Lithographic apparatus and method

Abstract

In an embodiment, a method includes heating a byproduct transport ring of an extreme ultraviolet source, the byproduct transport ring disposed below a leaf of the extreme ultraviolet source; after heating the byproduct transport ring for a first duration of time, heating the leaf; after heating the leaf, cooling the leaf; and after cooling the leaf for a second duration of time, cooling the byproduct transport ring. Embodiments of the present application provide lithographic apparatuses and methods.

Description

Technical Field

[0001] Embodiments of this application relate to lithography instruments and methods. Background Technology

[0002] As semiconductor devices continue to shrink, various processing techniques (e.g., photolithography) are adapted to allow the fabrication of devices with increasingly smaller dimensions. For example, as gate density increases, the fabrication processes for various components within the device (e.g., upper-layer interconnects) are adapted to be compatible with the overall device component reduction. However, as the process window for semiconductor processes becomes smaller, the fabrication of these devices has approached or even exceeded the theoretical limits of photolithography instruments. As semiconductor devices continue to shrink, the required spacing (i.e., pitch) between device elements is smaller than the pitch that can be fabricated using conventional optical masks and photolithography instruments. Summary of the Invention

[0003] In an embodiment, a photolithography method includes: heating a byproduct transport ring of an extreme ultraviolet (EUV) source, the byproduct transport ring being disposed below a blade of the EUV source; heating the blade after a first duration of heating the byproduct transport ring; cooling the blade after heating the blade; and cooling the byproduct transport ring after a second duration of cooling the blade.

[0004] In one embodiment, a photolithography method includes: generating plasma in a process chamber by bombarding tin droplets with a laser beam, wherein byproducts of the tin droplets are distributed on blades in the process chamber, and during plasma generation, the upper part of the blades has a higher temperature than the lower part of the blades; reducing the temperature difference between the upper and lower parts by heating the lower part of the blades; after reducing the temperature difference, melting the byproducts of the tin droplets on the blades by heating the upper and lower parts of the blades; and extracting the molten byproducts of the tin droplets from the process chamber.

[0005] In one embodiment, a photolithography instrument includes: a plasma generator; a light collector; a byproduct transport ring above the light collector, the byproduct transport ring including a first heating element; blades above the byproduct transport ring; a second heating element extending along the length of the blades; and a controller configured to: generate plasma above the light collector using the plasma generator, the plasma generating byproducts distributed on the blades; heat the first heating element of the byproduct transport ring to reduce the temperature difference between the upper and lower parts of the blades; and after reducing the temperature difference, heat the second heating element to melt the plasma distributed on the blades to generate byproducts. Attached Figure Description

[0006] When with attachment Figure 1When reading this document, the following detailed description is the best way to understand all aspects of this disclosure. It is worth noting that, in accordance with industry standard practice, the various parts are not drawn to scale. In fact, the dimensions of the various parts can be increased or decreased arbitrarily for clarity of discussion.

[0007] Figure 1 This is a block diagram of a photolithography system according to some embodiments.

[0008] Figures 2A-2B This is a detailed view of an extreme ultraviolet (EUV) source according to some embodiments.

[0009] Figures 3A-3C This is a partial view of a blade structure according to some embodiments.

[0010] Figure 4 This is a flowchart of a method for operating a photolithography system according to some embodiments.

[0011] Figure 5 This is a temperature chart of components of a lithography system during a cleaning process, according to some embodiments.

[0012] Figure 6 Experimental data for a lithography system according to some embodiments are shown. Detailed Implementation

[0013] The following disclosure provides numerous different embodiments or examples for implementing various components of the described subject matter. Specific examples of elements and arrangements are described below to simplify this description. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first component on or over a second component may include embodiments where the first and second components are formed in direct contact, and may also include embodiments where additional components may be formed between the first and second components such that the first and second components are not in direct contact. Furthermore, reference numerals and / or letters may be repeated in various examples. Such repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0014] Furthermore, to facilitate the description of one element or component relative to another as shown in the figure, spatially related terms such as "below," "under," "below," "above," and "above" may be used here. In addition to the directions depicted in the figure, spatially relative terms are intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein will be interpreted accordingly.

[0015] According to various embodiments, a cleaning process is performed to remove plasma-generated byproducts from blades of the lithography system. The cleaning process includes preheating the lower portion of the blade to reduce the temperature difference between the lower and upper portions of the blade. Subsequently, the upper and lower portions of the blade are uniformly heated to melt the byproducts, allowing them to drip from the blade and be discharged. Preheating the lower portion of the blade reduces the time required for the upper and lower portions of the blade to reach the temperature necessary to melt the byproducts. Reducing the time required for the upper and lower portions of the blade to reach the required temperature lowers the risk of the molten plasma-generated byproducts re-solidifying and damaging components of the lithography system.

[0016] Figure 1 This is a block diagram of a lithography system 10 according to some embodiments. In some embodiments, the lithography system 10 is an extreme ultraviolet (EUV) lithography system operable to perform lithography by exposing a resist layer of a wafer to EUV light. The lithography system 10 includes an EUV source 12 for generating EUV light, an EUV scanner 14 for patterning EUV light and exposing the wafer to the patterned EUV light, and a controller 16 for controlling the components of the lithography system 10.

