Method and EUV lithography system for extreme ultraviolet (EUV) lithography systems

Abstract

Methods for an extreme ultraviolet (EUV) lithography system including a radiation source having a laser device configured with a mechanism to generate EUV radiation are provided. The methods include collecting a laser beam profile of a laser beam from the laser device in a 3-dimensional (3D) mode, collecting an EUV energy distribution of the EUV radiation generated by the laser beam in a 3D mode, performing an analysis of the laser beam profile and the EUV energy distribution to obtain analysis data, and adjusting the radiation source to enhance the EUV radiation based on the analysis data. Embodiments of the invention also provide an extreme ultraviolet (EUV) lithography system.

Description

TECHNICAL FIELD

[0001] Embodiments of the present invention relate to methods for and extreme ultraviolet lithography systems. BACKGROUND

[0002] The semiconductor integrated circuit (IC) industry has experienced rapid growth. ICs have been used to improve the performance of electronic equipment in almost every technical field. Improvements in IC materials and design have produced ICs with greater functionality, higher speed, and lower costs. Defining and manufacturing ICs with a smaller feature size enables an increase in functionality and an increase in the number of terminals. The IC industry's goals are constantly driving up levels of integration and shrinking the size of features on ICs. In the course of IC development, typically the number of electrical devices per chip area has increased, and the size of individual devices has decreased. As a result, the pattern design rules have become more stringent and designs of devices have become more complex. In order to keep up with this progress, the photolithography process used to produce the devices must also advance. For example, there is an increasing need to implement higher resolution photolithography processes. One photolithography technique is extreme ultraviolet lithography (EUVL). EUVL employs a scanner that uses light in the extreme ultraviolet (EUV) region having a wavelength of about 1 nm to 100 nm. The EUV scanner uses reflective rather than refractive optics, i.e., mirrors rather than lenses. However, while existing photolithography techniques are generally adequate for their intended purpose, they are not entirely satisfactory in all respects. SUMMARY

[0003] Some embodiments of the present invention provide a method for an extreme ultraviolet (EUV) lithography system, the EUV lithography system including a radiation source having a laser device configured with a mechanism for generating extreme ultraviolet radiation, the method comprising: collecting a laser beam profile of a laser beam from the laser device in a 3-dimensional (3D) mode; collecting an extreme ultraviolet energy distribution of the extreme ultraviolet radiation generated by the laser beam in the 3D mode; performing an analysis on the laser beam profile and the extreme ultraviolet energy distribution to obtain analysis data; and adjusting the radiation source according to the analysis data to enhance the extreme ultraviolet radiation.

[0004] Another embodiment of the present invention provides an extreme ultraviolet (EUV) lithography system, comprising: a radiation source for generating EUV radiation, wherein the radiation source comprises a laser source, a target material droplet generator, and an EUV collector configured in a vessel; a mask table configured to hold an EUV mask; a wafer table configured to hold a semiconductor wafer; an optical module designed to direct the EUV radiation from the radiation source in a lithography exposure process to image an IC pattern defined on the EUV mask to the semiconductor wafer; and an EUV control system integrated with the radiation source, wherein the EUV control system comprises a 3-dimensional diagnostic module (3DDM) designed to collect data of the radiation source in a 3-dimensional mode, an analysis module designed to analyze the collected data, and an EUV control module designed to adjust the radiation source, wherein the 3DDM is embedded in the radiation source, wherein the analysis module is connected with the 3DDM and the EUV control module, and wherein the EUV control module is connected with the analysis module and the radiation source.

[0005] Yet another embodiment of the present invention provides a method for an extreme ultraviolet (EUV) lithography system, the EUV lithography system comprising a radiation source having a laser device and a laser-produced plasma mechanism for generating EUV radiation, the method comprising: collecting 3-dimensional (3D) data of the radiation source, the 3D data comprising a laser beam profile and an EUV energy of the EUV radiation; performing analysis on the laser beam profile and the EUV energy to obtain correlation data; and adjusting the radiation source according to the correlation data to enhance the EUV radiation. BRIEF DESCRIPTION OF DRAWINGS

[0006] Various aspects of the present invention can be best understood with reference to the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with the standard practice in the industry, various components are not drawn to scale. In fact, the dimensions of the various components can be arbitrarily increased or decreased for the sake of discussion clarity.

