Method and system for cleaning the surface of a photomask

Abstract

A method and system for cleaning a surface of a photomask includes retrieving a photomask from a photomask library and transferring the photomask to a first exposure device. The surface of the photomask is cleaned by irradiating the surface of the photomask with extreme ultraviolet radiation for a predetermined irradiation time in the first exposure device. After cleaning the surface of the photomask, the photomask is transferred to a second exposure device for a lithography operation.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a method, and particularly, to a method and system for cleaning a surface of a reticle. BACKGROUND

[0002] During integrated circuit (IC) design, multiple patterns of an integrated circuit are generated on a substrate for different steps of an integrated circuit fabrication process. The multiple patterns can be generated by projecting (e.g., imaging) multiple layout patterns of a mask on a photoresist layer of a wafer. Lithography processes transfer the multiple layout patterns of a mask to a photoresist layer of a wafer so that etching, implantation, or other steps are applied only to predefined areas of a wafer. Generally, a reticle (e.g., a mask) is stored in a reticle library under vacuum conditions when not in use. SUMMARY

[0003] Embodiments of the present disclosure aim to provide a method for cleaning a surface of a reticle, comprising: retrieving a reticle from a reticle library; transferring the reticle to a first exposure device; cleaning a surface of the reticle in the first exposure device by irradiating the surface of the reticle with a first extreme ultraviolet radiation for a predetermined irradiation time; and after cleaning the surface of the reticle, transferring the reticle to a second exposure device for a lithography operation.

[0004] Embodiments of the present disclosure aim to provide another method for cleaning a surface of a reticle, comprising: cleaning a surface of the reticle in a first exposure device by irradiating the surface of the reticle with an extreme ultraviolet radiation of a first extreme ultraviolet light source for an irradiation time; after cleaning the surface of the reticle, transferring the reticle from the first exposure device to a second exposure device for a lithography operation; and projecting layout patterns of the reticle onto a photoresist layer of a wafer in the second exposure device using an extreme ultraviolet radiation of a second extreme ultraviolet light source.

[0005] Embodiments of the present disclosure are directed to another system for cleaning a surface of a photomask, comprising: a main controller, an analyzer module coupled to the main controller, a rapid exchange device having an extendable robot arm, a first exposure device, and a second exposure device. The first exposure device comprises a first photomask stage and a first extreme ultraviolet light source. The first photomask stage is configured to hold a photomask. The second exposure device comprises a second photomask stage, a second extreme ultraviolet light source, a stage, and an optical system. The stage is configured to hold a wafer. The main controller is configured to command the first extreme ultraviolet light source to turn on, the first extreme ultraviolet light source turning on to irradiate extreme ultraviolet radiation from the first extreme ultraviolet light source, and the first extreme ultraviolet light source turning on to irradiate a surface of the photomask in the first photomask stage of the first exposure device with the extreme ultraviolet radiation of the first extreme ultraviolet light source for a predetermined irradiation time to clean the surface of the photomask. After cleaning the surface of the photomask, the main controller is configured to command the rapid exchange device to transfer the photomask from the first exposure device to the second photomask stage of the second exposure device for a lithography operation by the extendable robot arm. After transferring the photomask from the first exposure device to the second photomask stage of the second exposure device, the main controller is configured to command the second extreme ultraviolet light source to turn on, the second extreme ultraviolet light source turning on to irradiate extreme ultraviolet radiation from the second extreme ultraviolet light source, and the second extreme ultraviolet light source turning on to project a layout of the photomask onto a photoresist layer of the wafer through the optical system. BRIEF DESCRIPTION OF DRAWINGS

[0006] The various features illustrated are set forth in detail in the following detailed description and accompanying drawings. Note that the relative dimensions of the various features can have been exaggerated or reduced for the sake of discussion. Embodiments of the present disclosure will be described with reference to the accompanying drawings, of which:

[0007] Figure 1 A process flow for creating a photoresist pattern on a semiconductor substrate;

[0008] Figure 2 A rapid exchange device for transferring a photomask between different locations;

[0009] Figure 3 A process flow for creating a photoresist pattern on a semiconductor substrate according to some embodiments of the present disclosure;

[0010] Figure 4 A schematic diagram of an exposure device for creating a photoresist pattern on a wafer;

[0011] Figures 5A-5B A cross-sectional view of a reflective photomask structure and projecting the reflective photomask structure on a semiconductor device in an exposure device;

[0012] Figure 6 An inspection system for a photoresist pattern disposed on a semiconductor substrate;

[0013] Figures 7A-7FAn exposure apparatus for measuring reflected projection light from a reflective mask according to some embodiments of the present disclosure;

[0014] Figure 8 A control system for cleaning a mask and for projecting a layout pattern of the cleaned mask on a semiconductor substrate according to some embodiments of the present disclosure;

[0015] Figure 9 A flowchart of an exemplary process for cleaning a mask and for projecting a layout pattern of the cleaned mask on a semiconductor substrate according to some embodiments of the present disclosure;

[0016] Figures 10A-10B An apparatus for cleaning a mask and for projecting a layout pattern of the cleaned mask on a semiconductor substrate according to some embodiments of the present disclosure.

[0017] NOTATION

[0018] 10: semiconductor substrate

[0019] 15: photoresist layer

[0020] 29: radiation

[0021] 30: substrate

[0022] 34: semiconductor device

[0023] 35: reflective layer

[0024] 37, 39: thin film

[0025] 40: cover layer

[0026] 45: absorption layer

[0027] 50: radiation beam

[0028] 50': reflected beam

[0029] 55: layout pattern

[0030] 80: mask

[0031] 100: radiation source

[0032] 102: photoresist coating operation

[0033] 104: post-applied bake (PAB) operation

[0034] 105: mask retrieval operation

[0035] 106: mask loading and cleaning operation

[0036] 108: mask loading and exposure operation

[0037] 110: post-exposure bake (PEB) operation

[0038] 112: developing operation

[0039] 150, 300: process flow

[0040] 200: rapid exchange device (RED)

