Lithography system

Abstract

The utility model provides a photoetching system. The photoetching system comprises a top part; the mask table is arranged on the top part; a bottom portion; the film protecting table is positioned at the bottom part; and the second optical detector is mounted on the mask table, and the second optical detector faces the film protecting table. The lithographic system may detect particles via an optical detector, which reduces rework and increases utilization.

Description

Technical Field

[0001] The utility model relates to a system, in particular to a photolithography system. Background Art

[0002] The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced several generations of ICs, each with smaller and more complex circuits than the previous generation. During the development of ICs, functional density (i.e., the number of interconnected devices per chip area) has generally increased, while geometry size (i.e., the smallest component (or line) that can be created using a manufacturing process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and reducing associated costs. This scaling down also increases the complexity of processing and manufacturing ICs. Utility Model Content

[0003] An embodiment of the utility model provides a lithography system comprising: a top part; a mask stage arranged on the top part; a bottom part; a pellicle stage located on the bottom part; and a second optical detector installed on the mask stage, the second optical detector facing the pellicle stage.

[0004] Based on the above, the lithography system can detect particles via optical detectors, which reduces rework and improves utilization.

[0005] In order to make the above features and advantages of the embodiments of the present invention more obvious and easy to understand, embodiments are specifically cited below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1A and Figure 1B A diagram of a portion of a lithography scanner is depicted according to an embodiment of the present disclosure.

[0007] FIG. 2A to FIG. 2C Various embodiments of a mask assembly for a lithography scanner are depicted in accordance with various aspects of the present disclosure.

[0008] Figures 3A to 3G Schematic diagram of using a protective film according to various embodiments.

[0009] Figure 4 2 is a diagram illustrating a process of attaching a pellicle to a mask assembly according to various embodiments.

[0010] FIG. 5A to FIG. 5D A diagram illustrating a process of attaching a pellicle to a mask assembly according to various aspects of the present disclosure.

[0011] 6A to 6F In accordance with various aspects of the present disclosure, a diagram of a process for in-situ scanning of pellicles and masks is depicted.

[0012] Figure 7 is a flow chart depicting a process of performing a semiconductor process using a mask assembly with a pellicle attached thereto according to various embodiments.

[0013] Figure 8 is a flow chart of scanning a mask and a pellicle prior to installation according to various embodiments.

[0014] Description of Reference Numerals

[0015] 10: Lithography exposure system, EUV system, lithography system;

[0016] 16: mask stage;

[0017] 18: mask;

[0018] 22: semiconductor wafer;

[0019] 24: Substrate table;

[0020] 26: mask layer;

[0021] 30: droplet generator;

[0022] 31: liquid storage tank;

[0023] 32: nozzle assembly;

[0024] 35: drip receiver;

[0025] 41: Gas pipeline;

[0026] 50: laser generator;

[0027] 51: Laser pulse;

[0028] 52: lighting point;

[0029] 55: windows, lenses;

[0030] 60: Laser generated plasma collector, segmented collector, collector;

[0031] 61: optical axis;

[0032] 65: Container wall;

[0033] 66: first pump;

[0034] 68: Second pump;

[0035] 70: Monitoring device;

[0036] 71: measuring tools;

[0037] 73: Analyzer;

[0038] 80: target fuel, target substance;

[0039] 82: drops;

[0040] 84: EUV radiation, EUV light;

[0041] 88: Plasma;

[0042] 90: controller;

[0043] 180: projection optical module, projection optical box;

[0044] 100: reflector;

[0045] 120: light source;

[0046] 140: Illuminator;

[0047] 200: mask assembly;

[0048] 216: mask stage;

[0049] 218: mask;

[0050] 220: semiconductor wafer;

[0051] 225: Region;

[0052] 230: mask pattern, metal layer;

[0053] 250: particles;

[0054] 360:frame;

[0055] 362: Holes;

[0056] 370: protective film;

[0057] D1: height;

[0058] D2, D3: distance;

[0059] 370S, 370L, 350I, 350T, 350P: particles;

[0060] D4, D5: diameter;

[0061] 410, 411, 412, 420, 430, 440, 450, 511A, 511B, 511C, 511D, 511E, 511F, 511G, 700, 710, 720, 722, 724, 730, 740, 750, 760, 762, 764, 770, 772, 774, 780, 810, 820, 830, 840, 850: operation;

[0062] 500: Install the system;

[0063] 513: Plasma etcher;

[0064] 514: SMIF pod;

[0065] 518: substrate;

[0066] 520: Robots, robot arms;

[0067] 522: mask stage;

[0068] 530: Installer, installation device;

[0069] 532: film table;

[0070] 536: bottom part;

[0071] 538: top part;

[0072] 540: Film box;

[0073] 542: protective film assembly;

[0074] 600, 600A: a first optical detector, a SD-OCT imaging device;

[0075] 602: a second optical detector;

[0076] 610: optical module;

[0077] 612: Shell;

[0078] 620: light source;

[0079] 630: Spectrometer, interferometer;

[0080] 640: Reference mirror;

[0081] 650: detection sensor;

[0082] 652: Image;

[0083] 654, 656, 658: Interference wave pattern;

[0084] 670: Mirror;

[0085] 680: Lens;

[0086] 690: objective lens;

[0087] 701, 801: process, technology, method. DETAILED DESCRIPTION

[0088] The following disclosure provides many different embodiments or examples to implement the different features of the present invention. The following disclosure describes specific examples of each component and its arrangement to simplify the description. Of course, these specific examples are not intended to be limiting. For example, if an embodiment of the present invention describes that a first characteristic component is formed on or above a second characteristic component, it means that it may include an embodiment in which the first characteristic component and the second characteristic component are in direct contact, and may also include an embodiment in which an additional characteristic component is formed between the first characteristic component and the second characteristic component, so that the first characteristic component and the second characteristic component may not be in direct contact. In addition, the embodiments of the present invention may reuse numbers and / or text in each example. This repetition is for the purpose of brevity and clarity, and does not itself represent the relationship between the various embodiments and / or configurations discussed.

[0089] Additionally, for ease of description, spatially relative terms, such as "beneath," "below," "lower," "above," "upper," etc., may be used herein to describe the relationship of one component or feature to another component or feature, as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0090] Terms such as "about", "roughly", "substantially" and the like may be used herein for convenience of description. A person having ordinary skill in the art will be able to understand and deduce the meaning of these terms.

[0091] The present disclosure relates generally to lithography equipment used to manufacture semiconductor devices, and more particularly to methods of inspecting a pellicle that is part of a mask assembly. Dimensional reduction is becoming increasingly difficult in advanced technology nodes. Lithography uses increasingly shorter exposure wavelengths, including deep ultraviolet (DUV; approximately 193 nm to 248 nm), extreme ultraviolet (EUV; approximately 10 nm to 100 nm; particularly 13.5 nm), and X-rays (approximately 0.01 nm to 10 nm), to ensure accurate patterning in reduced dimensions. In an EUV scanner, EUV light is generated by a light source and reflected toward a wafer by multiple mirrors and a reflective mask. Only a portion of the EUV light reaches the wafer, so increasing the intensity of the EUV light generated by the light source is a topic of great interest.

[0092] In extreme ultraviolet (EUV) lithography, the pattern of a mask or reticle is reflected toward the wafer to expose and print the pattern onto the wafer. Due to the absorption of extreme ultraviolet light, the EUV scanner chamber is a vacuum environment. Particles in the EUV scanner chamber can freely transfer to the pattern-carrying surface of the reticle, forming reticle defects and causing pattern failure in all exposed areas. The pellicle can be a thin film of nanometer thickness that is transparent to EUV wavelengths. Mounting the pellicle at a selected distance from the reticle can prevent reticle defects formed by particles released from the tool. The distance from the reticle to the reticle is selected to be far enough away from the focal plane of the reticle so that any particles on the outer surface of the pellicle (e.g., the surface of the pellicle facing away from the reticle) will not cause pattern failure, as long as the particle size and EUV transparency are small and clear, respectively.

