Structure and Method of a Reticle Cassette with a Inspection Window

Abstract

Embodiments of the present invention relate to a structure and method of a reticle box having an inspection window. Some embodiments of the present invention provide a structure and method of a reticle box. The reticle box includes a base configured to support a reticle and a cover detachably coupled to the base. The cover includes a window that allows radiation having a wavelength between about 400 nm and about 700 nm to pass through with a transmittance greater than 70%.

Description

Technical Field

[0001] Embodiments of the present invention relate to a structure and method of a photomask cassette having an inspection window. Background Art

[0002] A photomask is fabricated to form a circuit pattern thereon and is used in a semiconductor manufacturing process to transfer the circuit pattern onto a wafer. The fidelity and integrity of the photomask pattern are crucial for the success of mass production of wafers and thus many techniques have been proposed to fabricate the photomask and protect the photomask pattern from damage or contamination. In modern semiconductor manufacturing processes, a photomask cassette is typically used to accommodate, protect, and transport the photomask. Summary of the Invention

[0003] According to an embodiment of the present invention, a photomask cassette includes: a base configured to support a photomask; and a cover configured to form a sealed space with the base, the cover including a window having: a window body; and transparent films on both sides of the window body, wherein the window is configured to allow radiation of a predetermined wavelength to pass through with a transmittance greater than 70%.

[0004] According to another embodiment of the present invention, a photomask cassette includes: a base configured to support a photomask; and a cover detachably coupled to the base, wherein the cover includes a window that allows radiation having a wavelength between about 400 nm and about 700 nm to pass through with a transmittance greater than 70%.

[0005] According to yet another embodiment of the present invention, a method of manufacturing a photomask includes: performing a first operation to form a pattern on the photomask; placing the photomask in a photomask cassette including a base and a cover configured to form a sealed space with the base, and the cover including a window configured to allow radiation of a predetermined wavelength to pass through; and performing an inspection operation on the photomask through the window. Brief Description of the Drawings

[0006] Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying Figure 1 It should be noted that, in accordance with standard practice in the industry, various components are not drawn to scale. In fact, for clarity of discussion, the dimensions of various components may be arbitrarily increased or decreased.

[0007] Figure 1 is a schematic cross-sectional view of a photomask cassette according to some embodiments.

[0008] Figure 2A and 2B is a schematic plan view of the photomask cassette in Figure 1 according to some embodiments.

[0009] Figures 3A to 3LIs a schematic cross-sectional view of an intermediate stage of a method for manufacturing a photomask according to some embodiments.

[0010] Figures 4A to 4E Is a schematic cross-sectional view of an intermediate stage of a method for repairing a photomask according to some embodiments.

[0011] Figures 5A to 5E Is a schematic cross-sectional view of an intermediate stage of a method for repairing a photomask according to some embodiments.

[0012] Figures 6A to 6E Is a schematic cross-sectional view of an intermediate stage of a method for repairing a photomask according to some embodiments.

[0013] Figure 7 Is a flowchart of a method for manufacturing a photomask according to some embodiments.

[0014] Figure 8 Is a flowchart of a method for manufacturing a semiconductor device according to some embodiments. Detailed Description

[0015] The following disclosure provides many different embodiments or examples for implementing different components of the provided subject matter. Specific examples of components and arrangements are described below to simplify the disclosure. Of course, these are only examples and are not intended to be limiting. For example, in the description, the formation of a first component above or on a second component may include embodiments in which the first component and the second component are formed in direct contact and may also include embodiments in which additional components may be formed between the first component and the second component such that the first component and the second component may not be in direct contact. Additionally, the disclosure may repeat reference numerals and / or letters in various examples. This repetition is for simplicity and clarity purposes and does not inherently indicate a relationship between the various embodiments and / or configurations discussed.

[0016] Furthermore, spatial relative terms (such as "below", "beneath", "lower", "above", "upper", etc.) may be used herein for ease of description to describe the relationship of one component or element to another component or element, as illustrated in the various figures. The spatial 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 oriented in other ways (rotated 70 degrees or in other orientations) and the spatial relative descriptive terms used herein may thus be understood accordingly.

[0017] While the numerical ranges and parameters set forth in this disclosure are approximations of the broad scope thereof, the numerical values set forth in specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in the corresponding testing measurements. Also, as used herein, the terms "about," "substantially," and "essentially" generally mean within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, when considered by those of ordinary skill in the art, the terms "about," "substantially," and "essentially" mean within an acceptable standard. Except for operating / working examples, or unless otherwise expressly specified, all numerical ranges, amounts, values, and percentages (e.g., those of numerical ranges, amounts, values, and percentages of quantities such as materials, durations, temperatures, operating conditions, quantity ratios, and the like disclosed herein) are to be understood as being modified in all instances by the term "about," "substantially," or "essentially." Accordingly, unless indicated to the contrary, the numerical parameters set forth in this disclosure and the appended claims are approximations that may vary as desired. At the very least, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Ranges may be expressed herein as from one endpoint to another endpoint or between two endpoints. Unless otherwise specified, all ranges disclosed herein include the endpoints.

[0018] Embodiments of the present disclosure discuss the structure and method of operation of a photomask cassette. Embodiments of the present disclosure also discuss methods of manufacturing and repairing a photomask. Generally, a photomask cassette includes a base and a cover that form a sealed space for accommodating a photomask. The proposed photomask cassette is characterized by a window in the cover, wherein the window allows for early detection of pattern defects during the manufacturing process of the photomask. An inspection operation can be performed immediately after a specific manufacturing step to check whether a defect has occurred due to this manufacturing step. Thus, defect detection can be performed in a timely and more accurate manner, and early repair can be achieved accordingly.

[0019] Throughout this disclosure, the terms "photomask," "photolithography mask," and "mask" are used interchangeably to refer to a device used in an optical lithography operation, in which an opaque image of a circuit pattern is formed on a substrate. The substrate may be transparent. An image of the circuit pattern on the photomask is transferred to the substrate or wafer by a radiation source of the optical lithography operation. Radiation from the radiation source irradiates the substrate through or reflected by the photomask.

[0020] Figure 1FIG. 1 is a schematic cross-sectional view of a reticle pod 10 according to some embodiments. The reticle pod 10 is for accommodating a reticle 108. In some embodiments, the reticle 108 is a transmissive type reticle, a reflective type reticle, or another suitable type of reticle. The reticle pod 10 includes a base 110 and a cover 120 located above the base 110. The cover 120 is removably coupled to the base 110 to form an enclosed space therein for fixing the reticle 108.