[0041] 202: reticle library

[0042] 204: first movable section

[0043] 205: first pivot point

[0044] 205a, 205b: optical elements

[0045] 205c: reflective mask

[0046] 205d, 205e: reduction projection optical elements

[0047] 206: robotic device

[0048] 208: second movable section

[0049] 210: target semiconductor substrate

[0050] 212: first exposure device

[0051] 214: second exposure device

[0052] 240: rapid exchange device (RED) controller

[0053] 302: line

[0054] 400: exposure device

[0055] 406: vacuum pressure controller

[0056] 408: pressure sensor

[0057] 500: cross-sectional view

[0058] 550: exposure configuration

[0059] 560, 660: stage

[0060] 565, 665: stage controller

[0061] 600: inspection system

[0062] 617: uniform beam

[0063] 619: focused beam

[0064] 630, 830: analyzer module

[0065] 633: image processing unit

[0066] 634: lens

[0067] 635: scanning imaging device

[0068] 702: particle

[0069] 704: contaminant layer

[0070] 705: light source

[0071] 706: surface

[0072] 710: image detector system

[0073] 732: coordinate

[0074] 734: time coordinate

[0075] 738: curve

[0076] 800: control system

[0077] 814: neural network module

[0078] 816: machine learning module

[0079] 818: data mining module

[0080] 840: main controller

[0081] 900: process

[0082] 1000: computer system

[0083] 1001: computer

[0084] 1002: keyboard

[0085] 1003: mouse

[0086] 1004: screen display

[0087] 1005: optical disk drive

[0088] 1006: magnetic disk drive

[0089] 1011: microprocessing unit

[0090] 1012: read only memory

[0091] 1013: random access memory

[0092] 1014: hard disk

[0093] 1015: bus

[0094] 1021: optical disc

[0095] 1022: magnetic disc

[0096] A: angle

[0097] S1: horizontal

[0098] S910, S920, S930, S940: operation

[0099] T1: time DETAILED DESCRIPTION

[0100] The following detailed description is presented to provide a thorough understanding of various embodiments of the application. Numbered items of construction and arrangement are presented in a specific example in the following description to simplify the present disclosure. Of course, these are merely examples and are not intended to limit the present disclosure. For example, in the description, a first feature is formed over or on a second feature, which can include embodiments where the first feature is formed in direct contact with the second feature, and can also include embodiments where additional features can be formed between the first feature and the second feature such that the first feature can not be in direct contact with the second feature. Furthermore, the present disclosure can make reference to a number of examples and / or drawings in various places throughout this application. These are provided merely to further clarify the present disclosure. The repeated use of the reference numerals in the specification and drawings is intended to represent the same, or similar, objects unless otherwise indicated.

[0101] Furthermore, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", and the like, can be used herein for ease of describing one element or feature to another, as illustrated in the drawings. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the drawings. The devices can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Furthermore, the term "comprising" is used herein to mean including, but not limited to, the elements or features that follow the term. The term "consisting of" is used herein to mean including, but not limited to, the elements or features that follow the term, and excluding additional elements or features. The term "one or more of" followed by a list of elements or features is used herein to mean one, some, or all of the elements or features in the list. The term "at least one of" followed by a list of elements or features is used herein to mean one, some, or all of the elements or features in the list.

[0102] In some embodiments, reticles are stored in a reticle library, and the reticle library is maintained under vacuum conditions to avoid deposition of particles and hydrocarbon contamination on the reticles. However, particles and hydrocarbon contamination can build up on the reticles when the reticles are used during the lithography process. The particles and hydrocarbon contamination can damage the critical dimension (CD) uniformity in the patterns produced on the photoresist layer of the wafer. In some embodiments, the reticles are cleaned with a solvent to clean the particles and hydrocarbon contamination from the surface of the reticles after the reticles are retrieved from the reticle library. In some embodiments, the reticles are cleaned with a solvent to clean the particles and hydrocarbon contamination from the surface of the reticles before the reticles are stored in the reticle library. If the reticles are cleaned before the reticles are stored, cleaning the reticles with a solvent can introduce additional particles in the reticle library. If the reticles are cleaned after the reticles are retrieved from the reticle library, cleaning the reticles with a solvent can introduce additional particles in the exposure device of the lithography system. In addition, cleaning the reticles with a solvent can cause a long delay in the lithography process. Therefore, in some embodiments, the reticles are cleaned offline. The reticles are retrieved from the reticle library, the retrieved reticles are cleaned, and the reticles are stored again in the reticle library.

[0103] When a photomask is retrieved from a photomask library and used in a lithography process, particles and / or hydrocarbon contaminants may accumulate on the photomask, potentially degrading it and causing non-uniformity in the wafer's critical dimension (CD). Therefore, it is desirable to clean the photomask before performing the lithography process. In some embodiments, the lithography system includes two exposure devices. One of the exposure devices projects the photomask onto a photoresist layer on the wafer to pattern the wafer. The other of the two exposure devices has a separate radiation source (e.g., an extreme ultraviolet (EUV) radiation source) and is used to irradiate the surface layer of the photomask. In some embodiments, the energy of the irradiation is used to break down the layer of particles or hydrocarbon contaminants deposited on the surface layer of the photomask. Furthermore, the more the surface layer of the photomask is irradiated, the more the layer of particles or hydrocarbon contaminants is broken down. In some embodiments, the photomask is a reflective reticle; prolonged irradiation of the photomask's surface layer not only delays the lithography process but may also damage the layers of the photomask due to the additional irradiation. Damage to any layer of a photomask (e.g., the reflective layer of a reflective photomask) can compromise the uniformity of the critical dimension (CD). Therefore, it is desirable to irradiate the surface layers of the photomask to reduce or eliminate the impact of particulate and hydrocarbon contaminants on the surface layers without damaging the photomask structure (e.g., the reflective structure). Thus, it is desirable to irradiate the surface layers of the photomask before damaging the structure to achieve optimal improvement in critical dimension uniformity (CDU).

[0104] Figure 1 A process flow 150 for generating photoresist patterns on a semiconductor substrate. In some embodiments, through... Figure 8 The control system 800 and / or Figures 10A-10B A computer system 1000 executes the process flow 150. In the photoresist coating operation 102, a photoresist layer of photoresist material is disposed (e.g., coated) on the top surface of a substrate (e.g., a wafer of a workpiece). Figure 5B As shown, a photoresist layer 15 is disposed on a semiconductor substrate 10. A post-application bake (PAB) operation 104 is performed, and the semiconductor substrate 10 containing the photoresist layer 15 is baked to drive out the solvent in the photoresist material and cure the photoresist layer 15 on the top of the semiconductor substrate 10.

[0105] In embodiments of the present disclosure, the terms "mask," "photomask," and "reticle" are used interchangeably. Also, the terms "resist" and "photo resist" are used interchangeably. At the mask retrieval operation 105, a reticle is retrieved from a reticle library. At the Figure 2 mask retrieval operation 105 is described in more detail in the description of the mask load and exposure operation 108. The retrieved reticle is loaded into an exposure device by a mask load and exposure operation 108, which is described in Figure 4 . The mask load and exposure operation 108 also projects the mask onto the photo resist layer 15 of the semiconductor substrate 10 using actinic radiation from a radiation source. In some embodiments, the layout pattern on the mask is projected onto the photo resist layer 15 by extreme ultraviolet (EUV) radiation from an EUV light source to produce a photo resist pattern in the photo resist layer 15 on the semiconductor substrate 10. At a postexposure bake (PEB) operation 110, a postexposure bake (PEB) is performed on the wafer, in which the photo resist layer is further baked after exposure to the actinic radiation and before development in the development operation 112. The photo resist material of the photo resist layer 15 is developed by applying a developer solution to the photo resist layer. For positive tone photo resist material, at the development operation 112, the exposed areas are developed by applying the developer solution, then the developed areas are removed and the remaining areas produce the photo resist pattern of the photo resist layer 15. For negative tone photo resist material, at the development operation 112, the unexposed areas are developed by applying the developer solution, then the developed areas are removed and the remaining areas produce the photo resist pattern of the photo resist layer 15. The mask is described in Figure 5A .