[0093] The pellicle helps prevent certain particles from depositing on the reticle. However, particles on the outer surface of the pellicle (e.g., the surface facing away from the reticle) may reduce the power of the extreme ultraviolet (EUV) light, thereby increasing the cycle time. In another example, pattern failures may still occur due to particles in the inner area of ​​the pellicle, which are called "inner on-pellicle defects" (IOPDs / IOPD). IOPDs can be formed in a variety of ways. For example, IOPDs may be formed during the thin film process of forming the pellicle or when it is installed to the mask assembly. After the pellicle is installed, IOPDs can easily fall onto the mask, such as during wafer processing.

[0094] Even with significant effort put into improving the cleanliness of the mounting process (e.g., increased mask cleaning, pellicle particle inspection, mounting tool and environmental cleaning, etc.), particles are still present on the pellicle in approximately 1% of cases. For example, an inspection process for pellicle quality may be performed before the pellicle is installed. After the pellicle is installed, it may not be possible to use a reticle inspection tool because the pellicle, which is under tension, can be easily torn by fluctuations and external vibrations. An effective way to identify IOPD after mounting is to perform wafer exposure and check if pattern failure occurs. However, this can reduce yield due to the number of wafers sent for wafer defect inspection. Wafer defect inspection tools may also be overused due to IOPD detection and reduce availability for other inspection tasks. Once IOPD is attached to the pattern surface, increased batch sizes can lead to further reductions in yield.

[0095] In an embodiment of the present disclosure, a method of scanning a pellicle in situ (e.g., within an installer) is described. The method may be performed by scanning the pellicle using an optical imager mounted on a mask stage as the pellicle moves to a mating position. When a particle is detected on the pellicle, the pellicle can be removed from the lithography apparatus for replacement or rework, thereby reducing tool downtime. The embodiments of the present disclosure provide real-time scanning and particle gating prior to final mounting operations. Thus, not only particles on the mask surface but also particles on the inner film of the pellicle can be identified. The size of particles less than about 2 microns (μm) and their location can be determined. When a particle is detected on the pellicle, another clean pellicle can be attached. In some embodiments, a second optical imager mounted on the pellicle may scan the mask surface in a similar manner to look for particles. In response to detecting a particle on the mask, the mask can be cleaned. Thus, dropped particles and rework process problems can be avoided, thereby reducing tool downtime and increasing throughput.

[0096] Figure 1A and 1B A photolithography exposure system 10 is depicted according to various embodiments. The detailed description of the photolithography exposure system 10 is intended to provide a FIG. 6A to FIG. 7 Context for description of the relevant particle detection process.

[0097] Figure 1A1 is a schematic diagram and diagrammatic view of a lithography exposure system 10 according to certain embodiments. In certain embodiments, the lithography exposure system 10 is an extreme ultraviolet (EUV) lithography system designed for exposing a photoresist layer by EUV radiation, and may also be referred to as an EUV system 10. The EUV system 10 may also be referred to as an EUV scanner or a lithography scanner. The lithography exposure system 10 includes a light source 120, an illuminator 140, a mask stage 16, a projection optics module (or projection optics box (POB)) 180, and a substrate stage 24, according to certain embodiments. Components of the lithography exposure system 10 may be added or omitted, and the disclosure should not be limited by the embodiments.

[0098] The light source 120 is configured in some embodiments to generate light radiation having a wavelength range between about 1 nm and about 100 nm. In a specific example, the light source 120 generates EUV radiation having a wavelength centered at about 13.5 nm. Therefore, the light source 120 is also referred to as an EUV radiation source. However, it should be understood that the light source 120 should not be limited to emitting EUV radiation. The light source 120 can be used to perform any high intensity photon emission from exciting the target fuel.

[0099] In various embodiments, the illuminator 140 includes various refractive optical components, such as a single lens or a lens system with multiple reflectors 100, such as a lens (wave zone plate) or alternative reflective optical components (for EUV lithography exposure systems), such as a single mirror or a mirror system with multiple mirrors, to direct light from the light source 120 to the mask stage 16, and in particular to the mask 18 fixed to the mask stage 16. In embodiments where the light source 120 generates light in the EUV wavelength range, a reflective optical component is used. In some embodiments, the illuminator 140 includes at least two lenses, at least three lenses, or more.

[0100] The mask stage 16 is designed to hold the mask 18. In some embodiments, the mask stage 16 includes an electrostatic chuck (e-chuck) to hold the mask 18. One benefit of using an electrostatic chuck is that gas molecules absorb extreme ultraviolet (EUV) radiation, and the electrostatic chuck can be operated in an EUV lithography patterning exposure system that maintains a vacuum environment to avoid loss of EUV intensity. In the present disclosure, the terms mask, photomask, and reticle are used interchangeably. In the current embodiment, the mask 18 is a reflective mask. An example structure of the mask 18 includes a substrate of a suitable material, such as a low thermal expansion material (LTEM) or fused quartz. In various examples, the LTEM includes doped SiO2 TiO 2 , or other suitable materials with low thermal expansion. Mask 18 includes a reflective multilayer deposited on a substrate. Mask stage 16 can move in two horizontal directions, such as the X-axis direction and the Y-axis direction, so as to expose multiple different areas of semiconductor wafer 22 to light in the pattern generated by mask 18. Semiconductor wafer 22 may have a mask layer 26 thereon, which may be a photoresist layer that is sensitive to light with the pattern of mask 18.

[0101] The projection optical module (or projection optical box (POB)) 180 is configured to image the pattern of the mask 18 onto the semiconductor wafer 22 fixed on the substrate stage 24 of the lithography exposure system 10. In some embodiments, the POB 180 has a refractive optical component (e.g., for UV lithography exposure systems), or in various embodiments, has a reflective optical component (e.g., for EUV lithography exposure systems). Light directed from the mask 18, carrying an image of the pattern defined on the mask, is collected by the POB 180. The illuminator 140 and the POB 180 are collectively referred to as an optical module of the lithography exposure system 10. In some embodiments, the POB 180 includes at least six reflective optical components.

[0102] In some embodiments, the semiconductor wafer 22 may be made of silicon or other semiconductor materials. Alternatively, the semiconductor wafer 22 may also include other basic semiconductor materials, such as germanium (Ge). In some embodiments, the semiconductor wafer 22 is made of compound semiconductors, such as silicon carbide (SiC), gallium arsenide (GaAs), indium arsenide (InAs), or indium phosphide (InP). In some embodiments, the semiconductor wafer 22 is made of alloy semiconductors, such as silicon germanium (SiGe), silicon germanium carbon (SiGeC), gallium arsenic phosphide (GaAsP), or gallium indium phosphide (GaInP). In some other embodiments, the semiconductor wafer 22 may be a silicon-on-insulator (SOI) or a germanium-on-insulator (GOI) substrate.

[0103] In addition, the semiconductor wafer 22 may have various device components. Examples of device components formed in the semiconductor wafer 22 include transistors (e.g., metal oxide semiconductor field effect transistors (MOSFET), complementary metal oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJT), high voltage transistors, high frequency transistors, P-channel and / or N-channel field-effect transistors (PFETs / NFETs), etc.), diodes and / or other applicable components. Various processes are performed to form device components, such as deposition, etching, implantation, photolithography, annealing and / or other suitable processes. In some embodiments, the semiconductor wafer 22 is coated with a solder mask layer that is sensitive to EUV radiation. The various components described above are integrated together and can perform photolithography processes.

[0104] The photolithography exposure system 10 may further include other modules, or be integrated (or coupled) with other modules, such as a cleaning module, which is designed to provide hydrogen to the light source 120. The hydrogen helps to reduce contamination in the light source 120. For further description of the light source 120, please refer to Figure 1B .