[0021] Figure 2A and 2B are respectively schematic plan views of the base 110 and the cover 120 of the reticle pod 10 according to some embodiments Figure 1 in FIG. 2. Figure 1 The cross-sectional view of FIG. 1 is taken along Figure 2A and 2B section line AA in FIG. 2. Referring to Figure 1 and 2A , the base 110 includes a platform 102, a reticle holder 104, and a latch 106. In some embodiments, the platform 102 is for supporting the reticle 108 via the reticle holder 104. The platform 102 can be formed of PEEK (polyetheretherketone), PMMA (polymethyl methacrylate), or other suitable materials. The platform 102 can have a circular or quadrilateral shape, such as a rectangular or square shape. In some embodiments, the reticle 108 has a diameter or width W1 between about 14 cm and about 16 cm (e.g., 15 cm). In some embodiments, the platform 102 has a width W2 between about 22 cm and about 30 cm. In some embodiments, the width W2 of the platform 102 is between about 150% and about 200% of the width W1 of the reticle 108.

[0022] In some embodiments, the reticle holder 104 is for supporting the reticle 108 such that the reticle is suspended above the platform 102 by a distance. In some embodiments, the reticle holder 104 is formed of PEEK, PMMA, or other suitable materials. Referring to Figure 2A , in a top-down perspective view, the reticle holders 104 can be placed around the corners of the reticle 108. For example, two reticle holders 104 are placed closely adjacent to the corners of the reticle 108. Referring to Figure 1 , each of the reticle holders 104 can include a groove 104R which, in a cross-sectional view, is adjacent to the upper surface and can be configured to receive the reticle 108. In some other embodiments, the groove 104R of the reticle holder 104 is replaced by a chamfer which faces the reticle 108 and is configured to receive the reticle 108.

[0023] Latch 106 is used to couple the base 110 to the cover 120. In some embodiments, the cover 120 includes a slot (not shown) corresponding to the latch 106 for coupling to the base 110. The latch 106 can be implemented by mechanical or electronic latching components known in the art. Through the latch 106, a closed space is formed by the base 110 and the cover 120 to hold and fix the photomask 108.

[0024] Reference Figure 1 and 2B , the cover 120 removably houses the base 110 and is configured to cover the photomask 108 from above. The cover 120 includes a frame 112 and a window 114. The frame 112 constitutes the main body of the cover 120 and provides physical support and mechanical strength to the cover 120.

[0025] Depending on requirements, the frame 112 can have various configurations. For example, in a cross-sectional view, the frame 112 has a stepped shape, where a central portion 112C is higher than a peripheral portion 112P surrounding the central portion. In some embodiments, the cover 120 or the frame 112 has a height between about 5 cm and about 8 cm. The frame 112 can be formed of an electrically insulating material (e.g., a plastic or polymeric material). In some embodiments, the frame 112 includes PEEK or PMMA. In some embodiments, the frame 112 is formed of an opaque material.

[0026] The window 114 is disposed in a central portion 120C of the cover 120, which is higher than a peripheral portion 120P of the cover 120. The frame 112 can include an opening in the central portion 120C for receiving the window 114 therein. The window 114 can be laterally surrounded by the frame 112. In some embodiments, the frame 112 includes support beams 117 around the corners of the window 114. The support beams 117 can form a right triangle with the side of the window 114 (to which the support beams 117 are connected), where the support beams 117 serve as the hypotenuse of the triangle and support the window 114 from the bottom of the window 114.

[0027] The reticle 108 includes a circuit pattern on an upper side facing the window 114. The base 110 and the frame 112 are generally formed of an opaque material. Thus, when the reticle cassette 10 is in a closed state, the window 114 allows for manual or machine inspection of the reticle 108. The window 114 may be formed by a window body 116 and a film 118 coated on the window body 116. In some embodiments, the window 114 includes a transparent material. During an inspection operation, radiation (e.g., a laser beam) from a radiation source RS may be emitted to irradiate the reticle 108. The patterned radiation reflected from the reticle 108 carries the geometry of the circuit pattern on the reticle 108. Comparison of the reflected laser beam pattern with the original pattern can help detect defects in the circuit pattern, such as foreign contaminants, particles, protrusions, material loss (intrusion), excess material (extension or bridging), necking, and pinholes. In some embodiments, the window 114 allows radiation from the radiation source RS to pass through such that the radiation does not react with the photoresist material of the reticle 108. In some embodiments, the window 114 allows radiation having a wavelength in the green light range to pass through, where the wavelength of the radiation is between about 400 nanometers (nm) and about 700 nm. In some embodiments, the radiation has a wavelength between about 500 nm and about 560 nm. If radiation having a wavelength greater than about 700 nm is used as inspection radiation, the energy of the reflected light beam may not be sufficient to accurately transmit the circuit pattern of the reticle 108. If radiation having a wavelength less than about 400 nm is used as inspection radiation, the energy of the inspection radiation may cause damage or an undesired reaction of the material in the reticle 108. For example, the photoresist material in the reticle 108 may react with the radiation in a manner that causes a change in properties.

[0028] In some embodiments, the window 114 has a quadrilateral shape, such as a rectangular or square shape. When the reticle 108 is placed in the reticle cassette 10, the window 114 is aligned with the reticle 108. In some embodiments, when the reticle 108 is placed in the reticle cassette 10, the window 114 covers the entire reticle 108 such that radiation can be projected through the window 114 onto the entire upper surface of the reticle 108 and reflected back to the detection circuit. In some embodiments, the window 114 covers the entirety of the pattern area within which the circuit pattern of the reticle 108 is formed. The window 114 may have a width W3 that is greater than or substantially equal to the width W1 of the reticle 108. In some embodiments, the width W3 is between about 15 cm and about 30 cm or between about 18.75 cm and about 26.25 cm. In some embodiments, the width W3 is between about 125% and about 175% of the width W1 of the reticle 108. In some embodiments, the window 114 has an area between about 120% and about 250% of the area of the reticle 108.

[0029] In some embodiments, the window 116 has a thickness between about 0.05 cm and about 1 cm. In some embodiments, the window 116 can be formed of a transparent material such as glass. The window 116 can include fused silica (SiO 2 ), fused quartz, calcium fluoride (CaF 2 ), silica-titania alloy, sapphire, or other suitable materials without defects. In some embodiments, the window 116 has a transmittance greater than about 70%, greater than about 80%, or greater than about 90% with respect to inspection radiation.