[0106] Figure 2A rapid exchange device (RED) 200 is provided for transferring reticles between different locations. The rapid exchange device (RED) 200 transfers reticles between a reticle library 202, a first exposure device 212, and a second exposure device 214. The rapid exchange device (RED) 200 includes a robotic device 206 having a robotic arm. The robotic arm includes a first movable section 204 and a second movable section 208. The second movable section 208 rotates about a first pivot point 205. The first movable section 204 rotates about a second pivot point (not shown) within the robotic device 206, and the first movable section 204 also moves the first pivot point and the second movable section. The robotic device 206 can rotate the first movable section 204 and the second movable section 208 about their respective pivot points to extend the robotic arm to the reticle library 202, the first exposure device 212, or the second exposure device 214. In some embodiments, the robotic device 206, the reticle library 202, the first exposure device 212, and the second exposure device 214 are maintained in a vacuum environment.

[0107] The rapid exchange device (RED) 200 also includes a rapid exchange device (RED) controller 240 coupled to the reticle library 202, the robotic device 206, the first exposure device 212, and the second exposure device 214. In some embodiments, the rapid exchange device (RED) controller 240 instructs the robotic device 206 to retrieve a reticle from the reticle library 202 and load the reticle into the first exposure device 212 or the second exposure device 214. In some embodiments, the rapid exchange device (RED) controller 240 instructs the robotic device 206 to retrieve a reticle from the first exposure device 212 or the second exposure device 214 and load the reticle into the other exposure device. In some embodiments, the rapid exchange device (RED) controller 240 instructs the reticle library 202 to release one of the reticles to be retrieved. In some embodiments, the rapid exchange device (RED) controller 240 instructs the robotic device 206 to load a reticle on a mask table of the first exposure device 212 or the second exposure device 214. The first exposure device 212 and the second exposure device 214 are described in Figure 4 、 Figure 5B and Figure 7A .

[0108] Figure 3 A process flow 300 for creating a photoresist pattern on a semiconductor substrate according to some embodiments of the present disclosure is provided. The process flow 300 includes the photoresist coating operation 102, the post-applied bake (PAB) operation 104, the post-exposure bake (PEB) operation 110, and the development operation 112 of the process flow 150. Figure 1 of the process flow 150. In addition, the process flow 300 includes the photoresist coating operation 302, the post-applied bake (PAB) operation 304, the post-exposure bake (PEB) operation 310, and the development operation 312 of the process flow 350. Figure 2the mask retrieval operation 105 performed by the rapid exchange device (RED) 200. At the mask retrieval operation 105, Figure 2 The rapid exchange device (RED) controller 240 commands the robotic device 206 to interact with the reticle library 202. In response to the command from the rapid exchange device (RED) controller 240, the reticle library 202 releases a reticle and the robotic device 206's robotic arm extends into the reticle library 202 to retrieve the released reticle. The process flow 300 also includes a mask load and cleaning operation 106. At the mask load and cleaning operation 106, the rapid exchange device (RED) controller 240 commands the robotic device 206 to load the released reticle in the first exposure device 212. Further, after loading the reticle in the first exposure device 212, the rapid exchange device (RED) controller 240 commands the radiation source (e.g., an extreme ultraviolet (EUV) light source) of the first exposure device 212 to irradiate the surface of the reticle with the radiation of the radiation source for a predetermined amount of time to clean the surface of the reticle. In some embodiments, the radiation source is an extreme ultraviolet (EUV) light source or other light source with a suitable wavelength that can break down layers of hydrocarbon contaminants and particles. In some embodiments, the surface of the reticle is a surface region of the reflective reticle into which the radiation enters. In some embodiments, as at least part of the cleaning operation and to irradiate the surface of the reticle, a dummy wafer is projected with the layout pattern of the reticle. Also, at the mask load and exposure operation 108, the reticle loaded in the first exposure device 212 is transferred to the second exposure device 214 and the radiation source of the second exposure device 214 projects the layout pattern of the reticle on the photoresist layer (e.g., the photoresist layer 15 of the substrate 10) of the substrate to create a photoresist pattern. Figure 5B

[0109] Figure 4 ​A schematic diagram of an exposure apparatus 400 for generating a photoresist pattern on a wafer. The exposure apparatus 400, consistent with the second exposure apparatus 214, illustrates exposure of a substrate coated with photoresist with a patterned beam of radiation 29 from a radiation source 100, such as an extreme ultraviolet (EUV) radiation source. In some embodiments, the exposure apparatus 400 is an integrated circuit lithography tool, such as a stepper, a scanner, a step and scan system, a direct write system, an apparatus using contact and / or proximity masks, etc., such as to provide one or more optical elements 205a, 205b of an optical system, and a beam of EUV light radiation to illuminate a patterned optical element (e.g., a reticle, such as a reflective mask 205c) to generate a patterned beam of the optical system and one or more reduction projection optical elements 205d, 205e for projecting the patterned beam onto a target semiconductor substrate 210. The target semiconductor substrate 210 is consistent with the semiconductor substrate of Figure 5B In some embodiments, a photoresist layer consistent with the photoresist layer 15 of Figure 5B is provided on the target semiconductor substrate 210. A mechanical assembly (not shown) can be provided to generate controlled relative motion between the target semiconductor substrate 210 and the patterned optical element (e.g., the reflective mask 205c). Through the controlled relative motion, different dice of the patterned substrate are generated. In some embodiments, the exposure apparatus 400 is an extreme ultraviolet lithography (EUVL) exposure apparatus. As further shown, Figure 4 The extreme ultraviolet lithography (EUVL) exposure apparatus of Figure 5A also includes an extreme ultraviolet (EUV) radiation source 100 to illuminate the target semiconductor substrate 210. In some embodiments, because gas molecules can absorb EUV light, a lithography system for EUV lithography patterning is in a vacuum environment to avoid EUV intensity loss. In some embodiments, a pressure sensor 408 within the exposure apparatus 400 senses a pressure within the exposure apparatus 400, and the pressure within the exposure apparatus 400 is controlled by a vacuum pressure controller 406 coupled to the exposure apparatus 400. In some embodiments, the reflective mask 205c is consistent with the reticle 80 described with respect to Figure 5A In some embodiments, the vacuum pressure controller 406 is included in the rapid exchange device (RED) controller 240 of Figure 2 In some embodiments, the vacuum pressure controller 406 is included in the rapid exchange device (RED) controller 240 of

[0110] In some embodiments, the target semiconductor substrate 210 is a dummy wafer and the exposure device 400 is identical to the first exposure device 212. As described with respect to Figure 2 the reticle taken from the reticle library 200 is loaded into the exposure device 400 as a reflective mask 205c. In some embodiments, Figure 4 the semiconductor substrate 210 is a dummy wafer and the reflective mask 205c is irradiated with radiation from the radiation source 100 for a predetermined amount of time to clean the surface of the reticle of particles and / or hydrocarbon contaminants.