[0017] EUV source 12 is operable to generate EUV light 18, for example, light having a wavelength in the range of 1 nm to 100 nm, such as a wavelength of about 13.5 nm. In some embodiments, EUV source 12 utilizes a laser-generated plasma (LPP) mechanism to generate EUV light 18. EUV source 12 includes a laser generator 20, a droplet generator 22, a light collector 24, a droplet trap 26, and a byproduct extractor 28.

[0018] Laser generator 20 is operable to generate a high-intensity laser beam 32. In some embodiments, laser generator 20 is a carbon dioxide (CO2) laser system. However, it should be understood that another type of laser system can be used. In some embodiments, the laser beam 32 is generated with an average laser power in the range of 20 kW to 40 kW and a frequency in the range of 40 kHz to 100 kHz. Laser generator 20 can generate any acceptable laser beam 32.

[0019] Droplet generator 22 is operable to provide droplets of material for generating plasma. During operation, the droplets pass through light collector 24 and are directed toward droplet trap 26. As the droplets pass through light collector 24, a laser beam 32 from laser generator 20 is directed toward the droplets. When the laser beam 32 strikes the droplets, the droplets are vaporized, atomized, and ionized, thereby generating plasma. The plasma emits EUV light 18. The material for the droplets can be selected based on the desired wavelength of the EUV light 18. In some embodiments, the material is tin, and droplet generator 22 can be referred to as a tin droplet generator. Because laser generator 20, droplet generator 22, and droplet trap 26 work together to generate plasma, they can be collectively referred to as plasma generators. The plasma generator generates plasma above light collector 24.

[0020] The light collector 24 is operable to collect EUV light 18 emitted when plasma is generated using a plasma generator (e.g., laser generator 20, droplet generator 22, and droplet trap 26). When the droplets are ionized, the resulting EUV light 18 is uniformly dispersed, such that the EUV light 18 is distributed in all orientations. The light collector 24 converges and focuses the EUV light 18 to form a concentrated beam of EUV light 18 for subsequent photolithography exposure processes.

[0021] Droplet trap 26 is operable to capture unreacted droplets from droplet generator 22 for reprocessing. Reprocessing the droplets may include collecting the droplets and returning the collected material to droplet generator 22 to generate additional droplets. When the droplet material is tin, droplet trap 26 may be referred to as a tin droplet trap.

[0022] Byproduct extractor 28 is operable to capture and remove plasma-generated byproducts from EUV source 12. As will be described in more detail later, byproduct extractor 28 is used to remove byproducts from EUV source 12 while avoiding damage to fragile components of EUV source 12, such as photocollector 24.

[0023] EUV scanner 14 is operable to receive EUV light 18 from EUV source 12, pattern the EUV light 18, and expose the resist layer of the wafer to the pattern of the EUV light 18. The resist layer of the wafer is formed of a photosensitive material sensitive to EUV light 18, and the pattern of EUV light 18 can then be transferred to the wafer by developing the photosensitive material to form a resist pattern and then using the resist pattern as an etching mask to etch components in the wafer. EUV scanner 14 includes illuminator 34, mask stage 36, projection optics 38, and wafer stage 40.

[0024] Illuminator 34 is operable to direct EUV light 18 from an EUV source to mask stage 36, particularly to a mask fixed to mask stage 36. Illuminator 34 may include reflective optics, such as a single mirror or a mirror system with multiple mirrors, or refractive optics, such as a single lens or a lens system with multiple lenses (zone plates). In some embodiments, illuminator 34 is operable to adjust the reflective optics to provide off-axis illumination (OAI) to mask stage 36.

[0025] A mask stage 36 is operable to hold a mask onto which EUV light 18 from an illuminator 34 is incident. In some embodiments, the mask stage 36 includes an electrostatic chuck for holding the mask. The mask held to the mask stage 36 includes a reflective layer. The reflective layer reflects the EUV light 18 and defines a pattern of layers of an integrated circuit (IC). When the EUV light 18 incident on the mask held to the mask stage 36, the EUV light 18 is reflected by the reflective layer, and the reflected EUV light 18 has the pattern of the mask.

[0026] The projection optics 38 are operable to collect patterned EUV light 18 from a mask fixed to the mask stage 36 and project the patterned EUV light 18 onto the wafer stage 40, particularly onto a wafer fixed to the wafer stage 40. The projection optics 38 can amplify the patterned EUV light 18. In some embodiments, the projection optics 38 amplifies the patterned EUV light 18 by a magnification of less than 1, thereby reducing the size of the patterned EUV light 18. The projection optics 38 may include refractive or reflective optics.

[0027] The wafer stage 40 is operable to hold a wafer onto which patterned EUV light 18 from the projection optics 38 is irradiated. In some embodiments, the wafer stage 40 includes an electrostatic chuck for holding the wafer. For example, the wafer may be a semiconductor wafer, such as a silicon wafer, or another type of wafer to be patterned.

[0028] Controller 16 is connected to and operable to control components of lithography system 10. Specifically, controller 16 is operable to control lithography system 10 to perform lithography processes and cleaning processes. Controller 16 can be used to store and control parameters related to the operation of EUV source 12 and EUV scanner 14. Controller 16 can be implemented in hardware or software, and parameters can be hard-coded or input to controller 16 via input instruments. For example, controller 16 may include a processor and a non-transitory computer-readable storage medium storing a program implemented by the processor, wherein the program includes instructions for controlling components of EUV source 12. Similarly, controller 16 may include circuitry such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA) for controlling components of EUV source 12. As will be described in more detail later, the cleaning process performed by controller 16 includes controlling byproduct extractor 28 to capture and remove plasma-generated byproducts from EUV source 12 while avoiding damage to fragile components of EUV source 12.