[0007] Figure 1 is a block diagram of an EUV lithography system having an EUV control system constructed in accordance with some embodiments;

[0008] Figure 2 is a schematic diagram of an EUV lithography system constructed in accordance with some embodiments having a 3D monitor embedded;

[0009] Figure 3 is a schematic diagram of an EUV lithography system constructed in accordance with some embodiments having a 3D monitor embedded; Figure 1 is a schematic diagram of an EUV radiation source in the EUV lithography system of

[0010] Figure 4 is a schematic diagram of an EUV radiation source in the EUV lithography system of Figure 1 is a schematic diagram of an EUV radiation source in the EUV lithography system of

[0011] Figure 5It is constructed according to some embodiments. Figure 1 A schematic diagram of a target material droplet used to generate plasma and generate EUV radiation energy from the plasma in an EUV lithography system;

[0012] Figure 6 A laser-generated plasma (LPP) process constructed according to some embodiments is shown;

[0013] Figure 7 This is a block diagram of an EUV control system constructed according to some embodiments;

[0014] Figure 8 This is a schematic diagram of a correlation analysis performed by a correlation analysis unit of an EUV control system, constructed according to some embodiments.

[0015] Figure 9 This is a schematic diagram of machine matching analysis performed by the tool matching unit of an EUV control system, constructed according to some embodiments;

[0016] Figure 10 This is a schematic diagram of a modeling process implemented by a modeling unit of an EUV control system, constructed according to some embodiments;

[0017] Figure 11 A schematic diagram is shown of a machine learning process implemented by a machine learning unit of an EUV control system, constructed according to some embodiments;

[0018] Figure 12 This is a schematic diagram of a process constructed according to some embodiments, which involves collecting data, analyzing the collected data, extracting information from the analysis, and controlling the lithography system for enhanced lithography processes using an EUV control system.

[0019] Figure 13 A schematic diagram is shown illustrating a data process constructed according to some embodiments, including data collection, modeling, and analysis of the collected data;

[0020] Figure 14 Applications constructed according to some embodiments Figure 1 A flowchart of the method for an EUV lithography system. Detailed Implementation

[0021] The following disclosure provides a number of different embodiments or instances for implementing different features. Reference numerals and / or letters can be repeated used throughout the various examples described herein. This repetition is for simplicity and clarity and is not itself indicative of a relationship between the various disclosed embodiments and / or configurations. Further, specific instances of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the present application in any way. For example, in the following description, a first component formed over or on a second component can include embodiments where the first component and the second component are in direct contact, and can also include embodiments where additional components can be formed between the first component and the second component such that the first component and the second component can not be in direct contact. Further, in the present disclosure, the formation of a first feature on, connected to, and / or coupled to a second feature can include embodiments where the first feature and the second feature are formed in direct contact, and can also include embodiments where additional features are formed interposed the first feature and the second feature such that the first feature and the second feature can not be in direct contact.

[0022] Further, the present disclosure can repeat reference numerals and / or letters in each example. This repetition is for the purpose of simplicity and clarity and is not indicative of a relationship between the various disclosed embodiments and / or configurations. Further, in the following description, the formation of a first feature on, connected to, and / or coupled to a second feature can include embodiments where the first feature and the second feature are formed in direct contact, and can also include embodiments where additional features can be formed interposed the first feature and the second feature such that the first feature and the second feature can not be in direct contact. Additionally, spatially relative terms, such as "under", "below", "lower", "above", "upper", "proximate", "distal", and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the drawings. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the drawings. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. It is to be understood that the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Further, to the extent that the terms "approximately" or "about" are used in the description and claims, such terms are intended to encompass numbers within a reasonable range of the number recited, such as within + / - 10% of the recited number or other value as understood by one of ordinary skill in the art.