[0030] In some embodiments, the film 118 is coated on both the outer surface (film 118A) and the inner surface (film 118B) of the window 116, where the film 118A faces upward and the film 118B faces downward (i.e., faces the base 110). The film 118 can be coated on the window 116 using physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), or another suitable deposition process. The film 118 can improve the inspection efficiency and protection of the photomask 108. In some embodiments, the film 118 has a transmittance greater than about 65%, greater than about 70%, or greater than about 80% with respect to inspection radiation. In addition, the film 118 can facilitate the removal of static charges generated during the transportation of the photomask cassette 10 or contact with the photomask cassette, and thus can reduce or eliminate damage caused by electrostatic discharge of the photomask 108 or the accumulation of contaminant particles generated by static charges. In some embodiments, the film 118 is a conductive film and includes a conductive material for conducting static charges, such as aluminum zinc oxide (AZO), indium tungsten oxide (ITO), fluorine-doped tin oxide (FTO), carbon nanotubes, or a combination thereof.

[0031] In some embodiments, the film 118A or 118B has a deposition thickness T measured across the side of the form 116, and the deposition thickness is between about 20 nm and about 200 nm. A film 118A or 118B having a thickness less than about 20 nm may not provide sufficient ability to conduct static charge. A film 118A or 118B having a thickness greater than about 200 nm may not provide sufficient transmittance for the inspection radiation of interest. In some embodiments, if the inspection radiation has a larger wavelength, the thickness of the film 118A or 118B is reduced. In some embodiments, for inspection radiation having a wavelength between 400 nm and about 700 nm, the film 118 formed of AZO has a thickness of about 20 nm. In some embodiments, for inspection radiation having a wavelength between about 400 nm and about 500 nm, the film 118 formed of ITO has a thickness between about 20 nm and about 100 nm. In some embodiments, for inspection radiation having a wavelength between about 500 nm and about 600 nm, the film 118 formed of ITO has a thickness between about 90 nm and about 110 nm (e.g., 100 nm). In some embodiments, for inspection radiation having a wavelength between about 600 nm and about 700 nm, the film 118 formed of ITO has a thickness between about 100 nm and about 200 nm.

[0032] In some embodiments, the inspection operation is performed at atmospheric pressure. Although the opportunity for contamination at atmospheric pressure may be higher than that in a vacuum environment, the reticle 108 can still be well protected by the reticle cassette 10 during the inspection operation because the reticle 108 is inspected within the sealed reticle cassette 10. The inspection radiation can be emitted through the window 114 onto the pattern of the reticle 108 without exposing the reticle 108 to the outside of the reticle cassette 10, and the possibility of contamination can be reduced.

[0033] Figures 3A to 3L is a schematic cross-sectional view of an intermediate stage of a method of manufacturing a reticle 108 according to some embodiments. The reticle 108 can be classified as a transmissive type, a reflective type, or another suitable type. In the depicted example, a transmissive type reticle 108 is illustrated. It should be understood that additional operations can be provided before, during, and after the process shown in Figures 3A to 3L and some of the operations described below can be replaced or eliminated for additional embodiments of the method. The order of the operations can be interchangeable. In addition, the same or similar configurations, structures, materials, operations, or processes of the foregoing embodiments can be used in this embodiment and detailed explanations can be omitted.

[0034] Refer to Figure 3A, receiving or providing a photomask 108, and the photomask includes a stack of a substrate 302, a phase shift layer 304, a shielding layer 306, a mask layer 308, and a photoresist layer 310 located above each other. It should be understood that other layers may be added to the stack of the photomask 108 as appropriate.

[0035] In some embodiments, the substrate 302 is configured to allow optical lithography radiation to pass through. The substrate 302 can be a low temperature expansion material (LTEM). In some embodiments, the substrate 302 is a transparent material and can be formed of fused silica, fused quartz, calcium fluoride (CaF 2 ), silicon carbide, silicon oxide - titanium oxide alloy, and / or other suitable LTEMs.

[0036] In some embodiments, the phase shift layer 304 is configured to change or shift the phase of the incident radiation passing through, so as to improve image sharpness. In some embodiments, the phase shift layer 304 includes molybdenum silicon nitride (MoSiN), molybdenum silicide (MoSi), molybdenum silicon oxynitride (MoSiON), titanium nitride, titanium silicon nitride, silicon nitride, or other suitable materials.

[0037] In some embodiments, the shielding layer 306 is configured to absorb an undesired portion of the incident optical lithography radiation for forming patterned lithography radiation on a workpiece. In some embodiments, the shielding layer 306 includes chromium or its compounds, such as CrN, CrON, and CrO. In some embodiments, the shielding layer 306 includes molybdenum or its compounds, such as MoSi, MoSiN, and MoSiON. In some embodiments, the shielding layer 306 includes tantalum or its compounds, such as TaN, TaON, TaB, TaBN, TaHfN, TaHf, TaSi, TaSiN, TaGe, TaGeN, TaZrN, and TaZr.

[0038] In some embodiments, the mask layer 308 includes silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or other masking materials. In some embodiments, the photoresist layer 310 includes a photosensitive material used as a positive tone photoresist or a negative tone photoresist.

[0039] Each of the phase shift layer 304, the shielding layer 306, the mask layer 308, and the photoresist layer 310 can be deposited above the substrate 302 by PVD, CVD, ALD, spin coating, or another suitable deposition technique.

[0040] Still referring to Figure 3A, an exposure operation is performed on the photoresist layer 310 to transfer a predetermined circuit pattern to the photoresist layer 310. Accordingly, a portion 312 of the photoresist layer 310 corresponding to the circuit pattern is exposed. An electron beam (e-beam) writer can be used to expose the portion 312. The electron beam writer generates a geometrically confined electron stream that irradiates a selected area of the photoresist layer 310. Those skilled in the art will recognize that any other suitable writer can be used to irradiate the selected area of the photoresist layer 310. In the case of a positive-tone photoresist layer 310, the irradiated area is made soluble in the developer and the unirradiated area remains insoluble in the developer.

[0041] In some embodiments, a post-exposure bake operation is performed to enhance the exposure performance and cause the exposed portion 312 to extend through the thickness of the photoresist layer 310.