[0029] Figures 2A-2B This is a detailed view of EUV source 12 according to some embodiments. Figure 2A This is a schematic diagram of the EUV source 12 in operation. Figure 2B This is a 3D sectional view of EUV source 12. For clarity, some components have been omitted from the figure.

[0030] EUV source 12 also includes a window 42 for receiving laser beam 32. Window 42 extends through the bottom of light collector 24. Laser beam 32 is guided from laser generator 20 through window 42 (see...). Figure 1 The laser beam 32 is guided from the laser generator 20 to the window 42 via a beam transmission system, which is, for example, one or more mirrors operable to transmit the laser beam 32 by reflecting it in a desired orientation. The window 42 comprises a suitable material that is substantially transparent to the laser beam 32.

[0031] The light collector 24 is designed with a coating material and a shape that serves as a mirror for generating EUV light 18. In some embodiments, the light collector 24 has an elliptical shape. In some embodiments, the outer diameter of the light collector 24 is in the range of 400 mm to 600 mm, and the window 42 has a diameter in the range of 30 mm to 150 mm. Other shapes and / or sizes may be used for the light collector 24 and the window 42. In some embodiments, the coating material of the light collector 24 comprises multiple reflective layers, such as multiple molybdenum-silicon film pairs (e.g., a molybdenum layer above or below a silicon layer in each thin pair). The light collector 24 may also include a cover layer (e.g., a ruthenium layer) coated on the multiple reflective layers to sufficiently reflect the EUV light 18. In some embodiments, the light collector 24 may also include any grating structure designed to effectively scatter laser beams 32 that can reach the surface of the light collector 24. For example, a silicon nitride layer may be coated on the light collector 24 and may be patterned to have a grating pattern.

[0032] EUV source 12 also includes a lower cone 46 and an intermediate focus (IF) module 48. The lower cone 46 may include a processing surface that further guides EUV light 18 to the IF module 48. The IF module 48 is operable to provide an intermediate focus for the EUV light 18 to deliver it to the EUV scanner 14 (see [link to documentation]). Figure 1 The IF module 48 may include, for example, an IF-capquick-connect module for supplying EUV light 18 to the scanner.

[0033] As described above, EUV light 18 is generated when the laser beam 32 strikes the droplet 44 from the droplet generator 22. The laser beam 32 from the laser generator 20 is generated in pulses and is synchronized to enter the path of the laser beam 32 and strike the droplet 44 through the window 42 while receiving peak power from the laser generator 20. When the laser beam 32 strikes the droplet 44, the droplet 44 is vaporized, atomized, and ionized to generate plasma, thereby generating EUV radiation and droplet byproducts. Droplet byproducts are generated due to the vaporization or atomization of the droplet 44. These byproducts are dispersed during their formation, so if their formation is not mitigated, they will be distributed on the components of the EUV source 12 (e.g., the window 42 and the lower cone 46). As described above, the droplet 44 can be a tin droplet. Tin contaminants on the window 42 and the lower cone 46 will reduce the efficiency of the EUV source 12. Byproduct extractor 28 (see Figure 1 It is operable to capture droplet byproducts as they are generated, so that they do not distribute on the components of EUV source 12, thereby improving the efficiency of EUV source 12. Byproduct extractor 28 includes blade structure 62, heater 64, cooler 66, byproduct transport ring 68, heat shield 70, discharge pipe 74 and collector 76.

[0034] The blade structure 62 includes a blade 80 and a slot 82. The blade 80 projects from the sidewall of the blade structure 62 and extends along the sidewall of the blade structure 62 in a direction parallel to the orientation of the EUV light 18. As will be discussed later... Figure 3C Described, the blade 80 may be V-shaped. A groove 82 is disposed below the blade 80. The blade structure 62 may be a machined structure formed of metal. During operation, the blade 80 captures generated droplet byproducts. A cleaning process can be performed between photolithography processes to clean the byproducts distributed on the blade 80. As will be described in more detail later, the blade 80 is heated during the cleaning process to melt and recover the material, such as tin, that has accumulated on the blade 80 during the photolithography process. When heated, the byproducts flow down the blade 80 and drip into the groove 82. The light collector 24 is an expensive, precision instrument that is being replaced, so contamination of the light collector 24 is undesirable. According to various embodiments, the byproduct extractor 28 performs a cleaning process to remove droplet byproducts from the blade 80 in a manner that increases the chance of droplet byproducts dripping into the groove 82 rather than onto the light collector 24. Therefore, damage to the lamp collector 24 during the cleaning process can be avoided, thereby increasing the lifetime of the EUV source 12.

[0035] Heater 64 is disposed around blade 80. Heater 64 may include a plurality of heating elements periodically disposed around blade structure 62, or a single heating element extending continuously around blade. In some embodiments, heater 64 includes heating rods, such as resistance heating elements.

[0036] Cooler 66 is disposed around heater 64. Cooler 66 may include a plurality of cooling elements periodically disposed around blade structure 62, or a single cooling element extending continuously around the blade. In some embodiments, cooler 66 includes cooling elements such as water-cooled pipes, thermoelectric coolers, etc.