[0105] like Figure 1B As shown, according to some embodiments, the light source 120 is presented in the form of a schematic diagram. In some embodiments, the light source 120 uses a dual-pulse laser produced plasma (LPP) mechanism to generate plasma 88 and further generate EUV radiation from the plasma. The light source 120 includes a droplet generator 30, a droplet receiver 35, a laser generator 50, a laser produced plasma (LPP) collector 60, a monitoring device 70 and a controller 90. Some or all of the above components of the light source 120 may be performed under vacuum. It should be understood that the components of the light source 120 can be added or omitted and should not be limited by the embodiments.

[0106] The droplet generator 30 is configured to generate a plurality of droplets 82, which may be elongated, and to generate the target fuel 80 to an excitation region where at least one laser pulse 51 from the laser generator 50 hits the droplet 82 on the x-axis, such as Figure 1BAs shown. In one embodiment, the target fuel 80 includes tin (Sn). In one embodiment, the droplet 82 can be formed into an elliptical shape. In one embodiment, the droplet 82 is generated at a rate of about 50 kilohertz (kHz) and introduced into the excitation area of ​​the light source 120 at a speed of about 70 meters per second (m / s). Other materials can also be used for the target fuel 80, for example, a liquid material containing tin, such as a eutectic alloy containing tin, lithium (Li) and xenon (Xe). The target fuel 80 in the droplet generator 30 can be in a liquid phase.

[0107] The laser generator 50 is configured to generate at least one laser pulse to convert the droplet 82 into plasma 88. In some embodiments, the laser generator 50 is configured to generate a laser pulse 51 toward the illumination point 52 to convert the droplet 82 into plasma 88 that generates EUV radiation 84. The laser pulse 51 passes through a window (or lens) 55 and illuminates the droplet 82 at the illumination point 52. The window 55 is formed in the segmented collector 60 and is made of a suitable material that is substantially transparent to the laser pulse 51. The droplet receiver 35 captures and collects unused droplets 82 and / or divergent materials of the droplet 82 generated by the laser pulse 51 hitting the droplet 82.

[0108] The plasma emits EUV radiation 84, which is collected by the collector 60. The collector 60 further reflects and focuses the EUV radiation 84 for a lithography process performed by an exposure tool. In some embodiments, the collector 60 has an optical axis 61 that is parallel to the z-axis and perpendicular to the x-axis. As shown, the collector 60 may include a single portion, or at least two portions offset from each other in the z-axis direction. The collector 60 may further include a container wall 65 having a first pump 66 and a second pump 68. In some embodiments, the first pump 66 and the second pump 68 include a scrubber configured to remove particles and / or gases from the collector 60. The first pump 66 and the second pump 68 may be collectively referred to herein as "pumps 66, 68".

[0109] In one embodiment, the laser generator 50 is a carbon dioxide (CO 2 ) laser source. In some embodiments, the laser generator 50 is used to generate laser pulses 51 having a single wavelength. The laser pulses 51 are transmitted through an optical component to focus and determine the angle of incidence of the laser pulses 51. In some embodiments, the laser pulses 51 have a spot size of about 200 microns to 300 microns, for example, 225 microns. The laser pulses 51 are generated to have a certain drive power to meet wafer production goals, such as a yield of 125 wafers per hour (WPH). For example, the laser pulses 51 are equipped with a drive power of about 23 kilowatts. In various embodiments, the drive power of the laser pulses 51 is at least 20 kilowatts, for example, 27 kilowatts.

[0110] The monitoring device 70 is configured to monitor one or more conditions in the light source 120 to generate data for controlling configurable parameters of the light source 120. In some embodiments, the monitoring device 70 includes a measuring tool 71 and an analyzer 73. In the case where the measuring tool 71 is configured to monitor the conditions of the droplets 82 supplied by the droplet generator 30, the measuring tool may include an image sensor, such as a charge coupled device (CCD), a complementary metal oxide semiconductor sensor (CMOS), or a similar device. The measuring tool 71 generates a monitoring image including an image or video of the droplets 82 and transmits the monitoring image to the analyzer 73. In the case where the measuring tool 71 is configured to detect the energy or intensity of EUV light 84 generated by the droplets 82 in the light source 12, the measuring tool 71 may include multiple energy sensors. The energy sensor can be any suitable sensor capable of observing and measuring electromagnetic radiation energy in the ultraviolet region.

[0111] The analyzer 73 is configured to analyze the signal generated by the measuring tool 71 and output a detection signal to the controller 90 according to the analysis result. For example, the analyzer 73 includes an image analyzer. The analyzer 73 receives the image-related data transmitted from the measuring tool 71 and performs image analysis processing on the image of the droplet 82 in the excitation area. Then, the analyzer 73 sends the data related to the analysis to the controller 90. The analysis may include flow path error or position error.

[0112] In some embodiments, two or more measurement tools 71 are used to monitor different conditions of the light source 120. One of them is configured to monitor the condition of the droplets 82 supplied by the droplet generator 30, and the other is configured to detect the energy or intensity of the EUV light 84 generated by the droplets 82 in the light source 120. In some embodiments, the measurement tool 71 is a final focus module (FFM) and is located in the laser source 50 to detect the light reflected from the droplets 82.

[0113] The controller 90 is configured to control one or more components of the light source 120. In some embodiments, the controller 90 is configured to drive the droplet generator 30 to generate the droplets 82. In addition, the controller 90 is configured to drive the laser generator 50 to emit laser pulses 51. The generation of the laser pulses 51 may be controlled by the controller 90 to be associated with the generation of the droplets 82 so that the laser pulses 51 hit each target (droplet 82) in sequence.

[0114] In some embodiments, the droplet generator 30 includes a liquid reservoir 31 and a nozzle assembly 32. The liquid reservoir 31 is configured to contain a target substance 80. In some embodiments, a gas line 41 is connected to the liquid reservoir 31 for introducing a pump gas such as argon from a gas source 40 into the liquid reservoir 31. By controlling the gas flow rate in the gas line 41, the pressure in the liquid reservoir 31 can be manipulated. For example, when the gas is continuously supplied to the liquid reservoir 31 through the gas line 41, the pressure in the liquid reservoir 31 increases. Therefore, the target substance 80 in the liquid reservoir 31 can be forced to be discharged from the liquid reservoir 31 in the form of drops 82.

[0115] Figures 2A to 2C Views of various embodiments of a mask assembly 200 for a lithography scanner are shown in accordance with various aspects of the present disclosure. Figure 2A is a side view of the mask assembly 200 . Figure 2B is a top view of the mask pattern 230 of the mask assembly 200 . Figure 2C is a graph illustrating exposure errors in region 225 of semiconductor wafer 220 . Figures 2A to 2C Detailed description for reference FIG. 6A to FIG. 7 The context of the process of detecting particles described in .

[0116] exist Figure 2A In the embodiment, the mask assembly 200 includes a mask stage 216 and a mask 218 attached thereto. The mask stage 216 and the mask 218 may be Figure 1A and 1B The mask stage 16 and the mask 18 are provided. The mask 218 includes a mask pattern 230, which may be located in a layer of the mask 218 facing the reflector of the illuminator 140 and the POB 180 located on both sides of the mask assembly 200.

[0117] Particles 250 may be present in a lithography scanner. Particles 250 may include different types of particles generated by different sources in the lithography scanner. For example, particles 250 may include tin particles generated by light source 120 during formation of plasma 88. Particles 250 may include SiC particles generated due to movement of mask assembly 200 in the X-axis and Y-axis directions. Particles 250 may include carbon particles generated by a pod or carrier used to transport mask 218 in and out of the lithography scanner. Other particles 250 may be generated by other sources inside or outside the lithography scanner and have different material compositions. One or more of the particles 250 may be deposited on the surface of mask 218, particularly on one or more mask pattern areas of mask pattern 230. Particles 250 deposited on the surface of the reticle form reticle defects, which may cause all exposed areas of the chip (for example, Figure 2C The pattern in area 225) fails.