[0042] Reference Figure 3B , a developer is used to perform a development operation to remove the exposed portion 312. A trench 314 is formed in the photoresist layer 310 and the upper surface of the exposure mask layer 308 is exposed. The developer can be a positive-tone developer or a negative-tone developer. Accordingly, a patterned photoresist layer 310P is formed.

[0043] Subsequently, the mask layer 308 is etched, as Figure 3C shown. The mask layer 308 is etched using dry etching, wet etching, or a combination thereof, using the patterned photoresist layer 310P as an etching mask and stopping at the shielding layer 306. Accordingly, a patterned mask layer 308P is formed such that the circuit pattern is transferred from the patterned photoresist layer 310P to the patterned mask layer.

[0044] Figure 3D Illustrated is the stripping of the patterned photoresist layer 310P once the patterned mask layer 308P is formed. The patterned photoresist layer 310P can be stripped using dry etching, wet etching, laser etching, a combination thereof, or another suitable stripping operation.

[0045] Figure 3E Shown is the subsequent formation of the patterned shielding layer 306P. The formation of the patterned shielding layer 306P is performed by etching the shielding layer 306 using the mask layer 308 as an etching mask. Accordingly, the trench 316 extends through the shielding layer 306 and stops at the phase shift layer 304. Accordingly, the upper surface of the phase shift layer 304 is exposed. In some embodiments, the circuit pattern is transferred to the patterned shielding layer 306P. The etching of the patterned shielding layer 306P can be performed using dry etching, wet etching, or a combination thereof.

[0046] Figure 3FThe illustration shows the removal of the patterned mask layer 308P once the patterned shield layer 306P is formed. The patterned mask layer 308P can be removed using dry etching, wet etching, laser etching, or another suitable stripping operation. After the removal operation, the trenches 318 in the patterned shield layer 306P that correspond to the trenches 316 and represent the circuit pattern remain in place.

[0047] Figure 3G Subsequent patterning of the phase shift layer 304 is shown to form the patterned phase shift layer 304P. Patterning of the phase shift layer 304 is performed by etching the phase shift layer 304 using the patterned shield layer 306P as an etch mask. Thus, the trenches 318 extend through the phase shift layer 304 and stop at the substrate 302. Thus, the upper surface of the substrate 302 is exposed. In some embodiments, the circuit pattern is transferred to the patterned phase shift layer 304P. Dry etching, wet etching, or a combination thereof is used to form the patterned phase shift layer 304P.

[0048] Reference Figure 3H , a second photoresist layer 320 is deposited over the patterned shield layer 306P and the patterned phase shift layer 304P. The second photoresist layer 320 can cover the patterned shield layer 306P and can fill the trenches 318. In some embodiments, the second photoresist layer 320 comprises a photosensitive material and can use the same or different material as the material of the photoresist layer 310.

[0049] Still referring Figure 3I , an exposure operation is performed on the second photoresist layer 320 to transfer a second pattern to the second photoresist layer 320. Thus, the portion 322 corresponding to the second pattern in the second photoresist layer 320 is exposed. An electron beam (e-beam) writer or any other suitable writer for irradiating a selected area of the second photoresist layer 320 can be used to expose the portion 322.

[0050] Reference Figure 3J , a developing operation is performed to remove the exposed portion 322. A recess 324 is formed in the second photoresist layer 320, where the recess 324 reopens the trenches 318 and can partially expose the upper surface of the patterned shield layer 306P. Thus, the patterned second photoresist layer 320P is formed. The developing operation can be performed using a developer that acts as a positive tone developer or a negative tone developer.

[0051] Subsequently, the patterned shield layer 306P is etched to form a second pattern in the additionally patterned shield layer 306F, as Figure 3KAs shown. The patterned shield layer 306P is etched using dry etching, wet etching, or a combination thereof, using the patterned second photoresist layer 320P as an etch mask. Thus, another patterned shield layer 306F is formed. Grooves 326 corresponding to the grooves 318 are formed in the patterned phase shift layer 304P. During the patterning operation of the additional patterned shield layer 306F, the patterned phase shift layer 304P remains substantially intact.

[0052] Figure 3L Illustrated is the stripping of the patterned second photoresist layer 320P after the formation of the additional patterned shield layer 306F. The patterned second photoresist layer 320P can be stripped using dry etching, wet etching, laser etching, or another suitable stripping operation. In some embodiments, the second pattern in the patterned phase shift layer 304P increases the sharpness of the image of the additional patterned shield layer 306F that will be projected onto the reticle 108.

[0053] As previously discussed, the reticle cassette 10 including the cover 120 having the window 114 enables the reticle manufacturer to perform early detection at any intermediate stage of the manufacturing process, where the reticle cassette 10 is removed from the manufacturing tool and subjected to an inspection operation, where the reticle 108 is kept sealed within the reticle cassette 10. Since it is not necessary to remove the reticle 108 from the reticle cassette 10 and expose the reticle 108 to the atmospheric pressure environment of the inspection operation, the possibility of contamination is reduced. In addition, reticle defects can be detected and repaired at an earlier stage.

[0054] Figures 4A to 4E is a schematic cross-sectional view of an intermediate stage of a method of repairing a reticle 108 according to some embodiments. Figure 4A Shows a schematic cross-sectional view of the reticle 108 immediately after the development operation for forming the patterned photoresist layer 310P of reference Figure 3B An extraneous particle P above the left groove 314 is detected during the inspection operation. The inspection can be performed across the upper surface of the reticle 108 and Figure 4A is shown for illustrative purposes. This detected particle P may imply that the processing tool having the processing chamber for performing the development operation or a previous operation is contaminated. A cleaning operation may be required before the processing tool operates on the lower reticle. The cleaning operation can include a flushing step using a flushing gas pulse including an inert gas (such as nitrogen (N 2 ), helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), or radon (Rn)). In some embodiments, the cleaning operation includes evacuating the processing chamber to remove unreacted oxygen-containing gases, unreacted metal-containing gases, and any by-products from the processing chamber. Early detection of the contaminated location helps to accurately identify the contaminated processing tool in the processing system and thus saves time and cost.

[0055] Figure 4B The diagram illustrates a schematic cross-sectional view of the photomask 108 immediately after the patterning operation of the mask layer 308 following reference Figure 3C . Particles P were not detected or cleared prior to the patterning of the mask layer 308. Accordingly, the etchant for the patterning operation is blocked by the particles P and cannot reach the left trench 314. Thus, a defective patterned mask layer 308D is formed. Figure 4C The diagram illustrates a schematic cross-sectional view of the photomask 108 immediately after the stripping operation of the patterned photoresist layer 310P following reference Figure 3D . The left trench 316 that would have been formed in a contamination-free patterning operation is missing due to the particles P and instead an excess portion 316M of the defective patterned mask layer 308D is present.