[0111] Figures 5A-5B is a cross-sectional view of a reflective reticle structure 80 and projection of the reflective reticle structure 80 in a semiconductor device 34 in an exposure device. Figure 5A A cross-sectional view 500 of a reflective reticle structure 80 (e.g., a reflective mask) is shown. As described above, the terms "mask," "photomask," and "reticle" are used interchangeably. The reflective reticle structure 80 is identical to Figure 4 the reflective mask 205c and the reflective reticle structure 80 is used in Figure 4 the exposure structure 400. As shown Figure 5A , the reflective reticle structure 80 includes a substrate 30 having a suitable structure, such as a low thermal expansion material or fused silica. In various examples, the material includes titanium dioxide (TiO2) doped with silicon dioxide (SiO2) or other suitable material having low thermal expansion properties. The mask includes a plurality of reflective layers (ML) 35 deposited on the substrate 30. The plurality of reflective layers (ML) 35 includes a plurality of thin film pairs (thin film 37 and thin film 39), such as molybdenum-silicon (Mo / Si) thin film pairs (e.g., a layer of molybdenum above or below a layer of silicon in each thin film pair). Alternatively, the plurality of reflective layers (ML) 35 can include molybdenum-beryllium (Mo / Be) thin film pairs, or other suitable material configured to highly reflect extreme ultraviolet (EUV) light. The mask can also include a capping layer 40, such as ruthenium (Ru), disposed on the reflective layers (ML) for protection. The mask further includes an absorbing layer 45, such as a tantalum boron nitride (TaBN) layer, deposited on the reflective layers (ML). The absorbing layer 45 is patterned to define a layout pattern 55 for a layer of an integrated circuit. Alternatively, other reflective layers can be deposited on the reflective layers (ML) and patterned to define a layer of an integrated circuit, thereby forming an extreme ultraviolet (EUV) phase shift mask.

[0112] Figure 5B is shown exposing a photoresist layer disposed on a semiconductor device to radiation.Figure 5B is a simplified diagram consistent with Figure 4 for projecting a reflective mask onto a substrate. Figure 5A Also shown is a semiconductor device 34 including a photoresist layer 15 disposed on a semiconductor substrate 10, and the semiconductor substrate 10 is consistent with Figure 4 the semiconductor substrate 210 of Figure 5B Also shown is a radiation beam 50 originating from an extreme ultraviolet (EUV) light source (e.g. Figure 4 the extreme ultraviolet (EUV) light source of ). The radiation beam 50 is directed to a photomask 80, such as a reflective light mask, where a reflected beam 50' reflected from the reflective light mask 80 is incident on the photoresist layer 15 of the semiconductor device 34. The angle of incidence of the reflected beam 50' is an angle A defined with respect to a line 302 normal to the top surface of the semiconductor substrate 10. In some embodiments, the semiconductor substrate 10 is consistent with the semiconductor substrate 210 of Figure 4 the semiconductor substrate 210 of is mounted on a stage 560, which is coupled to and controlled by a stage controller 565 for moving the semiconductor device 34 and for exposing different locations of the semiconductor device 34. In some embodiments, as described above, Figure 5B the exposure configuration 550 is part of Figure 4 the exposure device 400 of

[0113] Figure 6 is an inspection system 600 for a photoresist pattern disposed on the semiconductor substrate 10. Figure 6 is shown on a stage 660, which is coupled to and controlled by a stage controller 665. As described above with respect to Figure 2 after cleaning the photomask at the first exposure device 212, the photomask is loaded into the exposure device 400 as a reflective photomask 205c. In some embodiments, the semiconductor substrate 210 of Figure 4 is the semiconductor device 34 of Figure 5B and the reflective mask 205c is illuminated with a radiation beam of the radiation source 100 to project a layout pattern of the reflective mask 205c onto the photoresist layer 15 of the semiconductor device 34 to produce a photoresist pattern in the photoresist layer 15. In some embodiments, prior to the exposure, a post-apply bake (PAB) operation 104 is performed to bake the substrate 10 including the photoresist layer 15 to drive out solvents in the photoresist material and to cure the photoresist layer 15. In some embodiments, after the exposure, a post-exposure bake (PEB) operation 110 is performed on the photoresist layer 15. In some embodiments, after the post-exposure bake (PEB) operation 110, a development operation 112 is applied to the photoresist layer 15 to produce the photoresist pattern in the photoresist layer 15.

[0114] Figure 6A scanning imaging device 635 is also shown that generates a focused beam 619 for scanning the top surface of the photoresist layer 15 and generates an image of the photoresist pattern at the top surface of the photoresist layer 15. Further, Figure 6 A scanning imaging device 635 that generates a uniform beam 617 for imaging the top surface of the photoresist layer 15 and generates an image of the photoresist pattern on the top surface of the photoresist layer 15 is shown with a lens 634. Further, the scanning imaging device 635 is coupled to an analyzer module 630 that includes an image processing unit 633 to receive and process the generated image of the top surface of the photoresist layer 15. In some embodiments, the generated image of the photoresist pattern on the top surface of the photoresist layer 15 is inspected. In some embodiments, the image processing unit 633 of the analyzer module 630 performs one or more image processing and / or image recognition algorithms on the generated image of the top surface of the photoresist layer 15 and determines a critical dimension (CD) measurement of the photoresist pattern generated in the photoresist layer 15. In some embodiments, the focused beam 619 and the uniform beam 617 are optical beams. In some embodiments, the focused beam 619 is an electron beam. In some embodiments, as previously described, the semiconductor device 34 is placed on a stage 660 and a stage controller 665 of the stage 660 moves the semiconductor device 34 relative to the scanning imaging device 635. In some embodiments, the stage controller 665 coordinates the movement of the scanning imaging device 635 and the semiconductor device 34 placed on the stage 660 and the stage controller 665 enables the scanning imaging device 635 to capture one or more images of the developed photoresist pattern of the photoresist layer 15 disposed on the semiconductor device 34 at different locations of the semiconductor device 34.