[0037] A byproduct transport ring 68 is disposed below the blade structure 62, particularly below the drain trough 82. Therefore, the byproduct transport ring 68 is positioned above the light collector 24. In some embodiments, the byproduct transport ring 68 has an annular shape, such that it extends around the bottom footprint of the blade structure 62 while still allowing EUV light 18 to pass through. As will be described in more detail later, the byproduct transport ring 68 is operable to collect byproducts that drip into the trough 82 during the cleaning process of the blade 80, thereby allowing the byproducts to be transported to the collector 76. To prevent the byproducts from solidifying during transport, the byproduct transport ring 68 includes a heater 78 (not shown separately) operable to heat the byproduct transport ring 68 during operation, such that the byproducts remain in a liquid phase. For example, the heater 78 may be a resistance heating element that extends around and through the core of the byproduct transport ring 68.

[0038] A heat shield 70 is disposed below the byproduct transport ring 68. The heat shield 70 is formed of a heat-resistant material and is operable to protect underlying components (e.g., light collector 24) when the byproduct transport ring 68 is heated. In some embodiments, the heat shield 70 includes channels for holding and supporting the byproduct transport ring 68. The channels in the heat shield 70 have the same shape as the byproduct transport ring 68 (e.g., annular). Openings 72 in the byproduct transport ring 68 and the heat shield 70 allow byproducts in the byproduct transport ring 68 to drip into the discharge pipe 74 and flow through the collector 76.

[0039] The discharge pipe 74 is operable to transport by-products from the by-product transport ring 68 to the collector 76. The collector 76 is operable to store the by-products. The discharge pipe 74 and the collector 76 may be formed of a material that is substantially chemically inert to the by-products, such as polyvinyl chloride (PVC). The discharge pipe 74 connects the heat shield 70 to the collector 76 and may extend through the opening 72.

[0040] Some or all of the components of the EUV source 12 are disposed within the process chamber 50. In some embodiments, the process chamber 50 is maintained under vacuum during processing. Air absorbs certain types of light, therefore maintaining the process chamber 50 under vacuum can improve process efficiency.

[0041] According to various embodiments, a cleaning process for the blade 80 is performed between photolithography processes to remove byproducts from the blade 80. The cleaning process includes a heating cycle and a cooling cycle. During the heating cycle, the blade 80 is heated using a heater 64 and a byproduct transport ring 68, causing the byproducts collected on the blade 80 to melt and flow down the blade 80. The molten byproducts drip into a drip tray 82, onto the byproduct transport ring 68, and then into a discharge pipe 74 (see...). Figure 2A ), causing them to eventually flow to collector 76 (see Figure 2A During the cooling cycle, the blades 80 are cooled using cooler 66, allowing them to operate safely again.

[0042] Figures 3A-3C This is a partial view of the blade structure 62 according to some embodiments. Figure 3A This is a schematic top view of part of the blade structure 62. Figure 3B This is a schematic side view of part of the blade structure 62. Figure 3C This is a three-dimensional view of part of the blade structure 62. For clarity, some parts have been omitted from the view.

[0043] The blade structure 62 also includes an attachment structure 84 for each blade 80. The attachment structure 84 attaches the blade 80 to a sidewall of the blade structure 62 (e.g., to the main structure of the blade structure 62). The attachment structure 84 may include, for example, a hinge physically coupled to the blade 80 and the sidewall of the blade structure 62, such that the blade 80 is operable to oscillate about the hinge. In some embodiments, the attachment structure 84 also includes a motor for actuating the blade 80 to move it during operation.

[0044] In the illustrated embodiment, heater 64 includes a plurality of heating elements and cooler 66 includes a plurality of cooling elements. Specifically, heater 64 and cooler 66 are provided in each blade structure 62, such that each blade 80 can be individually heated and cooled. For example, heater 64 for blade 80 may extend along the length of blade 80, and cooler 66 for blade 80 may extend along the length of attachment structure 84. During operation (e.g., a cleaning process), heat is transferred from heater 64 to blade 80 during the heating cycle of the cleaning process, and heat is transferred from blade 80 to cooler 66 during the cooling cycle of the cleaning process. In embodiments where cooler 66 is a cooling pipe arranged in attachment structure 84, heat can be transferred from blade 80 to cooler 66 by flowing water through the cooling pipe, such that heat is carried away from attachment structure 84 and blade 80 by conduction. Figure 3C As shown, the blade 80 may be V-shaped (e.g., the sidewalls of the blade 80 form a V), and a heater 64 for the blade 80 is disposed in the hollow region formed by the sidewalls of the blade 80. In such an embodiment, heat is transferred from the heater 64 to the blade 80 by radiation or convection.