[0056] Figure 4D The diagram illustrates a schematic repair operation according to some embodiments. A repair radiation beam RB, which can be a laser beam or an electron beam (e-beam), is used to remove or etch the excess portion 316M of the defective patterned mask layer 308D. The power and radiation pattern of the radiation beam RB can be appropriately controlled to suit the geometry of the portion 316M without adversely affecting the remainder of the defective patterned mask layer 308D. In some embodiments, an etch gas RG is introduced during the repair operation. The etch gas aids in removing the excess portion 316M and in applying the radiation beam RB. In some embodiments, the etch gas RG for the defective patterned mask layer 308D can include a fluorine-based gas (e.g., F 2 , CF 4 , SF 6 , SnF 4 , XeF 2 ) or another suitable gas (e.g., I 2 ).

[0057] Figure 4E Shows a schematic cross-sectional view of the repaired photomask 108 according to some embodiments. As Figure 4E shown, the circuit pattern of the patterned mask layer 308P is correctly restored to match the circuit pattern of the successfully fabricated photomask 108 as Figure 3D shown.

[0058] Figures 5A to 5E is a schematic cross-sectional view of an intermediate stage of a method for repairing the photomask 108 according to some embodiments. Figure 5A Shows immediately following reference Figure 3BSchematic cross-sectional view of the photomask 108 after the development operation for forming the patterned photoresist layer 310P. A defective patterned photoresist layer 310D is detected, where part 310M (referred to as the intrusion part) is erroneously removed during the development operation. This may imply that the design (e.g., the prescription parameters of the operations for forming the patterned photoresist layer 310P) contains an error, or the material of the photoresist layer 310 has degraded. In some embodiments, a material reconstruction operation may be performed to repair part 310M. Early detection of the location of the defective part helps accurately identify the problematic design during the processing procedure. The material reconstruction operation may be introduced in the current or subsequent steps by considering the processing time and cost of each option. In some embodiments, the defective patterned photoresist layer 310D is stripped during the repair operation. Subsequently, a series of deposition, exposure, and development operations are reapplied to form a defect-free patterned photoresist layer 310P above the mask layer 308, and the manufacturing procedure continues with reference to Figure 3C the steps.

[0059] Figure 5B Illustrates a schematic cross-sectional view of the photomask 108 immediately after the patterning operation of the patterned mask layer 308P with reference to Figure 3C In some embodiments, the defective patterned photoresist layer 310D is not repaired before the patterning of the mask layer 308. Therefore, in addition to forming the trench 314, the etchant used to pattern the mask layer 308 also etches part 308M due to the absence of part 310M. Thus, a defective patterned mask layer 308D is formed. Figure 5C Illustrates a schematic cross-sectional view of the photomask 108 immediately after the stripping operation of the patterned photoresist layer 310P with reference to Figure 3D Part 308M that would originally be formed in place during a defect-free patterning operation is missing.

[0060] Figure 5D Illustrates a schematic repair operation according to some embodiments. A repair radiation beam RB, which can be a laser beam or an electron beam (e-beam), is used to reconstruct part 308M of the defective patterned mask layer 308D. The power and radiation pattern of the radiation beam RB can be appropriately controlled to suit the geometry of part 308M without adversely affecting the rest of the defective patterned mask layer 308D or the underlying shielding layer 306. In some embodiments, a reactive gas RG is introduced during the repair operation. The reactive gas RG helps form part 308M and apply the radiation beam RB. In some embodiments, the reactive gas RG for the defective patterned mask layer 308D may include a silicon-based material, such as (CH 3 O) 4 Si, (C 2 H5 O) 4 Si, (CH 4 SiO) 4 , (CH 4 SiO) 5 or another suitable material.

[0061] Figure 5E Shows a schematic cross - sectional view of the repaired photomask 108 according to some embodiments. As Figure 5E shown, the circuit pattern of the patterned mask layer 308P is correctly restored to match the Figure 3D circuit pattern of the successfully fabricated photomask 108.

[0062] Figures 6A to 6E is a schematic cross - sectional view of an intermediate stage of a method for repairing the photomask 108 according to some embodiments. Figures 6A to 6E The method illustrated in Figures 5A to 5E solves a detection scenario similar to the detection scenario illustrated in Figure 6A but uses a different method. Figure 5C Shows a schematic cross - sectional view of the photomask 108 similar to the photomask shown in

[0063] Figure 6B where a defective patterned mask layer 308D is detected. Part 310M that should have been present is erroneously removed during the development operation. Figure 3E illustrates a schematic cross - sectional view of the photomask 108 immediately after the patterning operation of the shielding layer 306 with reference to Figure 6C In some embodiments, the defective patterned photoresist layer 310D and the defective patterned mask layer 308D are not repaired before the patterning of the shielding layer 306. Thus, in addition to forming the trench 318, the etchant used to pattern the shielding layer 306 also erroneously etches part 306M due to the absence of parts 310M and 308M as etch masks. Thus, a defective patterned shielding layer 306D is formed. Figure 3F illustrates a schematic cross - sectional view of the photomask 108 immediately after the stripping operation of the patterned mask layer 308P with reference to

[0064] Figure 6DFIG. illustrates a schematic repair operation according to some embodiments. A repair radiation beam RB, which can be a laser beam or an electron beam (e-beam), is used to reconstruct a portion 306M of a defective patterned mask layer 306D. The power and radiation pattern of the radiation beam RB can be appropriately controlled to suit the geometry of the portion 306M without adversely affecting the remaining portion of the defective patterned mask layer 306D or the underlying phase shift layer 304. In some embodiments, a reactive gas RG is introduced during the repair operation. The reactive gas RG helps to form the portion 306M and to apply the radiation beam RB. In some embodiments, the reactive gas RG for the patterned mask layer 306P can include chlorine-based gases such as Cl 2 , SnCl 4 , NOCl, NO 2 Cl, CCl 4 or another suitable gas.

[0065] Figure 6E FIG. shows a schematic cross-sectional view of a repaired photomask 108 according to some embodiments. As shown in Figure 6E , the circuit pattern of the patterned mask layer 306P is correctly restored to match the circuit pattern of the successfully fabricated photomask 108 in Figure 3F .