[0115] In some embodiments, the analyzer module 630 or the image processing unit 633 of the analyzer module 630 also determines the critical dimension uniformity (CD uniformity, CDU) of the developed photoresist pattern of the photoresist layer 15. If the critical dimension uniformity (CDU) meets a predetermined criterion, e.g., if the critical dimension uniformity (CDU) is better than one percent, then the analyzer module 630 determines that the predetermined amount of time for cleaning particles and / or hydrocarbon contaminants from the surface of the photomask is sufficient, e.g., is acceptable. However, if the critical dimension uniformity (CDU) does not meet the predetermined criterion, then the analyzer module 630 determines that the predetermined amount of time for cleaning particles and / or hydrocarbon contaminants from the surface of the photomask is insufficient, e.g., is unacceptable, and the predetermined amount of time should be increased. In some embodiments, the analyzer module gradually increases the predetermined amount of time, e.g., the predetermined amount of time is increased in steps of between about 2% and about 10%, for example. After each step of increasing the predetermined amount of time, the critical dimension uniformity (CDU) is measured and if the critical dimension uniformity (CDU) meets the predetermined criterion, then the increasing of the predetermined amount of time is not continued and the predetermined amount of time is determined to be the amount of time for which the critical dimension uniformity (CDU) meets the predetermined criterion. In some embodiments, the predetermined amount of time depends on the details of the layout pattern of the mask and whether there are particular shapes or features in the layout pattern of the mask.

[0116] In some embodiments, the analyzer module 630 determines that the predetermined amount of time for cleaning particles and / or hydrocarbon contaminants from the surface of the photomask is acceptable, however, the predetermined amount of time can be more than the time for which the predetermined criterion is met. In some embodiments, the analyzer module 630 gradually decreases the predetermined amount of time, e.g., the predetermined amount of time is decreased in steps of between about 2% and about 10%, for example. After each step of decreasing the predetermined amount of time, the critical dimension uniformity (CDU) is measured and when the critical dimension uniformity (CDU) at that step does not meet the predetermined criterion, the decreasing of the predetermined amount of time is not continued and the predetermined amount of time is determined to be the amount of time immediately prior to the decrease that resulted in the critical dimension uniformity (CDU) not meeting the predetermined criterion. In some embodiments, the determined predetermined amount of time is increased by a predetermined percentage, e.g., between about 0.5% and about 1.5%, to increase reliability.

[0117] Figures 7A-7F An exposure device for measuring reflected projection light from a reflective photomask according to some embodiments of the present disclosure. Figures 7A-7F Similar to Figure 5 showing the reflective photomask 80 being illuminated with a beam of radiation 50. The light source 705 is in accordance with the radiation source 100 of Figure 4 and the reflective photomask 80 is in accordance with the reflective photomask 80 of Figure 4The reflective mask 205c is consistent with the exposure apparatus 400. However, unlike the exposure apparatus 400, the reflective beam 50' is not directed to the substrate, but consistent with the exposure apparatus 212, the reflective beam 50' is directed to the photodetector system 710 to detect the projected image from the reflective mask 80, such as the projected layout pattern. The detected image is transmitted to the analyzer module 630 for analysis. Figure 5B Consistent, the incident angle of the reflected beam 50' is angle A, which is defined relative to line 302 perpendicular to surface 706.

[0118] like Figure 7A , Figure 7B , Figure 7C As shown, particle 702 is located on surface 706 of the photomask (photomask 80 into which the radiation beam 50 enters). Particle 702 may degrade the projected image during lithography and may affect critical dimension (CD) uniformity. In some embodiments, light source 705 is an extreme ultraviolet (EUV) light source and light source 705 irradiates particle 702 with extreme ultraviolet (EUV) radiation to decompose particle 702. As... Figures 7A-7B Progress and Figures 7B-7C As the progress is shown, particle 702 decomposes and becomes smaller. In some embodiments, the photomask 80 is irradiated with radiation beam 50 and the image detector system continuously captures the projected image of the photomask 80 for a predetermined amount of time, such that particle 702 does not affect critical size uniformity (CDU) and the critical size uniformity (CDU) satisfies the threshold critical size uniformity (CDU).

[0119] like Figures 7D-7E As shown, a contaminant layer 704 containing hydrocarbon contaminants is deposited on the surface 706 of the photomask (photomask 80 into which the radiation beam 50 enters). The contaminant layer 704 may degrade the projected image during lithography and may affect critical size (CD) uniformity. In some embodiments, the contaminant layer 704 is irradiated with extreme ultraviolet (EUV) radiation to decompose the contaminant layer 704. As... Figures 7D-7E As progress is made, the contaminant layer 704 is decomposed and thinned. In some embodiments, the photomask 80 is irradiated with a radiation beam 50 and the image detector system continuously captures the projected image of the photomask 80 for a predetermined amount of time, such that the contaminant layer 704 does not affect the critical size uniformity (CDU), and the critical size uniformity (CDU) is maintained within a threshold of approximately 1% to 2% in the 3-nanometer process of the 3-nanometer semiconductor node.

[0120] In some embodiments, the projected image of the photomask 80 captured by the image detector system 710 is further continuously scanned by the image detector system 710. The scan provides detection points for the entire projected image of the photomask 80 at different time instances. In some embodiments, the scanned projected image of the photomask 80 provides both the temporal variation of the entire projected image and the spatial variation of the projected image at a specific time instance. Figure 7F The image shows the temporal variation of the intensity of a specific point in the captured projected image of the photomask 80 at coordinates 732 and time coordinates 734. (Example) Figure 7F As shown, the reflection intensity at a specific point increases over time until the intensity curve saturates at level S1 and no longer increases further at time T1. Curve 738 represents the presence of particles or hydrocarbon contamination at a specific point, and the irradiation of the point by the radiation beam 50 causes the particles to break down and increase the reflected light intensity. In some embodiments, time T1 is a predetermined amount of time required to clean the surface 706 of the photomask 80, and further irradiation of the photomask 80 will not improve the reflected light intensity. In some embodiments, cleaning stops and time T1 is reached when curve 738 saturates within a predetermined time and the increase of curve 738 within the predetermined time is less than a threshold, for example, when the increase of curve 738 within 5 seconds is less than one percent. In some embodiments, time T1 is between about 50 seconds and about 100 seconds. In some embodiments, curve 738 is constructed for multiple points on the surface of the photomask 80, time T1 is measured for multiple points, and finally T1 is determined as the maximum value of the measured time T1s.

[0121] Figure 8 A control system 800 according to some embodiments of the present disclosure is used for cleaning a photomask and for projecting a layout pattern of the cleaned photomask onto a semiconductor substrate. The control system 800 includes an analyzer module 830 and a main controller 840 coupled to each other. In some embodiments, the control system 800 includes... Figure 6 Platform controller 665 Figure 7A Image detector system 710 Figure 2 Fast Exchange (RED) controller 240, Figure 6 The scanning imaging device 635, and Figure 4 The vacuum pressure controller 406. In some embodiments, the main controller 840 controls and is coupled to the stage controller 665, the image detector system 710, the fast exchange device (RED) controller 240, the scanning imaging device 635, and the vacuum pressure controller 406. In some embodiments, the main controller 840 is directly coupled to the scanning imaging device 635, or the main controller 840 is coupled to the scanning imaging device 635 through the analyzer module 830.