[0045] As described above, a cleaning process is performed to remove byproducts from the blade 80. Heater 64 is used to heat the blade 80 during the cleaning process and provides substantially uniform heating. However, heat is generated during the photolithography process, and most of the generated heat is applied to the top and lower cone 46 of the blade structure 62 (see [link to photolithography]). Figure 2BTherefore, during the photolithography process and at the start of the cleaning process, the upper part 80U of blade 80 is hotter than the lower part 80L of blade 80. As a result, if only heater 64 is used to heat blade 80, the upper part 80U of blade 80 will reach the required temperature before the lower part 80L of blade 80. The temperature of the upper part 80U of blade 80 (also referred to as the upper temperature of blade 80) will therefore be higher than the melting point of the byproduct, while the temperature of the lower part 80L of blade 80 (also referred to as the lower temperature of blade 80) will still be lower than the solidification point of the byproduct. According to various embodiments, the byproduct transport ring 68 is also heated during the heating cycle of the cleaning process and is heated before heater 64 is turned on. Because the byproduct transport ring 68 is located below blade 80, heating the byproduct transport ring 68 heats the lower part 80L of blade 80. Specifically, heat is transferred from the byproduct transport ring 68 to blade 80 by radiation, conduction, or convection. Before heating the blade 80 using heater 64, the amount of heating performed using byproduct transport ring 68 is controlled to reduce the temperature difference between the upper 80U and lower 80L of the blade 80. Both the byproduct transport ring 68 and heater 64 can then be used to heat the blade 80, allowing for more uniform heating and thus reducing the time it takes for the upper 80U and lower 80L of the blade 80 to reach the desired temperature (e.g., the melting point of the byproduct). More uniform heating of the blade 80 advantageously reduces the amount of time it takes for molten byproducts to flow downwards along the upper 80U of the blade 80 and re-solidify upon reaching the lower 80L. Re-solidification of byproducts in the lower 80L of the blade 80 will lead to the coalescence and accumulation of byproducts, eventually causing the accumulated byproducts to separate from the lower 80L of the blade 80, potentially falling onto and damaging the light collector 24 (see [link to product description]). Figures 2A-2B Heating the blades 80 more evenly during the cleaning process can reduce the risk of damage to the light collector 24 and increase the lifespan of the EUV source 12.

[0046] Figure 4 This is a flowchart of a method 400 for operating a lithography system 10 according to some embodiments. Method 400 may be provided by, for example, a controller 16 (see...). Figure 1 The controller 16 can execute method 400 by controlling the components of the lithography system 10, therefore, when describing method 400, reference is made to the method for... Figures 1-3C The component described.

[0047] In step 402, one or more photolithography processes are performed to process one or more semiconductor wafers. The photolithography process is performed by securing the wafer to a wafer stage 40 and by securing a mask for the wafer to a mask stage 36. EUV light 18 is then generated using an EUV source 12 and scanned on the wafer using an EUV scanner 14. The wafer is coated with an EUV light-sensitive resist layer 18. The resist layer can be formed of a positive or negative resist. The resist layer can be a photoresist, which can be formed on a target substrate by spin coating, soft baking, or a combination thereof. The wafer processing can be repeated multiple times as needed. During the photolithography process, the temperature of the blade 80 is below a predetermined value. This predetermined value is less than or equal to the melting point of plasma-generated byproducts, such that any byproducts accumulating on the blade 80 during the photolithography process remain solid and do not melt. For example, when the droplet 44 is tin, the temperature of the blade 80 is below the melting point of tin. In some embodiments, the predetermined value is 140°C.

[0048] In step 404, a cleaning process is performed to remove byproducts from EUV source 12. The cleaning process includes heating the blade 80 of blade structure 62 until the byproducts on the blade 80 melt, and then transferring the melted byproducts from blade structure 62 (e.g., from process chamber 50). Heating the blade 80 includes preheating the lower portion 80L of the blade 80 using a byproduct transfer ring 68, followed by heating both the upper portion 80U and the lower portion 80L of the blade 80 together using a heater 64. During preheating, the upper portion 80U of the blade 80 is not heated (or is heated less than the lower portion 80L of the blade 80). During the cleaning process, the temperature of the blade 80 is higher than the predetermined value described in step 402. The blade 80 is then cooled, and the heating / cooling cycle is repeated the required number of times. Each of these steps will be described in more detail. After the cleaning process, the photolithography process can be performed again.

[0049] In step 406, the by-product transport ring 68 is heated. The by-product transport ring 68 can be heated by activating a heater (not shown separately) inside it. For example, when the by-product transport ring 68 includes a heater 78 (e.g., a resistance heating element), it can be heated by supplying current to the resistance heating element. The by-product transport ring 68 is heated for a predetermined duration until a predetermined temperature is reached. In some embodiments, the by-product transport ring 68 is heated for a duration ranging from 3 to 4 hours until it reaches a temperature ranging from 100°C to 500°C. Heating the by-product transport ring 68 to temperatures below 100°C may result in the formation of molten metal. Other acceptable durations or temperatures can be used when heating the by-product transport ring 68. As described above, heat is transferred from the by-product transport ring 68 to the lower portion 80L of the blade 80. Therefore, heating the by-product transport ring 68 heats the lower portion 80L of the blade 80. Therefore, heating the by-product conveying ring 68 reduces the temperature difference between the upper part 80U and the lower part 80L of the blade 80. Both the by-product conveying ring 68 and the lower part 80L of the blade 80 are heated. The blade 80 is heated to a temperature below the melting point of the by-products on the blade 80 during preheating, so that the by-products do not melt when the temperature difference between the upper part 80U and the lower part 80L of the blade 80 is reduced.

[0050] In some embodiments, the byproduct transport ring 68 is heated at a single, continuous heating rate. For example, the heater 78 of the byproduct transport ring 68 can be maintained at a fixed temperature, which allows the byproduct transport ring 68 to be heated at a continuous heating rate. When the heater 78 is a resistance heating element, it can be maintained at a fixed temperature by providing a constant current to the resistance heating element. In some embodiments, the heater 78 of the byproduct transport ring 68 is maintained at a temperature in the range of 100°C to 600°C, thereby allowing the byproduct transport ring 68 to be heated at a rate in the range of 60°C / hour to 500°C / hour.