[0066] Figure 7 FIG. is a flowchart of a method 70 of manufacturing a photomask according to some embodiments. It should be understood that additional operations can be provided before, during, and after the steps in Figure 7 , and some of the operations described below can be replaced or eliminated for additional embodiments of the method 70. The order of the operations can be interchangeable. In addition, the same or similar configurations, structures, materials, operations, or processes of the foregoing embodiments can be used in this embodiment and detailed explanations can be omitted.

[0067] At step 702, a photomask cassette is transported to a processing tool and the photomask is removed from the photomask cassette. At step 704, a first operation is performed on the photomask to form a pattern on the photomask. In some embodiments, the first operation can include one or more of the operations illustrated in Figures 3A to 3L , and can include exposure, development, baking, etching, stripping, or other semiconductor processing operations.

[0068] At step 706, the photomask is stored in the photomask cassette and the photomask cassette is transported to an inspection tool. At step 708, an inspection operation is performed on the photomask through a window of the photomask cassette. The material and configuration of the window are described with reference to the window 114 in Figure 1 and 2B .

[0069] At step 710, it is determined whether any defects are found during the inspection operation. If so, then method 70 proceeds to step 712 to determine the type of defect. If it is determined at step 710 that no defects are found in the photomask, then the method loops back to step 704 to perform subsequent manufacturing steps until the photomask is completed.

[0070] At step 712, it is determined whether the type of defect is a contamination type or a design type. If it is determined that the detected defect is classified as a contamination type, then method 70 proceeds to step 714, where the processing tool is powered down and a cleaning operation is performed on the processing tool to clean foreign particles, dust, or unreacted gases. If no further contamination is found, then the processing tool starts operating again.

[0071] Subsequently, at step 716, a second operation is performed on the photomask to repair the defect. During step 716, the photomask cassette is transported to the processing chamber and the photomask is removed from the photomask cassette, after which a second operation is performed to repair the defect. The second operation may include removing an excessive portion or reconstructing a missing portion of one or more layers in the photomask.

[0072] In some embodiments, method 70 accesses a library of photomask patterns to determine the type of defect. The library stores associations between several photomask patterns and the identified causes of the defects. As previously discussed, the defects may be caused by contamination or design errors. Additionally, defective photomask patterns resulting from contamination or design errors may have a specific appearance. Given the acquired pattern image of a photomask, the library may assist in identifying which type of design error, such as bridges, intrusions, and protrusions. The library may improve the efficiency and accuracy of the cause based on the inspection image of the photomask.

[0073] In some embodiments, method 70 proceeds to step 708 to inspect the photomask after the repair operation at step 716. Method 70 may loop through steps 708, 710, 712, 714, and 716 until no defects are found in the repaired photomask.

[0074] If it is determined at step 712 that the detected defect is classified as a design type, then method 70 proceeds to step 716 to perform a second operation. At step 718, it is determined whether the fabrication of the photomask is completed. If so, then method 70 ends. If one or more operations are required, then method 70 loops back to step 704 to perform another first operation until the photomask is completed.

[0075] Figure 8is a flowchart of a method 80 of manufacturing a semiconductor device. A photomask 108 fabricated, inspected, repaired, and operated in association with the photomask cassette 10 as described in the preceding paragraphs may be used to manufacture the semiconductor device. The photomask 108 used in method 80 is considered to be complete and no defects are found therein. It should be understood that additional operations may be provided before, during, and after the steps in Figure 8 and some of the operations described below may be replaced or eliminated for additional embodiments of method 80. The order of operations may be interchangeable. In addition, the same or similar configurations, structures, materials, operations, or processes of the foregoing embodiments may be used in this embodiment and detailed explanations may be omitted.

[0076] Method 80 begins at step 802, where a workpiece, such as a semiconductor substrate having a material layer, is provided. The semiconductor substrate comprises a semiconductor material, such as silicon. In some embodiments, the semiconductor substrate may comprise other semiconductor materials, such as silicon germanium, silicon carbide, gallium arsenide, and the like. Alternatively, the semiconductor substrate comprises another elemental semiconductor, such as germanium; a compound semiconductor, comprising silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, and / or indium antimonide; an alloy semiconductor, comprising SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and / or GaInAsP; or a combination thereof. In some embodiments, the semiconductor substrate comprises a doped region, such as a p-type doped region or an n-type doped region.

[0077] In some embodiments, the material layer of the semiconductor substrate may be a semiconductor layer, a dielectric layer, or a conductive layer. In some embodiments, the material layer may be embedded in the semiconductor substrate or deposited over the semiconductor substrate. The material layer may be formed of a single layer or may comprise a multi-layer structure.

[0078] At step 804, a photoresist layer is formed over the material layer. The photoresist layer may be formed over the material layer by CVD, PVD, ALD, spin coating, or another suitable film-forming method. Next, method 80 continues with step 806, where a photomask (such as the photomask 108 described above) is used in a lithography operation to pattern the photoresist layer. In an embodiment, the photomask may be placed on the mask stage of a lithography system and the semiconductor substrate may be placed on the wafer stage. The lithography operation may involve projecting exposure radiation onto the photoresist layer via transmission or reflection onto the photomask. Portions of the photoresist layer may be removed after the lithography operation.

[0079] Method 80 continues with step 808 to pattern the material layer using the patterned photoresist layer as an etch mask. Next, the photoresist layer is removed. The removal operation may comprise an etching or ashing operation.

[0080] According to an embodiment, a photomask cassette includes: a base configured to support a photomask; and a cover configured to form a sealed space with the base. The cover includes a window having a window body and transparent films on both sides of the window body. The window is configured to allow radiation of a predetermined wavelength to pass through with a transmittance greater than 70%.

[0081] According to an embodiment, a photomask cassette includes: a base configured to support a photomask; and a cover detachably coupled to the base. The cover includes a window that allows radiation having a wavelength between about 400 nm and about 700 nm to pass through with a transmittance greater than 70%.

[0082] According to an embodiment, a method of manufacturing a photomask includes: performing a first operation to form a pattern on the photomask; placing the photomask in a photomask cassette including a base and a cover configured to form a sealed space with the base, and the cover including a window configured to allow radiation of a predetermined wavelength to pass through; and performing an inspection operation on the photomask through the window.

[0083] The foregoing outlines the components of several embodiments such that those skilled in the art may better understand aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for implementing the same purposes and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also recognize that these equivalent constructs do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made herein without departing from the spirit and scope of the present disclosure.