[0023] The present invention relates to an extreme ultraviolet (EUV) lithography apparatus integrated with an EUV control system designed to monitor, analyze, adjust, and control the EUV lithography apparatus for improved performance. The present invention also includes a method that uses the control system to monitor laser beams, plasma, contamination, EUV radiation, collect 3D diagnostic data thereof, analyze (including correlation and machine learning), identify root causes, and actively adjust and control parameters of the EUV lithography apparatus such that the lithography process is improved when the EUV lithography apparatus is used for integrated circuit (IC) manufacturing. In particular, the method and EUV control system are relevant to EUV lithography apparatuses used to pattern IC structures in advanced technology nodes. According to various embodiments, the IC structures can include field effect transistors (FETs), finFETs, or multi-gate devices such as gate-all-around (GAA) devices.

[0024] Figure 1 is a block diagram of a lithography system 10 constructed in accordance with some embodiments. The lithography system 10 can also be referred to as a scanner, which is operable to implement a lithography exposure process using a corresponding radiation source and exposure mode. In the present embodiment, the lithography system 10 is an extreme ultraviolet (EUV) lithography system designed to expose a resist layer with EUV radiation. The resist layer is a suitable material that is sensitive to EUV radiation. The lithography system 10 includes one or more EUV lithography apparatuses 12 designed to implement an exposure process using EUV radiation. The EUV lithography apparatus 12 includes an EUV source 14 (or simply source vessel 14) for generating EUV radiation 18, and an exposure chamber 16 designed to implement a lithography exposure process using the EUV radiation 18.

[0025] The radiation source 14 includes an enclosed space maintained in a hydrogen environment to protect and reduce contamination. The radiation source 14 includes various components configured to generate the EUV radiation 18. In the disclosed embodiment, the radiation source 14 includes a laser source 20 for providing a laser beam, a laser-produced plasma (LPP) module 22 for generating a plasma using the laser beam, and an EUV module 24 for collecting and focusing the EUV radiation 18 generated by the plasma. The exposure chamber 16 is maintained in a vacuum environment to reduce unwanted absorption of the EUV radiation 18. According to various embodiments, the exposure chamber 16 can include a mask table 28 for securing a photomask (or reticle), a wafer table 30 for securing a semiconductor substrate (e.g., a wafer), and EUV optics 26 designed to modulate the EUV radiation such that an image of a pattern or portion of a pattern defined on the photomask is directed onto the semiconductor substrate, or specifically, onto a resist layer coated on the semiconductor substrate.

[0026] The lithography system 10 also includes a control system (or EUV control system) 32 integrated with the EUV lithography apparatus 12. The control system 32 is designed with mechanisms to monitor various parameters of the EUV lithography apparatus 12, collect 3D diagnostic data about the EUV lithography apparatus 12, analyze the collected 3D data, identify root causes of any undesired issues, and proactively adjust and control variables of the EUV lithography apparatus 12 such that the EUV lithography apparatus 12 and corresponding processes are improved and enhanced when the EUV lithography apparatus 12 is applied in integrated circuit (IC) manufacturing.

[0027] The EUV control system 32 includes various units, modules, and components that are integrated and configured to perform various functions. Portions of the EUV control system 32 can be distributed in multiple locations, for example, partially embedded and configured in the EUV lithography apparatus 12 or partially standing along and coupled with the EUV lithography apparatus 12 through internet communication (e.g., internet cable connection, WiFi connection, Bluetooth connection, other suitable connection, or combination thereof).

[0028] The EUV control system 32 includes various monitors 34 to monitor and collect various information related to the EUV lithography apparatus 12 or specifically the radiation source 14 of the EUV lithography apparatus 12. In the disclosed embodiment, the EUV control system 32 includes a laser monitor 34A configured and designed with mechanisms to monitor the laser beam generated from the laser source 20, a plasma monitor 34B configured and designed with mechanisms to monitor the plasma generated by the laser beam, and an EUV monitor 34C configured and designed with mechanisms to monitor the EUV radiation 18 generated from the plasma. In some embodiments, the EUV control system 32 includes multiple sets of the above monitors (34A, 34B, and 34C), each set embedded in one corresponding EUV lithography apparatus 12 and connected to other components of the EUV control system 32. The EUV control system 32 can additionally or alternatively include one or more other monitors configured and designed to monitor other parameters (e.g., target droplet contamination and plasma stability) that will be collected and used to analyze the radiation source 14.

