and 4 prove that even if a separator is attached, i.e., even if the pressure applied during attachment causes some deterioration in the flatness of the adhesive layer, if the mask is stored in a special pellicle case that keeps the "mask adhesive layer floating above the tray portion," there will be almost no further deterioration.

[0041] Furthermore, by attaching a separator, Examples 2 and 4 can enjoy the effect of preserving adhesive strength by preventing evaporation and avoiding dust capture by the separator, and since the adhesive layer is not in contact with the tray part, direct vibration from the tray part can be avoided, thereby making them excellent embodiments that can promote the maintenance of high flatness.

[0042] [Table 1]

[0043] As described above, from the results of Examples 1 to 4, when storing the pellicle in a dedicated pellicle case, by storing the pellicle without contacting the attachment end surface of the mask adhesive layer with the tray portion of the case, the attachment end surface of the adhesive layer can be attached to the mask while maintaining the excellent flatness it had immediately after completion. As a result, distortion of the mask when the pellicle is attached to the mask can be reduced.

[0044] Furthermore, by not using a separator, which is used to protect the adhesive layer, it was confirmed that the force acting on the adhesive layer's attachment end surface can be eliminated, the flatness of the adhesive layer's attachment end surface can be maintained at the same flatness as the frame immediately after the pellicle is completed, and the transfer of distortion during mask attachment can be further reduced.

[0045] In the examples of the present invention, an embodiment in which a protrusion such as a pin is inserted into the pellicle frame as a structural means for storing the pellicle in a dedicated pellicle case in a floating state was not implemented. The reason for this is that it was considered possible to directly accommodate the removal operation of a currently used pellicle automounter. However, the scope of the present invention also includes an embodiment in which the pellicle is fixed to the pellicle frame 2 using a structure such as a pin 7 attached to the outer surface of the frame, as shown in Figures 1 and 3.

[0046] In order to achieve the effects of the present invention, the essential elements of the pellicle and the essential elements of the dedicated pellicle case must coexist and cooperate, and therefore the subject of the invention is the assembly of the pellicle and its dedicated pellicle case. [Explanation of symbols]

[0047] 1. Pellicle membrane 2 Pellicle Frame 3 Separator 4. Structural means for supporting the pellicle 5. Adhesive layer 6 Cutout step (cutout part) 7 Pins as part of the structural means supporting the pellicle 8 Lid of dedicated pellicle case 9 Tray part of dedicated pellicle case 10 Assembly of pellicle and its dedicated pellicle case

Claims

1. An assembly consisting of a pellicle and a dedicated pellicle case, wherein the pellicle includes a rectangular pellicle frame and an adhesive layer for attaching the pellicle to an exposure master plate and a separator for protecting the adhesive layer, the adhesive layer being provided on the lower end surface of the pellicle frame, and the dedicated pellicle case includes a lid portion and a tray portion; the pellicle frame and the tray portion are each provided with a structural means for holding the separator in a floating state above the tray portion of the dedicated pellicle case, the pellicle is a pellicle for semiconductor manufacturing and is used for exposure with an exposure light source having a wavelength of 193 nm or less; the structural means provided on the pellicle frame are provided at four corners of the pellicle frame, An assembly consisting of a pellicle and its dedicated pellicle case, characterized in that the structural means provided on the pellicle frame and the tray portion allow the pellicle to move smoothly without any other movement when lifted upward.

2. An assembly consisting of a pellicle and a dedicated pellicle case, wherein the pellicle includes a rectangular pellicle frame and an adhesive layer provided on the lower end surface thereof for attaching to an exposure master, and the dedicated pellicle case includes a lid portion and a tray portion; the pellicle frame and the tray portion are each provided with structural means for holding the pressure-sensitive adhesive layer in a floating state above the tray portion of the dedicated pellicle case, The pellicle is housed in the dedicated pellicle case without a separator for protecting the adhesive layer being provided on the lower end surface of the pellicle frame, the pellicle is a pellicle for semiconductor manufacturing and is used for exposure with an exposure light source having a wavelength of 193 nm or less; the structural means provided on the pellicle frame are provided at four corners of the pellicle frame, An assembly consisting of a pellicle and its dedicated pellicle case, characterized in that the structural means provided on the pellicle frame and the tray portion allow the pellicle to move smoothly without any other movement when lifted upward.

3. An assembly comprising a pellicle described in any one of claims 1 to 2 and its dedicated pellicle case, wherein the structural means provided on the pellicle frame are provided at a total of four locations at positions at least 60 mm away from the center portion of each long side of the pellicle frame.

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