[0084]

Symbol Description

[0085] 10: Photomask Cassette / Sealed Photomask Cassette

[0086] 70: Method

[0087] 80: Method

[0088] 102: Platform

[0089] 104: Photomask Holder

[0090] 104R: Groove

[0091] 106: Latch

[0092] 108: Photomask / Transmission-Type Photomask / Repaired Photomask

[0093] 110: Base

[0094] 112: Frame

[0095] 114: Window

[0096] 116: Form

[0097] 117: Support beam

[0098] 118A: Membrane

[0099] 118B: Membrane

[0100] 120: Cover

[0101] 120C: Central part

[0102] 120P: Peripheral part

[0103] 302: Substrate

[0104] 304: Phase shift layer / underlying phase shift layer

[0105] 304P: Patterned phase shift layer

[0106] 306: Masking layer / underlying masking layer

[0107] 306D: Defective patterned masking layer

[0108] 306F: Additional patterned masking layer

[0109] 306M: Portion

[0110] 306P: Patterned masking layer

[0111] 308: Mask layer

[0112] 308D: Defective patterned mask layer

[0113] 308M: Portion

[0114] 308P: Patterned mask layer

[0115] 310: Photoresist layer / positive tone photoresist layer

[0116] 310D: Defective patterned photoresist layer

[0117] 310M: Portion

[0118] 310P: Patterned photoresist layer / non-defective patterned photoresist layer

[0119] 312: Portion

[0120] 314: Trench / left trench

[0121] 316: Trench / left trench

[0122] 316M: Excess portion / portion

[0123] 318: Groove

[0124] 320: Second photoresist layer

[0125] 320P: Patterned second photoresist layer

[0126] 322: Portion / Exposed portion

[0127] 324: Recess

[0128] 326: Groove

[0129] 702: Step

[0130] 704: Step

[0131] 706: Step

[0132] 708: Step

[0133] 710: Step

[0134] 712: Step

[0135] 714: Step

[0136] 716: Step

[0137] 718: Step

[0138] 802: Step

[0139] 804: Step

[0140] 806: Step

[0141] 808: Step

[0142] AA: Cross-section line

[0143] P: Foreign particle / Detected particle / Particle

[0144] T: Deposition thickness

Claims

1. A method of manufacturing a photomask, which includes: providing a photomask, the photomask including a substrate, a phase shift layer, a shielding layer, a mask layer, and a photoresist layer located above a previous layer; performing a first operation, wherein the first operation includes etching the mask layer to form a patterned mask layer; placing the photomask including the substrate, the phase shift layer, the shielding layer, and the patterned mask layer in a photomask cassette, the photomask cassette including a base and a cover configured to form a sealed space with the base, and the cover including a window configured to allow radiation at a predetermined wavelength to pass through; performing a first inspection operation on the patterned mask layer through the window, wherein the first inspection operation includes inspecting whether the patterned mask layer has defects; and performing the following operations to complete the photomask: etching the shielding layer through the patterned mask layer in response to no defects being found to form a patterned shielding layer; and performing a lithography operation to transfer the pattern on the patterned shielding layer to a workpiece.

2. The method according to claim 1, further comprising performing the following operations in response to defects being found during the first inspection operation: repairing the patterned mask layer.

3. The method according to claim 1, wherein performing the first inspection operation includes emitting inspection radiation to pass through the window and receiving the reflected radiation from the photomask.

4. The method according to claim 3, wherein the inspection radiation includes a wavelength between 400 nm and 700 nm.

5. The method according to claim 1, wherein the window includes a window body and transparent films located on both sides of the window body.

6. The method according to claim 1, further includes: performing an exposure operation and a development operation on the photoresist layer before the first operation to form a patterned photoresist layer; placing the photomask including the substrate, the phase shift layer, the shielding layer, the mask layer, and the patterned photoresist layer in the photomask cassette; performing a second inspection operation on the patterned photoresist layer through the window, wherein the second inspection operation includes inspecting whether the patterned photoresist layer has defects; transporting the photomask from the photomask cassette to a semiconductor tool after the second inspection operation; and removing the foreign particles from the patterned photoresist layer in response to foreign particles being detected during the second inspection operation.

7. The method according to claim 6, further comprising, after the removal of the foreign particles, using the patterned photoresist layer as an etching mask to etch the mask layer.

8. The method according to claim 6, further comprising cleaning the processing tool that performs the development operation before the patterning operation in response to the foreign particles being detected.

9. The method according to claim 6, further includes: transporting the photomask from the photomask cassette to a semiconductor tool after the first inspection operation; and Repair the defective portion in response to detecting a defective portion of the patterned mask layer during the first inspection operation.

10. The method according to claim 9, further comprising performing a patterning operation on the shielding layer using the patterned mask layer as an etch mask after the repair of the defective portion.

11. A method of manufacturing a photomask, which comprises: providing a photomask, the photomask including a substrate, a phase shift layer, a shielding layer, a mask layer, and a photoresist layer located above a previous layer; performing a first operation in a first processing tool, wherein the first operation includes etching the mask layer and forming a patterned mask layer; moving the photomask including the substrate, the phase shift layer, the shielding layer, and the patterned mask layer to a photomask cassette, the photomask cassette including a window configured to allow radiation at a predetermined wavelength to pass through; performing an inspection operation on the patterned mask layer through the window, wherein the inspection operation includes inspecting whether the patterned mask layer is defective; removing the photomask from the photomask cassette in a second processing tool; determining whether to perform a cleaning or repair operation in response to the result of the inspection operation; and performing the following operations to complete the photomask: etching the shielding layer through the patterned mask layer in response to no defect being found to form a patterned shielding layer; and performing a lithography operation to transfer the pattern on the patterned shielding layer to a workpiece.

12. The method according to claim 11, wherein the radiation has a wavelength such that it does not react with the photoresist layer of the photomask.

13. The method according to claim 12, wherein the wavelength is in the range between 400 nm and 700 nm.

14. The method according to claim 11, wherein the window includes a window body and transparent films located on both sides of the window body.

15. The method according to claim 14, wherein the transparent film includes at least one of aluminum zinc oxide (AZO), indium tungsten oxide (ITO), fluorine-doped tin oxide (FTO), and carbon nanotubes.