[0118] Figure 2B A view of a mask pattern 230 with particles 250 is shown. The mask pattern 230 is exposed to the internal environment of a lithography scanner. When the mask assembly 200 is in the lithography scanner, the particles 250 may land on the mask 218. The particles 250 may form shorts or bridges or merges between one or more pattern areas of the mask pattern 230. When the pattern of the mask 218 is transferred to a semiconductor wafer, electrical defects such as shorts or bridges or merges may be generated between features of the semiconductor wafer. For example, adjacent semiconductor fins or adjacent conductive lines may be inadvertently merged, which may cause failure of an integrated circuit chip formed in the semiconductor wafer.

[0119] Figure 2C A schematic diagram of a semiconductor wafer 220 is shown, which may be Figure 1A and 1B The semiconductor wafer 22 is in the embodiment of the present invention. Figure 2C The view may be a diagram of an image generated by a metrology tool analyzing semiconductor wafer 220. During the exposure process, light carrying mask pattern 230 is irradiated onto semiconductor wafer 220, and particles 250 change the pattern, which is repeatedly transferred to a portion or all of region 225 of semiconductor wafer 220. As a result, the quality of semiconductor wafer 220 is reduced, which reduces the productivity of the lithography scanner.

[0120] Figures 3A to 3G 2 is a schematic diagram showing that a protective film 370 and a frame 360 ​​are installed on the mask assembly 200 to prevent particles 250 from being attached to the mask 218. Figure 3A and 3B In the embodiment, the pellicle 370 is suspended above the mask pattern 230 by the frame 360. The pellicle 370 may be a nanometer-thick film with high transparency (e.g., >90%) to EUV wavelength (e.g., 13.5 nm). For example, the thickness of the pellicle 370 in the Z-axis direction may be in the range of about 1 nm to about 10 nm.

[0121] The frame 360 ​​has a height D1, which may be in the range of about 1 mm to about 3 mm, or greater. The height D1 is substantially the same as the separation distance between the protective film 370 and the mask pattern 230 in the Z-axis direction. Figure 3BAs shown, the frame 360 ​​may have a rectangular (e.g., square) shape on the XY plane. As shown, the frame 360 ​​may be adjacent to the mask pattern 230 on four sides. The frame 360 ​​may be horizontally offset from the mask pattern 230 in the X-axis and Y-axis directions. For example, the frame 360 ​​may be offset from the mask pattern in the Y-axis direction by a second distance D2 and offset in the X-axis direction by a third distance D3. The height D1, the distance D2, and the distance D3 may be the same as each other. In some embodiments, one or more of the height D1, the distance D2, and the distance D3 are different from the others. For example, the height D1 may be in the above-mentioned range of about 1 mm to 3 mm, while the second distance D2 and the third distance D3 may be in the range of about 0.5 mm to about 10 mm. Mounting the protective film 370 on the frame 360 ​​can prevent mask defects formed by particles released by the lithography scanner. Generally, height D1 is large enough that any particle 250 smaller than a selected size (eg, smaller than about 500 nanometers in diameter) that lands on the outer surface of pellicle 370 is far enough away from the focal plane of the incident light that the particle 250 does not cause a pattern defect failure.

[0122] Figure 3C The presence of particles 370S and 370L on the protective film 370 is shown. The particles 370S and 370L may include small particles 370S and large particles 370L. The small particles 370S may have a diameter D4 that is smaller than the particle detection resolution of the inspection tool, while the large particles 370L may have a diameter D5 that is larger than the particle detection resolution. The particles 370S and 370L may be the same as those described above with reference to FIG. FIG. 2A to FIG. 2C The particles 250 described are the same. Before the pellicle 370 is installed on the mask assembly 200, an inspection process may be performed by an inspection tool to verify the quality of the pellicle. The verification process may have a particle detection range or resolution, and particles beyond this range or resolution may not be identified. For example, the particle detection resolution may be approximately 300 nanometers. The diameter D4 of the small particle 370S may be less than 300 nanometers, such as less than 200 nanometers, less than 100 nanometers, less than 50 nanometers, or the like. The diameter D5 of the large particle 370L may be greater than 300 nanometers. Therefore, the large particles 370L on the inner and outer surfaces of the pellicle 370 may be identified by the inspection tool, while the small particles 370S may not be identified by the inspection tool and may remain on the pellicle 370 when installed.

[0123] After the pellicle 370 is installed, since the pellicle 370 is in a tight state, it is easily broken by waves and external vibrations, and therefore, further inspection by an inspection tool may damage the pellicle 370. Therefore, small particles 370S may still exist on the inner and outer surfaces of the pellicle 370 after the pellicle 370 is installed on the mask assembly 200.

[0124] Figure 3D The mask assembly 200 with the pellicle 370 attached is shown after a period of operation. Generally, the pellicle 370 can be operated for a selected number of wafers before being replaced. For example, the pellicle 370 can be said to have a "lifetime" of approximately 10,000 wafers, approximately 15,000 wafers, etc. In another example, the lifespan of the pellicle 370 may be measured in terms of the number of moves or transitions. Exposure of all areas of a single wafer may include tens, hundreds, or thousands of moves. When manufacturing integrated circuit chips on the semiconductor wafer 220, the mask assembly 200 may be moved back and forth along the XY plane, and particles 350T, particles 350P may be attached to the outer surface of the pellicle 370, such as Figure 3D Particles 350T and 350P may include tool particles 350T and pod particles 350P, as well as the above-mentioned reference particles. FIG. 2A to FIG. 2C Other particle types described. Over time, as particles 350T, particles 350P accumulate on pellicle 370, and due to repeated acceleration of pellicle 370 in the XY plane, pellicle 370 may deform or crack and need to be replaced.

[0125] One or more internal particles or "internal pellicle defects (IOPDs)" 350I may be located on the inner surface of pellicle 370 facing mask 218. Figure 3C As described in reference to , internal particles 350I may be small particles 350S that are present on pellicle 370 and are still present before and after installation. For example, IOPD 350I may be formed during the thin film process of forming pellicle 370, or may be induced when pellicle 370 is installed on mask 218. In another example, internal particles 350I may be generated due to bond breakage of pellicle elements after EUV exposure. In another example, internal particles 350I may be tool particles 350T or pod particles 350P that enter the space between frame 360, pellicle 370 and mask 218, which is in the process of EUV exposure. Figure 3E and Figure 3F A more detailed description is given in the reference.

[0126] Figure 3E and Figure 3F Depicts a side view of the frame 360 ​​( Figure 3E ) and internal film defects due to openings or holes 362 in the frame 360 ​​( Figure 3F). Since the pellicle 370 operates in a vacuum or near-vacuum environment, the holes 362 present in the frame 360 ​​help balance the pressure between the space below the pellicle 370 and the internal environment of the lithography scanner equipped with the mask assembly 200. Without the holes 362, after the pellicle 370 is mounted to the mask 218, the pellicle 370 may be easily broken in a vacuum or near-vacuum environment due to the air pressure below the pellicle 370 on the air pressure of the space between the thin pellicle 370 and the mask pattern 230.

[0127] like Figure 3F As shown, due to the holes 362 in the frame 360, the particles 350 may enter the space between the pellicle 370 and the mask pattern 230 through the holes 362. The particles 350 may be deposited on the inner surface of the pellicle 370, and then may fall and be deposited on the mask pattern 230. Figure 3F The particle 350 shown in FIG. 1 may be referred to as an “internal pellicle defect.” Internal pellicle defects are difficult to detect and may result in significant reduction in yield.

[0128] FIG. 3G is a schematic diagram illustrating the loss of output power of light incident on semiconductor wafer 220 as the number of times mask assembly 200 is moved during processing of the wafer. For example, the output power of light source 120 may be approximately 250 watts, and after mask assembly 200 is moved 20,000 times, the effective output power may decrease by approximately 5% to approximately 238 watts due to particles accumulated on pellicle 370. As shown in FIG. 3G, the attenuation of pellicle 370 may vary significantly from pellicle to pellicle, batch to batch, etc., which may increase the difficulty of estimating the output power and controlling (e.g., compensating for) the reduction in output power relative to the number of moves. For example, if the output power attenuation during the life of pellicle 370 is known, the exposure time may be increased based on the attenuation relative to the number of moves.