[0029] In particular, the various monitors 34 are designed and configured to collect 3D data related to the radiation source 14, which more effectively provides additional and sufficient information for analysis regarding the radiation source 14. Accordingly, the monitors 34 can be collectively referred to as 3D diagnostic modules (3DDMs) 34. 3D refers to the ability of the modules 34 to monitor and collect data in three or more dimensions, such as two spatial dimensions plus a time dimension, three spatial dimensions, or three spatial dimensions plus a time dimension. When the time dimension is considered, data is collected over a period of time in addition to data collected regarding spatial variations of the corresponding parameter (e.g., laser intensity, plasma intensity, or EUV radiation intensity). The 3DDMs 34 provide a path to construct 3D diagnostic models with sufficient and relevant data for enhanced analysis, such as correlation analysis between laser profile, plasma distribution, and EUV radiation.

[0030] As described above, the 3DDMs 34 include various units to monitor and collect different signals related to the EUV source. In particular, the 3DDMs 34 are designed to collect 3D data, which can be achieved through various available or future developed techniques.

[0031] The laser monitor 34A includes any suitable technology sensitive to the laser light from the laser source 20. In some embodiments, the laser monitor 34A includes one or more photodiodes sensitive to the laser beam from the laser source 20 and configured to receive the laser beam. In particular, the laser monitor 34A is capable of collecting 3D data of the laser beam. For example, the laser monitor 34A includes a plurality of photodiodes configured in an array with a configuration capable of effectively capturing and collecting the laser beam from the laser source 20. In other embodiments, the laser monitor 34A includes other suitable detectors (sensitive to the laser beam from the laser source 20), such as a photomultiplier tube, an optical isolator, an integrated optical circuit (IOC) element, a photoresistor, a vidicon, a charge-coupled imager, an injection laser diode, a quantum cascade laser, a photoemissive camera tube, or a combination thereof.

[0032] The plasma monitor 34B includes any suitable technology sensitive to the plasma generated by the laser beam of the laser source 20 through the LPP module 22. In some embodiments, the plasma monitor 34B includes one or more Faraday cups sensitive to the plasma (e.g., plasma density) generated by the laser beam and configured to effectively monitor the plasma. In particular, the plasma monitor 34B is capable of collecting 3D data of the plasma, such as a plasma density profile. For example, the plasma monitor 34B includes a plurality of Faraday cups configured in an array having a configuration capable of effectively collecting the plasma generated from the LPP module 22. In other embodiments, the plasma monitor 34B includes other suitable detectors (sensitive to plasma density), such as a light scattering detector, electron multiplier, or combination thereof.

[0033] The EUV monitor 34C includes any suitable technology sensitive to the EUV radiation 18 generated from the plasma. In some embodiments, the EUV monitor 34C includes one or more photodiodes sensitive to the EUV radiation 18 and configured to receive the EUV radiation 18. The mechanism of the sensing unit of the EUV monitor 34C can be similar to that of the sensing unit of the laser monitor 34A in that both sense photons, but of different spectral ranges. In some examples, the EUV monitor 34C includes a plurality of photodiodes configured in an array having a configuration capable of effectively collecting the EUV radiation 18 from the plasma (e.g., specifically from the EUV collector). In other embodiments, the EUV monitor 34C includes other suitable detectors (sensitive to the EUV radiation 18), such as a photomultiplier tube, a photoresistor, a hybrid pixel detector, other suitable device, or combination thereof.

[0034] Still referring to Figure 1EUV control system 32 also includes other modules, such as an analysis module 40, a control module 42, and a database 44 integrated with 3DDM 34. Database 44 is coupled with 3DDM 34 such that 3D data collected by 3DDM 34 is transmitted to and stored in database 44. Analysis module 40 is coupled with database 44 such that 3D data from 3DDM 34 is accessed by analysis module 40. Analysis module 40 is designed with one or more mechanisms to effectively analyze the 3D data and find the root cause of any problems associated with radiation source 14. Control module 42 is coupled with analysis module 40 and further coupled with EUV lithography apparatus 12. Control module 42 is designed with one or more suitable mechanisms to control radiation source 14 of EUV lithography apparatus 12 based on the results from analysis module 40. In some examples, control module 42 adjusts radiation source 14 of EUV lithography apparatus 12 such that EUV lithography apparatus 12 is adjusted to eliminate or reduce the identified problems, thereby improving and enhancing the EUV exposure process using EUV lithography apparatus 12.