16. The method according to claim 14, wherein the transparent film has a thickness between 20 nm and 200 nm.

17. The method according to claim 14, wherein the photomask cassette includes a cover, the cover comprising an opaque material that laterally surrounds the window.

18. A method of manufacturing a photomask, which comprises: providing a photomask, the photomask including a substrate, a phase shift layer, a shielding layer, and a mask layer located above a previous layer; performing a first operation in a first processing tool, wherein the first operation includes etching the mask layer and forming a patterned mask layer; moving the photomask including the substrate, the phase shift layer, the shielding layer, and the patterned mask layer to a photomask cassette, the photomask cassette including a window and films coated on both sides of the window; performing an inspection operation on the patterned mask layer through the window, wherein the inspection operation includes inspecting whether the patterned mask layer is defective; Remove the mask from the mask cassette in a second processing tool; Perform a repair operation or a cleaning operation in response to determining that a defect is found during the inspection operation; and Perform the following operations to complete the mask: Etch the shielding layer through the patterned mask layer in response to no defect being found to form a patterned shielding layer; and Perform a photolithography operation to transfer the pattern on the patterned shielding layer to a workpiece.

19. The method according to claim 18, wherein the mask is held in the mask cassette during the inspection operation.

20. The method according to claim 18, wherein the film has a transmittance greater than 65% of the inspection radiation used in the inspection operation.

21. A method of manufacturing a mask, which comprises: Providing a mask, the mask including a substrate, a phase shift layer, a shielding layer, a mask layer, and a patterned photoresist layer located above a previous layer; Placing the mask in a mask cassette, the mask cassette forming a sealed space to accommodate the mask, and the mask cassette including a window disposed on an upper surface of the mask cassette and configured to allow radiation at a predetermined wavelength to pass through; Performing a first inspection operation on the patterned photoresist layer through the window, wherein the first inspection operation includes inspecting whether a defect occurs in the patterned photoresist layer; Performing a first operation through the patterned photoresist layer as an etch mask in response to no defect being found during the first inspection operation, wherein the first operation includes etching the mask layer to form a patterned mask layer; and Perform the following operations to complete the mask: Etch the shielding layer through the patterned mask layer in response to no defect being found to form a patterned shielding layer; and Perform a photolithography operation to transfer the pattern on the patterned shielding layer to a workpiece.

22. The method according to claim 21, which further comprises: Placing the mask including the substrate, the phase shift layer, the shielding layer, and the patterned mask layer in the mask cassette; and Performing a second inspection operation on the patterned mask layer through the window, wherein the second inspection operation includes inspecting whether a defect occurs in the patterned mask layer.

23. The method according to claim 22, which further comprises repairing the pattern on the patterned mask layer in response to a defect being found during the second inspection operation.

24. The method according to claim 22, wherein the window includes a window body and transparent films located on both sides of the window body.

25. The method according to claim 22, further comprises: Transporting the mask from the mask cassette to a semiconductor tool after the first inspection operation; and Causing the foreign particle to be removed from the patterned photoresist layer in response to a foreign particle being detected during the first inspection operation.

26. The method according to claim 25, which further comprises, after the removal of the foreign particle, using the patterned photoresist layer as an etch mask to etch the mask layer.

27. The method according to claim 25, further comprising cleaning a processing tool for forming the patterned photoresist layer prior to the patterning operation in response to detecting the foreign particle.

28. The method according to claim 22, further comprising: transporting the photomask from the photomask cassette to a semiconductor tool after the second inspection operation; and repairing a defective portion of the patterned mask layer in response to detecting the defective portion during the second inspection operation.

29. The method according to claim 28, further comprising performing a patterning operation using the patterned mask layer as an etch mask after the repair of the defective portion.

30. The method according to claim 21, wherein performing the first inspection operation includes emitting inspection radiation to pass through the window and receiving reflected radiation from the photomask.

31. A method of manufacturing a photomask, which comprises: providing a photomask including a substrate, a phase shift layer, a shielding layer, a mask layer, and a photoresist layer located above a previous layer; performing a first operation in a first processing tool, wherein the first operation includes etching the mask layer and forming a patterned mask layer; moving the photomask including the substrate, the phase shift layer, the shielding layer, and the patterned mask layer to a photomask cassette; performing an inspection operation on the patterned mask layer by transmitting radiation through a transparent window of the photomask cassette, wherein the inspection operation includes inspecting whether the patterned mask layer has defects; determining whether to perform a cleaning or repair operation in response to the result of the inspection operation; and performing the following operations to complete the photomask: etching the shielding layer through the patterned mask layer in response to no defects being found to form a patterned shielding layer; and performing a lithography operation to transfer the pattern on the patterned shielding layer to a workpiece.

32. The method according to claim 31, wherein the radiation has a certain wavelength so as not to react with the photoresist layer.

33. The method according to claim 32, wherein the wavelength is in the range between 400 nm and 700 nm.

34. The method according to claim 31, wherein the transparent window includes a window body and transparent films located on both sides of the window body.

35. The method according to claim 34, wherein the transparent film includes at least one of aluminum zinc oxide (AZO), indium tungsten oxide (ITO), fluorine-doped tin oxide (FTO), and carbon nanotubes.

36. The method according to claim 34, wherein the transparent film has a thickness between 20 nm and 200 nm.

37. The method according to claim 34, wherein the photomask cassette includes a cover, and the cover includes an opaque material that laterally surrounds the transparent window.

38. A method of manufacturing a photomask, which comprises: providing a photomask including a substrate, a phase shift layer, a shielding layer, and a mask layer located above a previous layer; performing a first operation in a first processing tool, wherein the first operation includes etching the mask layer and forming a patterned mask layer; Move the photomask including the substrate, the phase shift layer, the shielding layer, and the patterned mask layer to a photomask cassette, the photomask cassette including a window through which the pattern is visible; Perform an inspection operation on the patterned mask layer through the window, wherein the inspection operation includes inspecting whether the patterned mask layer has defects; Perform a repair operation or a cleaning operation in response to determining that a defect is found during the inspection operation; and Perform the following operations to complete the photomask: Etch the shielding layer through the patterned mask layer in response to no defects being found to form a patterned shielding layer; and Perform a photolithography operation by transferring the pattern on the patterned shielding layer to a workpiece.

39. The method according to claim 38, wherein the photomask is held within the photomask cassette during the inspection operation.

40. The method according to claim 38, wherein the window further includes films on both sides of the window, wherein the films have a transmittance greater than 65% of the inspection radiation used in the inspection operation.

Images