[0051] In some embodiments, the byproduct transport ring 68 is heated at multiple heating rates with increasing values. For example, the heater 78 of the byproduct transport ring 68 may be heated with an increasing heating gradient. When the heater 78 is a resistance heating element, it can be heated with a heating gradient by providing an increasing current to the resistance heating element. In some embodiments, the heater 78 of the byproduct transport ring 68 gradually increases from an initial temperature in the range of 100°C to 200°C to a final temperature in the range of 200°C to 500°C.

[0052] In step 408, the blades 80 are heated. The blades 80 can be heated by turning on the heater 64 and turning off the cooler 66 (if they are in the on state). For example, when the heater 64 is a resistance heating element, it can be heated by supplying current to the resistance heating element. The blades 80 are heated for a predetermined duration until they reach a predetermined temperature. In some embodiments, the blades 80 are heated for a duration ranging from 1 to 2 hours until the upper portion 80U of the blade 80 is at a temperature ranging from 200°C to 350°C and until the lower portion 80L of the blade 80 is at a temperature ranging from 150°C to 350°C. Heating the blades 80 to temperatures below 100°C may result in the formation of tin wool. Other acceptable durations or temperatures can be used when heating the blades 80. The lower portion 80L of the blade 80 can be heated to a lower temperature than the upper portion 80U of the blade 80. Both the upper portion 80U and the lower portion 80L of the blade 80 are heated to temperatures above the melting point of byproducts on the blades 80.

[0053] Heating of the blade 80 does not begin until the byproduct transport ring 68 has been heated for the desired duration. Specifically, a wait is performed between the heating of the byproduct transport ring 68 and the heating of the blade 80, such that the byproduct transport ring 68 is heated for a predetermined duration before heating of the blade 80 begins. In some embodiments, the byproduct transport ring 68 is heated for a duration ranging from 0.5 hours to 1.0 hour before heating of the blade 80 begins. Other acceptable wait times may be used. As a result, the byproduct transport ring 68 is preheated for a first duration, and then the blade 80 and the byproduct transport ring 68 are heated together for a second duration. Therefore, the temperature difference between the upper portion 80U and the lower portion 80L of the blade 80 is reduced before the blade 80 is heated by the heater 64.

[0054] In step 410, blades 80 are cooled. Blades 80 can be cooled by turning off heater 64 and turning on cooler 66. For example, when cooler 66 is a water-cooled pipe, cooler 66 can be cooled by water flowing through the cooling pipe. Blades 80 are cooled for a predetermined duration until they reach a predetermined temperature. In some embodiments, blades 80 are cooled for a duration ranging from 0.2 hours to 0.5 hours until the upper portion 80U of blade 80 is at a temperature ranging from 100°C to 300°C and until the lower portion 80L of lower blade 80 is at a temperature ranging from 100°C to 200°C. Cooling blades 80 to temperatures below 100°C may result in the formation of tin wool. Other acceptable durations or temperatures may be used when cooling blades 80. Both the upper portion 80U and the lower portion 80L of blade 80 are cooled to temperatures below the melting point of the plasma generation byproducts that subsequently form.

[0055] In step 412, the byproduct transport ring 68 is cooled. The byproduct transport ring 68 can be cooled by shutting off the heater (not shown separately) inside it. Thus, only the lower portion 80L of the blade 80 is cooled, while the upper portion 80U of the blade 80 is not cooled. The byproduct transport ring 68 is cooled for a predetermined duration until it reaches a predetermined temperature. In some embodiments, the byproduct transport ring 68 is cooled for a duration ranging from 0.1 hours to 0.3 hours until it reaches a temperature ranging from 100°C to 300°C. Cooling the byproduct transport ring 68 to temperatures below 100°C may result in the formation of tin wool. Other acceptable durations or temperatures may be used when cooling the byproduct transport ring 68. The byproduct transport ring 68 is cooled to a temperature below the melting point of the subsequently formed plasma-generated byproducts.

[0056] Cooling of the byproduct transport ring 68 does not begin until the blades 80 have been cooled for a desired duration. Specifically, a wait is performed between the cooling of the blades 80 and the cooling of the byproduct transport ring 68, such that the blades 80 are cooled for a predetermined duration before the cooling of the byproduct transport ring 68 begins. In some embodiments, the blades 80 are cooled for a duration ranging from 0.5 hours to 1.0 hour before the cooling of the byproduct transport ring 68 begins. Other acceptable wait times may be used. As a result, the blades 80 are pre-cooled for a first desired duration, and then the byproduct transport ring 68 is cooled for a second desired duration.

[0057] After the blades 80 have cooled, the heating and cooling cycles can be repeated as many times as desired. Each heating and cooling cycle is called a thermal cycle. In some embodiments, approximately 5 / 6 of the thermal cycles are used to perform cooling and approximately 1 / 6 of the thermal cycles are used to perform heating. Any desired amount of heating and cooling can be performed for each thermal cycle. Using shorter thermal cycles may be more expensive, but it reduces the risk of damage to the light collector 24.

[0058] Figure 5 This is a temperature graph of components of a lithography system during a cleaning process, according to some embodiments. The component temperatures are plotted over time. As shown, the temperatures of the upper portion 80U and the lower portion 80L of blade 80 are respectively at time t. 1U and t 1L Exceeding the melting point T of the byproduct M As a result of the transport of preheating byproducts in loop 68, time t 1U and t 1L The time difference Δt1 between them decreases. In some embodiments, the time difference Δt1 is in the range of 5 to 30 minutes. Reducing the time difference Δt1 reduces the risk of damaging the light collector 24 during the cleaning process. As further shown, the temperatures of the upper part 80U and the lower part 80L of the blade 80 are respectively at time t 2U and t2L The temperature dropped below the melting point T of the byproduct. M As a result of pre-cooling the blades 80, time t 2U and t 2L The time difference Δt2 decreases. In some embodiments, the time difference Δt2 is in the range of 15 to 60 minutes. Reducing the time difference Δt2 lowers the risk of damaging the light collector 24 during the cleaning process. Figure 6 The illustration shows experimental data for a photolithography system according to some embodiments. It can be seen that the risk of damage to the light collector 24 decreases as the sum of Δt1 and Δt2 decreases.