[0129] Figure 4 Methods of attaching a pellicle to a mask assembly according to various embodiments are described. Figure 4 The method is described as provided with reference FIG. 6A to FIG. 7 The context in which the process is related.

[0130] In operation 410, a mask assembly having a pellicle assembly is formed. Operation 410 includes operation 411 and operation 412. The mask assembly in operation 410 may be an embodiment of the mask assembly 200, may be similar or identical to the mask assembly 200, and is described using the same reference numerals as above. In operation 411, a mask 218 having a mask pattern 230 and a pellicle assembly including a frame 360 ​​and a pellicle 370 are provided. The pellicle 370 may have one or more particles 350. For example, as shown in operation 411, the particles 350 are located on the inner surface of the pellicle 370. In operation 412, as shown, the pellicle assembly is mounted to the mask assembly or mated with the mask assembly.

[0131] After forming the mask assembly with the pellicle assembly thereon in operation 410, the mask assembly with the pellicle assembly is inspected in operation 420. An optical inspection device is used in operation 420 to detect the presence of particles 350 on the inner and / or outer surfaces of the pellicle 370. When the number and size of particles on the pellicle 370 do not exceed a selected threshold, the process proceeds from operation 420 to operation 450, in which the mask assembly with the pellicle assembly is sent for use in a photolithography system, such as with reference to FIG. Figure 1A and 1B The photolithography system 10 is described. When the number and size of particles on the pellicle 370 exceeds a selected threshold, the process proceeds from operation 420 to operation 430 where removal of the particles is attempted.

[0132] When a particle of a size and / or quantity exceeding a selected threshold is detected on the pellicle 370, operation 430 is performed immediately after operation 420. In operation 430, an attempt is made to remove the particle from the pellicle 370. If the particle is successfully removed, the mask assembly with the pellicle assembly is qualified and may be sent for use in a lithography system, such as lithography system 10, in operation 450. When the removal of the particle is unsuccessful or insufficiently successful, the process proceeds from operation 430 to operation 440, where the mask assembly with the pellicle assembly is reworked.

[0133] When the particle removal on the mirror cover 370 in operation 430 fails, operation 440 is performed next. In the rework process, the pellicle assembly and the pellicle may be removed from the mask assembly and the pellicle may be cleaned a second time. In some embodiments, the pellicle is replaced with a new pellicle by removing the pellicle and fixing the new pellicle to the frame.

[0134] After operation 440, the process proceeds to operation 412 where the pellicle assembly is mounted to the mask assembly as previously described.

[0135] like Figure 4 The process shown facilitates delivering a mask assembly with a pellicle assembly attached and with little or no particles thereon. Figure 7 The detailed process 701 depicted in FIG. 4 includes installing one or more optical sensors in the installer to speed up the detection of particles on the pellicle, the mask, or both. In the detailed process 701, particles can be detected before the pellicle assembly is installed on the mask assembly, which may help reduce or eliminate rework in the rework process of operation 440. 6A to 6F The operation of process 701 is described. FIG. 5A to FIG. 5D The following description provides context for the structural elements and process operations that may be performed by process 701.

[0136] Figure 5A Operation 511A of forming a mask pattern 230 on a mask 218 according to various embodiments and operation 511B of storing the mask 218 in a standard mechanical interface (SMIF) pod 514 are depicted. In making a mask for EUV lithography, such as mask 218, a number of operations may be performed in operation 511A. Forming an EUV mask may initially include providing a blank substrate 518 made of fused silica or other suitable material. The substrate 518 may be polished to be very flat and clean, which is beneficial for achieving accuracy and resolution in the final mask. An absorber or metal layer 230 may be deposited as a thin layer of metal (e.g., molybdenum) on the substrate 518. The metal layer 230 absorbs EUV light and forms a pattern that may be transferred to a wafer during semiconductor processing. After the absorber layer 230 is deposited, a layer of photoresist (not depicted) is coated on its surface. The photoresist layer is then exposed to a pattern of light, which causes the photoresist to become more soluble or less soluble in certain areas. The photoresist is developed, which removes the easily soluble areas, leaving a patterned photoresist layer on the absorber layer. The patterned photoresist layer can be used as a mask for etching the absorber layer. For example, a plasma etcher 513 is used to selectively remove the exposed areas of the absorber layer, which leaves the desired pattern. The patterned metal layer 230 is also referred to as a "mask pattern" 230. The substrate 518 and the mask pattern 230 can be collectively referred to as a mask 218.

[0137] Immediately after forming the mask pattern 230 in operation 511A, in operation 511B, the mask 218 is placed in the SMIF pod 514, as shown. Prior to placing the mask 218 in the SMIF pod 514, the mask may be cleaned by a cleaner or cleaning equipment (not depicted).

[0138] Figure 5BOperation 511C and operation 511D are shown. Operation 511C is followed by operation 511B. In operation 511B, after the mask 218 is placed in the SMIF pod 514, the SMIF pod 514 is transferred to the mounter or mounting device 530, and the mask 218 is transferred from the SMIF pod 514 to the mask stage 522. The mask stage 522 is an embodiment of the mask stage 16 and the mask stage 216, and may be similar thereto in many respects. In operation 511C, the mask 218 is mounted to the mask stage 522, for example, by a robot 520, which may include a robot arm 520. The robot 520 can remove the mask 218 from the SMIF pod 514 and can place the mask 218 on the mask stage 522, after which the robot 520 can release the mask 218. The mask stage 522 may be located at a top portion 538 of the mounting apparatus 530 , while the pellicle stage 532 may be located at a bottom portion 536 of the mounting apparatus 530 .

[0139] Operation 511D is followed by operation 511C. After the mask 218 is positioned on the mask stage 522, the mask stage 522 may be moved in the mounter 530 to a mask loading position or a mask docking position (see Figure 5C ),like Figure 5B As shown by the arrow shown in. The loading position may be aligned with the protective film loading position or the protective film docking position of the protective film station 532.

[0140] Figure 5C Operation 511E and operation 511F are depicted. Operation 511E is performed after operation 511D. In operation 511D, after the mask stage 522 is moved to the mask mounting position, the pellicle assembly 542 including the pellicle mounted on the frame described previously is transferred from the pellicle box 540 to the pellicle table 532. Operation 511E may be performed by the robot 520. For example, the robot 520 may grasp the pellicle box 540, open the lid of the pellicle box 540, take out the pellicle assembly 542 from the pellicle box 540, and place the pellicle assembly 542 on the pellicle table 532.

[0141] Operation 511F is followed by operation 511E. In operation 511E, after the film assembly 542 is transferred from the film box 540 to the film assembly 542, as shown in FIG. Figure 5C As shown by the arrow in FIG. 5 , the pellicle assembly 542 may be moved to a pellicle mounting position or a pellicle mating position (see FIG. 5 ) below the mask stage in operation 511F. Figure 5D ).

[0142] Figure 5D Operation 511G is depicted immediately following operation 511F. In operation 511G, pellicle stage 532 is slowly raised until pellicle assembly 542 is mounted on mask 218.

[0143] In reference FIG. 5A to FIG. 5D In the described process, each of operations 511A to 511G may generate particles within the mask 218 or the pellicle. 6A to 6F and Figure 7 A process 701 is depicted, which is performed before the pellicle assembly 542 is assembled to the mask 218 (e.g., before Figure 5D 511G) to detect particles on the pellicle assembly 542 or the mask 218. One or more in-situ surface scans detect particles and verify the quality of the mask before the pellicle assembly 542 is assembled to the mask 218, for example, by detecting whether the defect level (e.g., the number of defects) of the pellicle assembly 542 and / or the mask 218 is less than a selected value. Process 701 may prevent the presence of dropped particles inside the pellicle assembly 542 or on the surface of the mask 218 after the pellicle assembly 542 is assembled to the mask 218.