[0122] In some embodiments, the analyzer module 830 includes Figure 6Analyzer module 630, or analyzer module 830 and Figure 6 The analyzer module 630 is consistent with this. In some embodiments, the main controller 840 commands the scanning imaging device 635 to capture images of photoresist patterns on a semiconductor substrate and determines (e.g., measures) the critical size uniformity (CDU) of the photoresist patterns disposed on the semiconductor substrate, via the analyzer module 830. As described above, the analyzer module 830 determines whether the surface of the photomask is cleaned based on the measured critical size uniformity (CDU). In some embodiments, the main controller 840 commands the stage controller 665 to move the stage 660 to capture one or more images of photoresist patterns disposed at different locations on the semiconductor substrate. In some embodiments, the main controller 840 commands the vacuum pressure controller 406 to maintain a vacuum environment inside the first exposure device 212 and the second exposure device 214 and to maintain a vacuum environment inside the photomask library 202. In some embodiments, the main controller 840 commands the fast exchange device (RED) controller 240 to clean the surface of the photomask in the first exposure device 212, load the cleaned photomask into the second exposure device 214, and project the layout pattern of the photomask onto the photoresist layer of the substrate. In some embodiments, the main controller 840 commands the image detector system 710 to capture reflected images from the photomask during photomask cleaning and transmit the captured reflected images to the analyzer module 830 for analysis.

[0123] In some embodiments, the analyzer module 830 includes a data exploration module 818, a machine learning module 816, and a neural network module 814. As previously described, in some embodiments, the analyzer module 830 includes an image processing unit 633, which includes the data exploration module 818, the machine learning module 816, and the neural network module 814. In some embodiments, the data exploration module 818, the machine learning module 816, or the neural network module 814 continuously scans the captured reflected images, determines data corresponding to reflected light from different locations on the photomask, analyzes the data, and instantly determines changes in the data to determine when particulate and / or hydrocarbon contaminants are removed from the surface of the photomask.

[0124] Figure 9 This is a flowchart of an example process 900 for cleaning a photomask and for projecting a layout pattern of the cleaned photomask onto a semiconductor substrate, according to some embodiments of this disclosure. Process 900 or a portion thereof may be provided by Figure 2 The system executes. In some embodiments, process 900 or a portion thereof is referred to as follows Figure 10A and Figure 10B The described computer system 1000 performs and / or controls. In some embodiments, process 900 or a portion of process 900 is performed by the aforementioned... Figure 8The system 800 performs. The process 900 includes operation S910, which retrieves a reticle from a reticle library and transfers the reticle to a first exposure device. As shown in Figure 2 , a robotic device 206 retrieves a reticle from a reticle library 202. After retrieving the reticle, the robotic device transfers the reticle to a first exposure device 212.

[0125] At operation S920, the surface of the reticle is cleaned by irradiating the surface of the reticle with extreme ultraviolet (EUV) radiation of an EUV radiation source for a predetermined amount of time in the first exposure device. As shown in Figures 7A-7C , a particle 702 on the surface of the reticle 80 is cleaned in the first exposure device 212. As shown in Figure 7D , a hydrocarbon contaminant 704 on the surface of the reticle 80 is cleaned. Figure 7E

[0126] At operation S930, after cleaning, the reticle is transferred from the first exposure device to a second exposure device for a lithography operation. As shown in Figure 2 , after cleaning the reticle, the reticle is transferred from the first exposure device 212 to a second exposure device 214. The reticle is transferred by a robotic device 206. A lithography operation is performed in the second exposure device using the layout pattern of the reticle.

[0127] At operation S940, the layout pattern of the reticle is projected onto a photoresist layer of a wafer in the second exposure device. As shown in Figure 4 , or Figure 5B , the layout pattern of each reflective mask 205c or 80 is projected onto a photoresist layer of a respective semiconductor substrate 210 or 10.

[0128] Figures 10A-10B An apparatus for cleaning a reticle and for projecting a layout pattern of the cleaned reticle on a semiconductor substrate according to some embodiments of the present disclosure. In some embodiments, the computer system 1000 is used to perform the functions of the modules of Figure 8 , including the main controller 840, the analyzer module 830 or 630, the stage controller 665, the rapid exchange device (RED) controller 240, the vacuum pressure controller 406, and the image processing unit 633 of the analyzer module 630. In some embodiments, the computer system 1000 is used to perform the process 900. Figure 9

[0129] Figure 10A A schematic diagram of a computer system for performing the functions of an apparatus for cleaning a reticle and for projecting a layout pattern of the cleaned reticle. All or part of the processes, methods, and / or operations of the above-described embodiments can be implemented using computer hardware and computer programs executing thereon. In Figure 10A ​​In the embodiment, the computer system 1000 is equipped with a computer 1001 including an optical disc read-only memory (e.g., CD-ROM or DVD-ROM) drive 1005 and a magnetic disc drive 1006, a keyboard 1002, a mouse 1003, and a screen display 1004.

[0130] Figure 10B A schematic diagram showing the internal configuration of the computer system 1000 is shown in FIG. 1. In the embodiment, the computer 1001 has one or more processors, such as a micro processing unit (MPU) 1011, a read only memory (ROM) 1012, a random access memory (RAM) 1013, a hard disk 1014, and a bus 1015, in addition to the optical disc drive 1005 and the magnetic disc drive 1006. Figure 10B The read only memory (ROM) 1012 stores programs such as a boot up program. The random access memory (RAM) 1013 is connected to the micro processing unit (MPU) 1011, and temporarily stores commands of an application program and provides a temporary area. The hard disk 1014 stores application programs, system programs, and data. The bus 1015 connects the micro processing unit (MPU) 1011, the read only memory (ROM) 1012, and the like. It should be noted that the computer 1001 can include a network card (not shown) for providing connection to a local area network (LAN).

[0131] The program for causing the computer system 1000 to perform the functions of cleaning a photomask and projecting a layout pattern of the cleaned photomask in the above-described embodiments can be stored in the optical disc 1021 or the magnetic disc 1022 and transferred to the hard disk 1014, the optical disc 1021 or the magnetic disc 1022 being inserted into the optical disc drive 1005 or the magnetic disc drive 1006. Alternatively, the program can be transferred to the computer 1001 through a network (not shown) and stored in the hard disk 1014. Upon execution, the program is loaded into the random access memory (RAM) 1013. The program can be loaded from the optical disc 1021 or the magnetic disc 1022, or can be loaded directly from the network. The program does not necessarily have to include, for example, an operating system (OS) or a third party program to cause the computer 901 to perform the functions of the control system for cleaning a photomask and projecting a layout pattern of the cleaned photomask in the above-described embodiments. The program can only include a command portion to call appropriate functions (modules) in a controlled mode and obtain a desired result.