[0059] The embodiments offer advantages. Preheating the byproduct transport ring 68 during the heating cycle of the cleaning process reduces the temperature difference between the upper 80U and lower 80L of the blade 80. This reduces the time it takes for the upper 80U and lower 80L of the blade 80 to reach the desired temperature (e.g., the melting point of the plasma-generated byproducts) when the blade 80 is subsequently heated during the heating cycle of the cleaning process. Reducing the time for the upper 80U and lower 80L of the blade 80 to reach the desired temperature lowers the risk of plasma-generated byproducts re-solidifying and falling onto the photocollector 24 during the cleaning process. This can therefore increase the lifetime of the EUV source 12. In experiments, the availability of the lithography system increased from 20% to 40%, the maintenance time of the lithography system was reduced to the range of 24 to 48 hours, and the lifetime of the photocollector 24 increased to 20 to 45 days.

[0060] The aforementioned advanced photolithography processes, methods, and materials can be used in many applications, including fin field-effect transistors (FinFETs). For example, fins can be patterned to create relatively tight spacing between components, as disclosed above. Furthermore, the spacers used to form the fins of the FinFET, also known as mandrels, can be processed according to the aforementioned disclosure.

[0061] In one embodiment, a method includes: heating a byproduct transport ring of an extreme ultraviolet (EUV) source, the byproduct transport ring being disposed below a blade of the EUV source; heating the blade after heating the byproduct transport ring for a first duration; cooling the blade after heating the blade; and cooling the byproduct transport ring after cooling the blade for a second duration. In some embodiments of the method, heating the byproduct transport ring reduces the temperature difference between the upper and lower portions of the blade. In some embodiments of the method, heating the byproduct transport ring includes heating the byproduct transport ring at a single, continuous heating rate. In some embodiments of the method, heating the byproduct transport ring includes heating the byproduct transport ring at multiple, incrementally increasing heating rates. In some embodiments, the method further includes: generating plasma with the EUV source, the byproducts of the plasma being distributed on the blade during plasma generation, wherein the byproduct transport ring is heated to a first temperature below the melting point of the byproducts, and the blade is heated to a second temperature above the melting point of the byproducts. In some embodiments of the method, generating plasma includes: generating droplets of material; and impacting the droplets with a laser beam, the droplets being vaporized, atomized, and ionized to generate plasma. In some embodiments of the method, the material is tin. In some embodiments of the method, the first duration is in the range of 0.5 hours to 1.0 hours and the second duration is in the range of 0.5 hours to 1.0 hours.

[0062] In one embodiment, a method includes: generating plasma in a process chamber by impinging a tin droplet with a laser beam, the tin droplet byproducts distributed on blades in the process chamber, wherein during plasma generation, the upper part of the blade has a higher temperature than the lower part of the blade; reducing the temperature difference between the upper and lower parts by heating the lower part of the blade; melting the tin droplet byproducts on the blade by heating the upper and lower parts of the blade after reducing the temperature difference; and extracting the molten tin droplet byproducts from the process chamber. In some embodiments of the method, heating the lower part of the blade includes: heating a byproduct transport ring disposed below the blade. In some embodiments of the method, heating the byproduct transport ring includes: providing a constant current to a heating element of the byproduct transport ring. In some embodiments of the method, heating the byproduct transport ring includes: providing an increased current to a heating element of the byproduct transport ring. In some embodiments of the method, the tin droplet byproducts do not melt during the reduction of the temperature difference between the upper and lower parts. In some embodiments of the method, heating the upper and lower parts of the blade includes: activating a heating element that extends along the length of the blade. In some embodiments, the method further includes: after removing the byproduct of the tin droplet from the process chamber, cooling the upper and lower portions of the blade; and after cooling the upper and lower portions of the blade, cooling the lower portion of the blade without cooling the upper portion of the blade.

[0063] In one embodiment, an instrument includes: a plasma generator; a light collector; a byproduct transport ring above the light collector, the byproduct transport ring including a first heating element; blades above the byproduct transport ring; a second heating element extending along the length of the blades; and a controller configured to: generate plasma above the light collector using the plasma generator, the plasma generating byproducts distributed on the blades; heat the first heating element of the byproduct transport ring to reduce the temperature difference between the upper and lower parts of the blades; and, after reducing the temperature difference, heat the second heating element to melt the plasma-generated byproducts distributed on the blades. In some embodiments, the instrument further includes: a discharge pipe extending through an opening in the byproduct transport ring; and a collector connected to the discharge pipe, through which the plasma-generated byproducts are discharged to the collector upon melting. In some embodiments, the instrument further includes: a heat shield having a channel for holding the byproduct transport ring, the discharge pipe extending through an opening in the heat shield. In some embodiments of the instrument, the plasma generator includes: a droplet generator configured to provide droplets of material; a laser generator configured to generate a laser beam that ionizes the droplets of material to generate plasma; and a droplet trap configured to trap unreacted droplets of material from the droplet generator. In some embodiments, the instrument further includes: a cooling element, wherein the controller is further configured to: flow water through the cooling element to cool the blades after melting plasma generation byproducts distributed on the blades; and cool the byproduct transport ring after cooling the blades.