[0144] Figure 7 is a flow chart of a process or method 701 for forming a device according to various embodiments. In some embodiments, the process 701 for forming a device includes multiple operations (e.g., operation 700, operation 710, operation 720, operation 722, operation 724, operation 730, operation 740, operation 750, operation 760, operation 762, operation 764, operation 770, operation 772, operation 774, and operation 780). The process 701 for forming a device is further described according to one or more embodiments. It should be noted that the operations of process 701 may be rearranged or otherwise modified within the scope of various aspects. It should also be noted that additional processes may be provided before, during, and after process 701, and some other processes may only be briefly described here. In some embodiments, process 701 is referred to as 6A to 6F The described installation system 500 performs. 6A to 6F and FIG. 5A to FIG. 5D , but the process 701 can be performed by a mounting system having one or more structural elements different from the mounting system 500. It should be understood that the operation 780 of performing a semiconductor process using a mask module can be performed by the reference numeral 780. Figure 1A and Figure 1B The process 701 is performed by the photolithography exposure system 10 described above. Process 701 can be performed by one or more processors executing computer instructions. In some embodiments, process 701 is performed by specially designed hardware. In some embodiments, process 701 is performed by a combination of hardware and software.

[0145] Method 701 begins at operation 700 and proceeds to operation 710, where a mask is attached to a mask stage. The mask may be Figure 5B Attach to the mask stage in a manner similar to that described in operation 511C. Fig. 6A , mask 218 has been shown attached to mask stage 522 .

[0146] Operation 720 is subsequent to operation 710. After the mask is attached to the mask stage in operation 710, the mask stage is moved to a mask loading position in operation 720, such as Fig. 6A As shown by the arrow in Figure 6B The mask loading position may be different from the reference Figure 5B The operation 511D is similar to that described in FIG.

[0147] Operation 722 follows operation 720. In operation 722, it is determined whether the mask stage has reached the mask mounting position. When the mask stage has not reached the mask mounting position, method 701 proceeds from operation 722 to operation 724, where the mask is scanned by a first optical detector (eg, a first interferometer).

[0148] Fig. 6A and 6B A first optical detector 600 is depicted. In some embodiments, the first optical detector 600 is an interferometer. For example, the first optical detector 600 may be a Spectral Domain Optical Coherence Tomography (SD-OCT) imaging device. Fig. 6E One embodiment of a SD-OCT imaging device 600 is depicted and described in detail, and reference will be made to it later in detail.

[0149] like Fig. 6A As shown, the first optical detector 600 can be installed on one side of the film stage 532. Fig. 6A As shown, this side may be the side farther from the protective film installation position. In some embodiments, this side is the side closer to the protective film installation position. Fig. 6A and Figure 6B As shown, the first optical detector 600 may be oriented upward, facing the mask stage 522. Therefore, when the light for scanning the mask pattern 230 is emitted from the first optical detector 600, it may irradiate the mask pattern 230 while the mask stage 522 passes through the first optical detector 600 and goes to the mask mounting position.

[0150] In some embodiments, the light extends along an axis. Figure 6BAs shown by the arrow in , the mask stage 522 may move in a first direction toward the mask mounting position. The light may extend in a second direction perpendicular to the first direction. The width of the light along the second direction may be substantially the same as the width of the mask pattern 230 along the second direction.

[0151] In some embodiments, the width of the light in the second direction is much smaller than the width of the mask pattern 230 in the second direction. Therefore, the light emitted from the first optical detector 600 may scan back and forth in the second direction to cover substantially the entire width of the mask pattern 230 when the mask stage 522 moves to the mask mounting position.

[0152] The first optical detector 600 captures one or more images at different depths. It should be understood that "depth" refers to a third direction perpendicular to the first direction and the second direction described herein. The different depths when scanning the mask 218 may refer to depths on or above the surface of the mask 218 where the mask pattern 230 is located. In other words, the first optical detector 600 may not need to capture an image under the mask pattern 230 because particles generally do not appear behind the mask pattern 230, but appear on the top of the mask pattern 230, i.e., on the surface facing the first optical detector 600.

[0153] The images may be combined to determine whether the mask 218 passes inspection. For example, the mask 218 may pass inspection when no particles are detected on the mask 218, or the number and / or size (or "defect level") of particles on the mask 218 does not exceed (e.g., is less than) a mask particle threshold (or "selected value"). In some embodiments, the mask particle threshold is zero, corresponding to no particles detected on the mask 218. It should be understood that particles below the selected size may not be detected by combining the images captured by the first optical detector 600. Therefore, the mask 218 may not be free of particles, but may be free of particles exceeding a selected size. For example, the selected size may be a major diameter greater than 200 nanometers, greater than 300 nanometers, or greater than other suitable dimensions.

[0154] Operation 720, operation 722, and operation 724 may be repeated until the mask stage 522 reaches the mask mounting position. In some embodiments, operation 724 is performed only when the mask 218 is directly above the first optical detector 600, and operation 724 may not be performed after the mask 218 is completely scanned and the mask stage 522 is still moving toward the mask mounting position. When it is determined that the mask stage 522 has reached the mask mounting position, the procedure 701 moves from operation 722 to operation 730.

[0155] Operation 720, operation 722, and operation 724 are described as an embodiment in which the first optical detector 600 scans the mask 218 when the mask stage 522 moves to the mask mounting position, such as Fig. 6A That is, the first optical detector 600 is stationary when capturing the image of the mask 218, while the mask stage 522 moves to the mask mounting position. In addition, when the first optical detector 600 captures the image, the pellicle assembly 542 is not present on the pellicle stage 532.

[0156] In some other embodiments, the first optical detector 600A may be placed on one side of the pellicle stage 532 close to the pellicle mounting position, that is, Fig. 6A In such an embodiment, the first optical detector 600A may be in a moving state when capturing an image of the mask 218 on the mask stage 522 fixed in the mask mounting position. In other words, the first optical detector 600A may scan the mask 218 when the pellicle stage 532 moves toward the pellicle mounting position. Moreover, the pellicle assembly 542 is present on the pellicle stage 532 when the first optical detector 600A captures the image.

[0157] In some further embodiments, the first optical detectors 600, 600A are located on both sides (remote and proximal) of the pellicle stage 532. In such embodiments, the first optical detector 600 located remotely may scan the mask 218 when the mask stage 522 moves toward the mask mounting position, while the first optical detector 600A located proximal may scan the mask 218 when the pellicle stage 532 moves toward the pellicle mounting position. The two scan results of the first optical detectors 600, 600A on both sides of the pellicle stage 532 may be compared or combined to determine the number, size, and location of particles on the mask 218.

[0158] When the mask stage 522 reaches the mask mounting position, operation 730 is performed following operation 722. In operation 730, it is determined whether the mask 218 passes the inspection. When it is determined that the mask 218 does not pass according to the image captured by the first optical detector 600, the process 701 proceeds from operation 730 to operation 740. When it is determined that the mask 218 passes according to the image captured by the first optical detector 600, the process 701 proceeds from operation 730 to operation 750.

[0159] Operation 740 is performed following operation 730 after determining that the mask 218 has failed the inspection. In operation 740, the mask 218 is cleaned. Cleaning the mask 218 may include: retracting the mask stage 522 from the mask mounting position to a position accessible by the robot 520, removing the mask 218 from the mask stage 522, placing the mask 218 in the SMIF pod 514, transporting the mask 218 to a cleaning device (not depicted), transferring the mask 218 from the SMIF pod 514 to the cleaning device and cleaning the mask 218 to remove particles thereon. After the mask 218 is cleaned, the mask 218 is reattached to the mask stage 522 by returning from operation 740 to operation 710.