[0132] One aspect of the present disclosure relates to a method, comprising: retrieving a reticle from a reticle library; transferring the reticle to a first exposure device; cleaning a surface of the reticle in the first exposure device by irradiating the surface of the reticle with a first extreme ultraviolet radiation for a predetermined irradiation time; and after cleaning the surface of the reticle, transferring the reticle to a second exposure device for a lithography operation. In some embodiments, the method further comprises: maintaining the first exposure device, the second exposure device, and the reticle library in a vacuum environment. In some embodiments, the reticle is retrieved from the reticle library and transferred to the first exposure device by a robot of a rapid exchange device; the method further comprises: transferring the reticle from the first exposure device to the second exposure device by the robot of the rapid exchange device. In some embodiments, the method further comprises: projecting a layout pattern of the reticle onto a photoresist layer of a wafer by a second extreme ultraviolet radiation; and developing the photoresist layer to produce a photoresist pattern on the wafer. In some embodiments, the first extreme ultraviolet radiation is generated by a first extreme ultraviolet light source, and the second extreme ultraviolet radiation is generated by a second extreme ultraviolet light source different from the first extreme ultraviolet light source. In some embodiments, the method further comprises: imaging a surface of the wafer to produce an image of the photoresist pattern on the wafer; analyzing the image of the photoresist pattern to determine a critical dimension uniformity of the photoresist pattern; and if the critical dimension uniformity does not satisfy a threshold critical dimension uniformity, increasing the predetermined irradiation time. In some embodiments, the method further comprises: repeating the cleaning the surface of the reticle, the projecting the layout pattern of the reticle onto the photoresist layer of the wafer, the developing the photoresist layer, the imaging the surface of the wafer, the analyzing the image of the photoresist pattern, and the increasing the irradiation time until the critical dimension uniformity satisfies the threshold critical dimension uniformity; and adjusting the predetermined irradiation time to an irradiation time corresponding to the threshold critical dimension uniformity.

[0133] Another aspect of the present disclosure relates to a method, comprising: cleaning a surface of a reticle in a first exposure device with extreme ultraviolet radiation of a first extreme ultraviolet light source at an irradiation time; after cleaning the surface of the reticle, transferring the reticle from the first exposure device to a second exposure device for a lithography operation; and projecting a layout pattern of the reticle onto a photoresist layer of a wafer in the second exposure device using extreme ultraviolet radiation of a second extreme ultraviolet light source. In some embodiments, the method further comprises: after projecting the layout pattern of the reticle onto the photoresist layer of the wafer, developing the photoresist layer to produce a photoresist pattern on the wafer. In some embodiments, the reticle is a reflective reticle, and the method further comprises: cleaning the surface of the reticle at the first exposure device by irradiating an entire surface of the reticle with an extreme ultraviolet beam; focusing a reflected light from the entire surface of the reticle onto an image detector to produce a detected reflected image; monitoring the detected reflected image during the irradiation time; and stopping cleaning the surface of the reticle when an increase of each point of the detected reflected image in a certain amount of time is below a threshold. In some embodiments, the method further comprises: continuously scanning the entire surface of the reticle by continuously sampling the detected reflected image of the image detector to produce a detected scan signal at the first exposure device during cleaning the surface of the reticle, wherein each time of the detected scan signal corresponds to a location on the surface of the reticle; monitoring the detected scan signal of each location during the irradiation time; and stopping cleaning the surface of the reticle when an increase of the detected scan signal of each location in a certain amount of time is below a threshold. In some embodiments, the method further comprises: analyzing the detected scan signal by one of a pattern recognition algorithm, a data mining algorithm, and a neural network algorithm to determine a plurality of corresponding locations of the surface of the reticle that need to be cleaned. In some embodiments, the first extreme ultraviolet light source of the first exposure device produces extreme ultraviolet radiation of 13.5 nanometers. In some embodiments, the method further comprises: maintaining the first exposure device and the second exposure device in a vacuum environment.

[0134] Yet another aspect of the present disclosure relates to a system, comprising: a main controller, an analyzer module coupled to the main controller, a rapid exchange device having an extendable robotic arm, a first exposure device, and a second exposure device. The first exposure device comprises a first reticle stage and a first extreme ultraviolet light source. The first reticle stage is configured to hold a reticle. The second exposure device comprises a second reticle stage, a second extreme ultraviolet light source, a stage, and an optical system. The stage is configured to hold a wafer. The main controller is configured to command the first extreme ultraviolet light source to turn on, the first extreme ultraviolet light source turning on to irradiate extreme ultraviolet radiation from the first extreme ultraviolet light source, and the first extreme ultraviolet light source turning on to clean a surface of the reticle in the first reticle stage of the first exposure device by irradiating the surface of the reticle with the extreme ultraviolet radiation of the first extreme ultraviolet light source for a predetermined irradiation time. After cleaning the surface of the reticle, the main controller is configured to command the rapid exchange device to transfer the reticle from the first exposure device to the second reticle stage of the second exposure device for a lithography operation by the extendable robotic arm. After transferring the reticle from the first exposure device to the second reticle stage of the second exposure device, the main controller is configured to command the second extreme ultraviolet light source to turn on, the second extreme ultraviolet light source turning on to irradiate extreme ultraviolet radiation from the second extreme ultraviolet light source, and the second extreme ultraviolet light source turning on to project a layout of the reticle onto a photoresist layer of the wafer through the optical system. In some embodiments, the system further comprises a developing system configured to develop the photoresist layer after projecting the layout of the reticle onto the photoresist layer of the wafer and to produce a photoresist pattern on the wafer. In some embodiments, the above-mentioned second exposure device further comprises an imaging device mounted on the stage, wherein in response to a command from the main controller, the imaging device is configured to capture an image of the developed photoresist pattern on the surface of the wafer and to transmit the captured image to the analyzer module; wherein the analyzer module is configured to determine a critical dimension uniformity of the photoresist pattern on the wafer. In some embodiments, the system further comprises a reticle library configured to hold a plurality of reticles, and a pressure controller coupled to the main controller, the pressure controller being configured to maintain a pressure of the first exposure device, the second exposure device, and the reticle library in a vacuum environment. In some embodiments, the system further comprises a reticle library, wherein before irradiating the surface of the reticle with the extreme ultraviolet radiation, the main controller is configured to transmit a command to the rapid exchange device to retrieve a reticle from the reticle library and to transfer the reticle to the first exposure device. In some embodiments, the first extreme ultraviolet light source and the second extreme ultraviolet light source have a wavelength of 13.5 nanometers.