[0064] The foregoing has outlined features of several embodiments to enable those skilled in the art to better understand various aspects of this disclosure. Those skilled in the art will understand that they can readily use this disclosure as a basis for designing or modifying other processes and structures for performing the same purposes and / or achieving the same advantages of the embodiments described herein. Those skilled in the art should also recognize that such equivalent structures do not depart from the spirit and scope of the invention, and that various alterations, substitutions, and modifications can be made to this document without departing from the spirit and scope of the invention.

Claims

1. A photolithography method, comprising: Plasma is generated using an extreme ultraviolet source, and the byproducts of the plasma are distributed on the blades during the generation of the plasma. Heating the byproduct transport ring of the extreme ultraviolet source, the byproduct transport ring being disposed below the blade of the extreme ultraviolet source; After heating the byproduct transport ring for a first duration, the blade is heated, wherein the byproduct transport ring is heated to a first temperature, the first temperature being below the melting point of the byproduct, and wherein the blade is heated to a second temperature, the second temperature being above the melting point of the byproduct; After heating the blade, the blade is cooled; and After the second duration of cooling of the blades, the byproduct transport ring is cooled.

2. The photolithography method according to claim 1, wherein, Heating the byproduct transport ring reduces the temperature difference between the upper and lower parts of the blade.

3. The photolithography method according to claim 1, wherein, Heating the byproduct transport ring includes heating the byproduct transport ring at a single, continuous heating rate.

4. The photolithography method according to claim 1, wherein, Heating the byproduct transport ring includes heating the byproduct transport ring at multiple heating rates with increasing values.

5. The photolithography method according to claim 1, wherein, The byproduct transport ring is cooled to a temperature in the range of 100°C to 300°C.

6. The photolithography method according to claim 5, wherein generating the plasma comprises: The material is generated as droplets; as well as The droplets are bombarded with a laser beam, which vaporizes, atomizes, and ionizes them to generate the plasma.

7. The photolithography method according to claim 6, wherein, The material is tin.

8. The photolithography method according to claim 1, wherein, The first duration is in the range of 0.5 hours to 1.0 hours, and the second duration is in the range of 0.5 hours to 1.0 hours.

9. A photolithography method, comprising: Plasma is generated in a process chamber by bombarding tin droplets with a laser beam. The byproducts of the tin droplets are distributed on blades in the process chamber. During the generation of the plasma, the upper part of the blades has a higher temperature than the lower part of the blades. The temperature difference between the upper part and the lower part is reduced by heating the lower part of the blade; After reducing the temperature difference between the upper part and the lower part, the byproducts of the tin droplets on the blade are melted by heating the upper part and the lower part of the blade; as well as The byproducts of the molten tin droplets are extracted from the process chamber.

10. The photolithography method according to claim 9, wherein, Heating the lower part of the blade includes: Heating is applied to the byproduct transport ring located below the blades.

11. The photolithography method according to claim 10, wherein, Heating the byproduct transport ring includes: A constant current is supplied to the heating element of the byproduct transport ring.

12. The photolithography method according to claim 10, wherein, Heating the byproduct transport ring includes: An increased current is supplied to the heating element of the byproduct transport ring.

13. The photolithography method according to claim 9, wherein, The byproducts of the tin droplet do not melt during the reduction of the difference between the upper and lower temperatures.

14. The photolithography method according to claim 9, wherein heating the upper portion and the lower portion of the blade comprises: The heating element is turned on, and the heating element extends along the length of the blade.

15. The photolithography method according to claim 9, further comprising: After the byproduct of the tin droplet is extracted from the process chamber, the upper part and the lower part of the blade are cooled. as well as After cooling the upper part and the lower part of the blade, the lower part of the blade is cooled but the upper part of the blade is not cooled.

16. A photolithography instrument, comprising: Plasma generator; Light collector; A byproduct transport ring is located above the light collector, and the byproduct transport ring includes a first heating element; The blade is located above the byproduct transport ring; A second heating element extends along the length of the blade; The controller is configured to: generate plasma above the light collector using the plasma generator, the plasma generating byproducts distributed on the blade; heat the first heating element of the byproduct transport ring to reduce the temperature difference between the upper and lower parts of the blade; and after reducing the temperature difference, heat the second heating element to melt the plasma-generated byproducts distributed on the blade.

17. The photolithography instrument according to claim 16, further comprising: The discharge pipe extends through an opening in the byproduct transport ring; and A collector, connected to the discharge pipe, through which plasma-generated byproducts are discharged as they melt into the collector.

18. The photolithography instrument according to claim 17, further comprising: A heat shield having a channel for maintaining the byproduct transport ring, the discharge pipe extending through an opening in the heat shield.

19. The photolithography instrument according to claim 16, wherein, The plasma generator includes: A droplet generator configured to provide droplets of material; A laser generator configured to generate a laser beam that ionizes the droplets of the material to generate the plasma; and A droplet trap configured to capture unreacted droplets of the material from the droplet generator.

20. The photolithography instrument according to claim 16, further comprising: Cooling elements, The controller is further configured to: melt the plasma-generated byproducts distributed on the blades, then allow water to flow through the cooling element to cool the blades; and after cooling the blades, cool the byproduct transport ring.

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