[0160] After determining that the mask 218 passes inspection, operation 750 is performed following operation 730. In operation 750, the pellicle assembly including the pellicle is attached to the pellicle stage. For example, the pellicle assembly 542 is attached to Figure 6C Operation 750 may be similar in many respects to Figure 5C The operation of 511E is similar.

[0161] Operation 760 is performed after operation 750. In operation 750, after the film assembly 542 is fixed to the film stage, the film stage 532 moves to the film installation position, such as Figure 6C and 6D As indicated by the arrow in .

[0162] Operation 762 is followed by operation 760. In operation 762, it is determined whether the pellicle stage has reached the pellicle installation position. If the pellicle stage has not reached the pellicle installation position, process 701 proceeds from operation 762 to operation 764. If the pellicle stage has reached the pellicle installation position, process 701 proceeds from operation 762 to operation 770.

[0163] Operation 764 is subsequent to operation 762. In operation 764, in response to determining that the pellicle stage has not yet reached the pellicle installation position, or is only moving toward the pellicle installation position, the pellicle of the pellicle assembly 542 is scanned by the second optical detector 602. The second optical detector 602 may be similar in many respects to the first optical detector 600 and / or the first optical detector 600A. The scanning of the second optical detector 602 may be similar in many respects to that described with reference to operation 724, except that the scanning may be performed in depth on both sides of the pellicle. That is, as Figure 3D As described above, the pellicle may have particles on both the side facing the mask 218 and the side facing away from the mask 218. Therefore, images may be captured by the second optical detector 602 at depths above and below the pellicle.

[0164] like Figure 6CAs shown, the second optical detector 602 may be mounted on one side of the mask stage 522. This side may be a side away from the mask mounting position, such as Figure 6C As shown. Figure 6C and 6D As shown, the first optical detector 600 may be directed downward toward the pellicle stage 532. Therefore, when the pellicle stage 532 passes the second optical detector 602 on the way to the pellicle mounting position, the light used to scan the pellicle may hit the pellicle when leaving the second optical detector 602. Since the mask 218 is usually placed in the mounting device 530 before the pellicle assembly 542, another second optical detector 602 is usually not installed near the mask stage 522 because the pellicle is not present when the mask stage 522 moves to the mask mounting position.

[0165] These images may be combined to determine whether the pellicle has passed inspection. For example, the pellicle may pass inspection when no particles are detected on the pellicle, or the number and / or size (or "defect level") of particles on the pellicle does not exceed the pellicle particle threshold (or "selected value"). In some embodiments, the pellicle particle threshold is zero, corresponding to no particles detected on the pellicle. It should be understood that particles below the selected size may not be detected by combining the images captured by the second optical detector 602. Therefore, the pellicle may not be particle-free, but may be free of particles exceeding a selected size. For example, the selected size may be a major diameter greater than 200 nanometers, greater than 300 nanometers, or greater than other suitable sizes. In some embodiments, the pellicle may pass inspection when no particles are detected on the inner side of the pellicle (the side facing the mask 218). That is, the pellicle may pass inspection even if one or more particles are detected on the outer side of the pellicle (the side away from the mask 218).

[0166] After the pellicle stage 532 reaches the pellicle mounting position, operation 770 is performed following operation 762. In operation 770, it is determined whether the pellicle has passed the inspection. When it is determined that the pellicle has not passed according to the image captured by the second optical detector 602, the process 701 will proceed from operation 770 to operation 772. When it is determined that the pellicle has passed according to the image captured by the second optical detector 602, the process 701 will proceed from operation 770 to operation 774.

[0167] Operation 772 is performed following operation 770 after the pellicle inspection fails. In operation 772, the pellicle is replaced or reworked. For example, the pellicle can be removed by withdrawing the pellicle assembly from the pellicle mounting position, transferring the pellicle assembly to a pellicle box, transporting the pellicle assembly or pellicle to a cleaning device, cleaning the pellicle, and optionally reinstalling the pellicle on the frame for cleaning. In some cases, the pellicle is replaced with a new pellicle. For example, cleaning of the pellicle may not remove a sufficient number of particles from the pellicle. In another example, the pellicle may be damaged before or during cleaning. Therefore, a new pellicle may be installed on the frame instead of the pellicle with particles. After replacing or successfully reworking the pellicle, the pellicle assembly is reattached to the pellicle table in operation 750.

[0168] Operation 774 is performed subsequent to operation 770 in response to the pellicle passing the inspection. In operation 774, the pellicle assembly is mounted on the mask assembly. Mounting the pellicle assembly on the mask assembly may include multiple operations. A layer of adhesive may be applied to the edge of the mask assembly where the pellicle assembly will be attached. The adhesive may be a UV-curable adhesive that facilitates forming a tight bond between the mask assembly and the surface of the pellicle assembly. Pressure may be applied to the edge of the pellicle assembly to facilitate the pellicle assembly to adhere tightly to the mask assembly. The pressure may be applied using a vacuum suction cup (e.g., pellicle table 532) that holds the pellicle assembly in place when the pressure is applied. After the pellicle assembly is attached to the mask assembly, a UV light source may be used to cure the adhesive so that the adhesive hardens and adheres tightly to the mask assembly and the pellicle assembly surface.

[0169] Operation 780 is performed subsequent to operation 774. After the pellicle assembly is mounted to the mask assembly, the mask assembly with the pellicle assembly (or simply referred to as a "protected mask assembly") is used to perform one or more semiconductor processes. For example, the protected mask assembly can be installed in a lithography system (e.g., lithography system 10), and light may be reflected from mask 218 as patterned light, and the patterned light is directed to a photoresist layer on a semiconductor wafer. The photoresist layer is exposed to a pattern of patterned light, which makes the photoresist more soluble or less soluble in certain areas. The photoresist is developed, which removes the dissolved areas and leaves a patterned photoresist layer on the bottom layer. The patterned photoresist layer can be used as a mask for etching the bottom layer. Using, for example, a plasma etcher, an atomic layer etcher, or other suitable etcher, the exposed areas of the bottom layer are selectively removed, leaving the desired pattern.

[0170] Process 701 may be modified in various ways to form different embodiments. For example, operation 724 may be selective. That is, process 701 may only scan the pellicle. In another example, operation 764 may be selective. That is, process 701 may only scan the mask.

[0171] Fig. 6E One embodiment of a first optical detector 600 is depicted. Fig. 6E The depicted first optical detector 600 may also be an embodiment of the first optical detector 600A, an embodiment of the second optical detector 602, or both.

[0172] The first optical detector 600 may include an optical module 610 in a housing 612. The first optical detector 600 may include at least one motor capable of stepping the optical module 610 in a third axis direction, which may be a Z axis direction or a depth direction.

[0173] The optical module 610 includes a light source 620. The light source 620 may be or include one or more superluminescent diodes (SLDs) that emit near-infrared light.

[0174] The optical module 610 includes a beam splitter or interferometer 630. The interferometer 630 splits the light into two beams, one beam that is directed to the surface being imaged (e.g., mask 218 or pellicle) and the other beam that is reflected off a reference mirror 640. By measuring the time difference between the two beams of light that arrive at the detection sensor 650, the optical module 610 can determine the depth of each point on the surface.

[0175] The optical module 610 includes one or more mirrors 670 that direct light from the light source 620, the beam splitter 630, and the reference mirror 640 and back.

[0176] The optical module 610 includes a lens 680 located on the optical path between the light source 620, the beam splitter 630, the reference mirror 640 and the detection sensor 650. The optical module 610 further includes an objective lens 690 located between the beam splitter 630 and the imaged surface.

[0177] like Fig. 6E As shown, the optical module 610 may generate one or more images 652. Each image 652 may be captured at a different depth. With different Z-axis depths, a three-dimensional (3D) Z-axis interferogram 654 may be generated and a gating rule or algorithm may be used to find particles.