[0135] As described in the above embodiments, particles deposited on a surface of a reticle and a hydrocarbon layer deposited on the surface of the reticle are decomposed by extreme ultraviolet (EUV) radiation to clean the surface of the reticle. The particles and the hydrocarbon layer on the surface of the reticle are cleaned by using the extreme ultraviolet (EUV) radiation without a solvent.

[0136] The foregoing outlines features of several embodiments so that those skilled in the art can better understand the aspects of the disclosure. Those skilled in the art should appreciate that they can readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and / or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure, and that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the disclosure.

Claims

1. A method of cleaning a surface of a photomask, characterized by, comprising: retrieving a reticle from a reticle library; transferring the reticle to a first exposure device; cleaning a surface of the reticle in the first exposure device by irradiating the surface of the reticle with a first extreme ultraviolet radiation for a predetermined irradiation time; after cleaning the surface of the reticle, transferring the reticle to a second exposure device for lithography operation; projecting a layout pattern of the reticle onto a photoresist layer of a wafer by a second extreme ultraviolet radiation; developing the photoresist layer to produce a photoresist pattern on the wafer; imaging a surface of the wafer to produce an image of the photoresist pattern on the wafer; analyzing the image of the photoresist pattern to determine a critical dimension uniformity of the photoresist pattern; and if the critical dimension uniformity does not satisfy a threshold critical dimension uniformity, increasing the predetermined irradiation time.

2. The method of claim 1, wherein, further comprising: maintaining the first exposure device, the second exposure device, and the reticle library under a vacuum environment.

3. The method of claim 1, wherein, wherein the reticle is retrieved from the reticle library and transferred to the first exposure device by a robot of a fast exchange device; and the method further comprises transferring the reticle from the first exposure device to the second exposure device by the robot of the fast exchange device.

4. The method of claim 1, wherein, wherein the first extreme ultraviolet radiation is generated by a first extreme ultraviolet light source, and wherein the second extreme ultraviolet radiation is generated by a second extreme ultraviolet light source different from the first extreme ultraviolet light source.

5. The method of claim 1, wherein, further comprising: repeating the cleaning the surface of the reticle, the projecting the layout pattern of the reticle onto the photoresist layer of the wafer, the developing the photoresist layer, the imaging the surface of the wafer, the analyzing the image of the photoresist pattern, and the increasing the irradiation time until the critical dimension uniformity satisfies the threshold critical dimension uniformity; and adjusting the predetermined irradiation time to the irradiation time corresponding to the threshold critical dimension uniformity.

6. A method of cleaning a surface of a photomask, characterized by, comprising: cleaning a surface of a reticle in a first exposure device by irradiating the surface of the reticle with an extreme ultraviolet radiation of a first extreme ultraviolet light source for an irradiation time; cleaning the surface of the reticle in the first exposure device by irradiating an entire surface of the reticle with an extreme ultraviolet light beam; focusing a reflected light from the entire surface of the reticle onto an image detector to produce a detected reflected image; monitoring the detected reflected image during the irradiation time; stopping cleaning the surface of the reticle when an increase of each point of the detected reflected image is below a threshold value in a certain amount of time; after cleaning the surface of the reticle, transferring the reticle from the first exposure device to a second exposure device for lithography operation; and projecting a layout pattern of the reticle onto a photoresist layer of a wafer in the second exposure device using an extreme ultraviolet radiation of a second extreme ultraviolet light source, wherein the reticle is a reflective reticle.

7. The method of claim 6, wherein, further comprising: developing the photoresist layer to produce a photoresist pattern on the wafer after projecting the layout pattern of the reticle onto the photoresist layer of the wafer.

8. The method of claim 6, wherein, the method further comprises: a whole surface of the photomask is continuously scanned by continuously sampling a detected reflected image of an image detector to generate a detected scan signal at the first exposure device during cleaning of the surface of the photomask, wherein each of the detected scan signals corresponds to a location on the surface of the photomask; monitoring the detected scan signal of each of the locations during the irradiation time; and stopping cleaning of the surface of the photomask when an increase of the detected scan signal of each of the locations is below a threshold value in a certain amount of time.

9. The method of claim 8, wherein, Further comprising: analyzing the detected scan signal by one of a pattern recognition algorithm, a data mining algorithm, and a neural network algorithm to determine corresponding locations of the surface of the photomask that need to be cleaned.

10. The method of claim 6, wherein, The first EUV source of the first exposure device generates the EUV radiation at 13.5 nanometers.

11. The method of claim 6, wherein, Further comprising: maintaining the first exposure device and the second exposure device in a vacuum environment.

12. A system for cleaning a surface of a photomask, the system comprising: Comprising: a main controller; an analyzer module coupled to the main controller; a rapid exchange device having an extendable robot arm; a first exposure device comprising: a first photomask stage to hold a photomask; and a first EUV source; a second exposure device comprising: a second photomask stage; a second EUV source; a stage to hold a wafer; an imaging device mounted on the stage, wherein in response to a command from the main controller, the imaging device is to capture an image of a developed photoresist pattern on a surface of the wafer and to transmit the captured image to the analyzer module, wherein the analyzer module is to determine a critical dimension uniformity of the photoresist pattern on the wafer; and an optical system; and a developing system to develop a photoresist layer on the wafer after projecting a layout of the photomask onto the photoresist layer and to generate the photoresist pattern on the wafer; wherein the main controller is to command the first EUV source to turn on to irradiate an EUV radiation by the first EUV source and to turn on to irradiate a surface of the photomask in the first photomask stage with the EUV radiation of the first EUV source for a predetermined irradiation time to clean the surface of the photomask; wherein after cleaning the surface of the photomask, the main controller is to command the rapid exchange device to transfer the photomask from the first exposure device to the second photomask stage of the second exposure device for lithography operation by the extendable robot arm; wherein after transferring the photomask from the first exposure device to the second photomask stage of the second exposure device, the main controller is to command the second EUV source to turn on to irradiate an EUV radiation by the second EUV source and to turn on to project the layout of the photomask onto the photoresist layer of the wafer through the optical system.

13. The system of claim 12, wherein, Further comprising: a photomask library to hold a plurality of photomasks; and a pressure controller coupled to the main controller, wherein the pressure controller is to maintain a pressure of the first exposure device, the second exposure device, and the reticle library in a vacuum environment.

14. The system of claim 12, wherein, Also included are: a reticle library, wherein the main controller is to transmit a command to the fast exchange device to retrieve the reticle from the reticle library and to transfer the reticle to the first exposure device prior to the surface of the reticle being illuminated with the extreme ultraviolet radiation.

15. The system of claim 12, wherein, The first extreme ultraviolet light source and the second extreme ultraviolet light source have a wavelength of 13.5 nanometers.

Images