[0178] Fig. 6F The partial interference wave patterns 656 and 658 are shown, which are compared or combined Fig. 6E Waveform 658 is a visualization of waveform 656, which is a numerical representation of the depth of each relative area of ​​the surface captured by the image. Fig. 6FThe portions of the interference wave patterns 656, 658 depicted in FIG. 6A may correspond to regions having particles.

[0179] During the stage movement, the optical module 610 may scan various areas of the pellicle at various Z steps to identify particles, including particle size, particle location, and whether each particle is on the inner or outer surface of the pellicle.

[0180] Figure 8 is a flow chart describing a process 801 for scanning a mask and a pellicle before installation according to various embodiments. This process 801 can be used when two first optical detectors 600, 600A and a second optical detector 602 are present.

[0181] In operation 810, a mask is attached to a mask stage, which in many respects may be similar to Figure 7 The operation 710 is similar.

[0182] Operation 820 is a follow-up to operation 810. In operation 820, a first mask scan is performed. During the first mask scan, the pellicle stage is located in the pellicle mounting position, and the first optical detector 600 scans the mask 218 as the mask stage 522 moves to the mask mounting position. Operation 820 is similar in many respects to operation 810. Figure 7 The operation 724 is similar.

[0183] Operation 830 follows operation 820. After performing the first mask scan, the pellicle assembly is attached or mounted to the pellicle stage in operation 820, which is similar in many respects to the Figure 7 The operation 750 is similar.

[0184] Operation 840 is a follow-up to operation 830. After performing the first mask scan and securing the pellicle assembly to the pellicle stage, operation 840 performs a second mask scan and pellicle scan. The second mask scan and pellicle scan may be performed simultaneously as the pellicle stage moves toward the pellicle mounting position. For example, the first optical detector 600A may scan the mask 218 while the second optical detector 602 scans the pellicle.

[0185] Operation 850 is followed by operation 840. In operation 850, particles on the mask and pellicle are detected, which may be related to Figure 7 Operations 730 and 770 are similar. In process 801, particle detection on the pellicle does not have to be performed after or based on particle detection on the mask. Instead, particle detection on the pellicle can be performed simultaneously with particle detection on the mask, or can be performed before particle detection on the mask.

[0186] Embodiments may provide advantages: The method 701, 801 of the embodiment detects particles 350 before mounting the pellicle assembly to the mask assembly, which reduces rework and improves utilization.

[0187] According to at least one embodiment, a method includes: placing a mask on a mask stage; placing a pellicle assembly on the pellicle stage, the pellicle assembly including a pellicle; scanning the pellicle through a first optical detector to determine whether a defect level of the pellicle is less than a selected value; forming a protected mask assembly by mounting the pellicle assembly onto the mask assembly; and performing a semiconductor process using the protected mask assembly.

[0188] In accordance with at least one embodiment, scanning the reticle includes scanning the reticle by the first optical detector mounted on the mask stage.

[0189] According to at least one embodiment, the method further comprises: scanning the mask by a second optical detector mounted on the pellicle stage.

[0190] According to at least one embodiment, the method further comprises: capturing a plurality of images at the same depth by the second optical detector.

[0191] According to at least one embodiment, scanning the pellicle includes scanning the pellicle with the first optical detector when the pellicle assembly moves to the pellicle mounting position.

[0192] In accordance with at least one embodiment, when the pellicle assembly is moved to the pellicle mounting position, the first optical detector remains stationary in at least two axes.

[0193] According to at least one embodiment, the method further comprises: capturing a first plurality of images by the first optical detector, wherein a capture depth of at least one of the first plurality of images is different from a capture depth of another one of the first plurality of images.

[0194] According to at least one embodiment, an apparatus includes: a top portion; a mask stage disposed on the top portion; a bottom portion; a pellicle stage located on the bottom portion; and a second optical detector mounted on the mask stage, the second optical detector facing the pellicle stage.

[0195] According to at least one embodiment, the apparatus further comprises: a first optical detector mounted on the pellicle stage, the first optical detector facing the mask stage.

[0196] According to at least one embodiment, the device further comprises: a third optical detector mounted on the pellicle stage, wherein the third optical detector is located on a side of the pellicle stage opposite to the first optical detector.

[0197] According to at least one embodiment, the apparatus further comprises: a super brightness diode (SLD) that, in operation, directs light toward a surface of the pellicle mounted on the pellicle stage.

[0198] According to at least one embodiment, in operation, the second optical detector scans the pellicle when the pellicle stage moves along a first direction toward a pellicle mounting position, and the light has a width in a second direction perpendicular to the first direction, and the width is at least as large as a width of the pellicle.

[0199] In accordance with at least one embodiment, in operation, the second optical detector generates a second plurality of images by generating at least one first image at a first depth above the surface of the pellicle and generating at least one second image at a second depth below the surface of the pellicle.

[0200] According to at least one embodiment, in operation, the optical module of the second optical detector is stepped toward the first depth and the second depth during the generation of the second plurality of images.

[0201] According to at least one embodiment, a method includes: placing a mask assembly on a mask stage in a mounting device; placing a pellicle assembly on the pellicle stage in the mounting device; scanning the thin film assembly by a second interferometer located in the mounting device to generate a second set of multiple images; determining whether the number of particles on the pellicle of the pellicle assembly exceeds a threshold value; and in response to the number of particles not exceeding the threshold value: forming a protected mask assembly assembly by mounting the pellicle assembly onto the mask assembly; and performing a semiconductor process on a semiconductor wafer using the protected mask assembly.

[0202] According to at least one embodiment, the method further comprises: scanning a mask of the mask assembly with a first interferometer located in the mounting device to generate a first plurality of images.

[0203] According to at least one embodiment, the second interferometer is attached to one side of the mask stage.

[0204] According to at least one embodiment, the side is a side away from a mask mounting position.

[0205] According to at least one embodiment, the method further comprises: generating a three-dimensional interference wave pattern by combining the second plurality of images.

[0206] According to at least one embodiment, the method further comprises: determining a size and a position of at least one particle according to the interference wave pattern.

[0207] The foregoing summarizes the features of several embodiments so that the skilled person can better understand the various aspects of the present disclosure. The skilled person should understand that they can easily use the present disclosure as a basis for designing or modifying other processes and structures to achieve the same purpose and / or obtain the same advantages of the embodiments described herein. The skilled person should also be aware that such equivalent structures do not depart from the spirit and scope of the present disclosure, and they can make various changes, substitutions and modifications within this scope without departing from the spirit and scope of the present disclosure.

Claims

1. A photolithography system, characterized in that: include: Top part; a mask stage disposed on the top portion; bottom part; a film table located at the bottom portion; as well as A second optical detector is mounted on the mask stage, and the second optical detector faces the pellicle stage.

2. The lithography system according to claim 1, characterized in that: Also includes: A first optical detector is mounted on the pellicle stage.

3. The lithography system according to claim 2, characterized in that: The first optical detector faces the mask stage.

4. The photolithography system according to claim 2, characterized in that: Also includes: A third optical detector is mounted on the pellicle stage, the third optical detector being located on a side of the pellicle stage opposite to the first optical detector.

5. The photolithography system according to claim 1, characterized in that: Also includes: The superbrightness diode, in operation, directs light toward the surface of the pellicle mounted on the pellicle stage.

6. The photolithography system according to claim 5, characterized in that: in, In operation, the second optical detector scans the pellicle as the pellicle stage moves along a first direction toward a pellicle mounting position.

7. The photolithography system according to claim 6, characterized in that: The light has a width in a second direction perpendicular to the first direction, the width being at least as large as a width of the pellicle.

8. The photolithography system according to claim 1, characterized in that: in, In operation, the second optical detector generates at least one first image through a first depth above the surface of the pellicle.

9. The photolithography system according to claim 8, characterized in that: in, In operation, the second optical detector generates a second plurality of images by generating at least one second image at a second depth below the surface of the pellicle.

10. The photolithography system according to claim 9, characterized in that: in, In operation, the optical module of the second optical detector is stepped toward the first depth and the second depth during generation of the second plurality of images.

Images