[0035] Figure 2 is a schematic diagram of various modules of partial lithography system 10 constructed in accordance with some embodiments. In particular, Figure 2 EUV lithography apparatus 12 and monitor module 34 are shown. In particular, monitor module 34 of EUV control system 32 is embedded in EUV lithography apparatus 12 and integrated with EUV lithography apparatus 12.

[0036] Reference is made to Figure 2 EUV lithography apparatus 12 is further described. In the present embodiment, EUV lithography apparatus 12 is an EUV lithography tool designed to expose a resist layer by EUV radiation. The resist layer is a suitable material sensitive to EUV radiation. Lithography apparatus 12 employs radiation source 14 to generate EUV radiation 18, such as EUV light having a wavelength range between about 1 nm and about 100 nm. In the depicted embodiment, radiation source 14 generates EUV light having a center wavelength of about 13.5 nm. In further embodiments, the center wavelength of 13.5 nm has a full width at half maximum (FWHM) bandwidth of 1%. Accordingly, radiation source 14 is also referred to as EUV radiation source 14. In the present embodiment, EUV radiation source 14 utilizes a mechanism of laser-produced plasma (LPP) to generate EUV radiation 18. In particular, radiation source 14 includes a laser source 20, an LPP module 22, and an EUV module 24, as described above in Figure 1

[0037] ​The EUV lithography apparatus 12 also employs a mirror 50. In various embodiments, the mirror 50 includes various refractive optical components, such as a single lens or a lens system having multiple lenses (a waveband plate), or alternatively reflective optics (for EUV lithography systems), such as a single mirror or a mirror system having multiple mirrors, to direct light from the radiation source 14 onto the mask stage 28. In the present embodiment, where the radiation source 14 generates light in the EUV wavelength range, reflective optics are employed.

[0038] The EUV lithography apparatus 12 includes a mask stage 28 configured to hold the mask 52. In some embodiments, the mask stage 28 includes an electrostatic chuck (e-chuck) to hold the mask 52. This is because gas molecules absorb EUV light, so the EUV exposure chamber 16 is maintained in a vacuum environment to avoid loss of EUV intensity. In the present disclosure, the terms mask, reticle, and photomask are used to refer to the same component. In the present embodiment, the EUV lithography apparatus 12 is an EUV lithography system, and the mask 52 is a reflective mask. An exemplary structure of the mask 52 is provided for illustration. The mask 52 includes a substrate having a suitable material, such as a low thermal expansion material (LTEM) or fused silica. In various examples, the LTEM includes TiO2doped with SiO2, or other suitable materials having low thermal expansion. The mask 52 includes a reflective multilayer (ML) deposited on the substrate. The ML includes a plurality of thin film pairs, such as molybdenum-silicon (Mo / Si) thin film pairs (e.g., with a molybdenum layer on top of or beneath a silicon layer in each film pair). Alternatively, the ML can include molybdenum-beryllium (Mo / Be) thin film pairs, or other suitable materials configured to be highly reflective to EUV light. The mask 52 can also include a capping layer disposed on the ML to protect the ML from oxidation, such as ruthenium (Ru). The mask 52 also includes an absorber layer, such as a tantalum boron nitride (TaBN) layer, deposited over the ML. The absorber layer is patterned to define layers of an integrated circuit (IC). Alternatively, another reflective layer can be deposited over the ML and patterned to define layers of an integrated circuit, forming an EUV phase shift mask.

[0039] The EUV lithography apparatus 12 also includes a projection optics module (or projection optics box (POB)) 54 for imaging the pattern of the mask 52 onto a semiconductor substrate 56 held on a substrate stage 30 of the EUV lithography apparatus 12. In the present embodiment, the POB 54 has reflective optics for projecting EUV light. EUV light carrying an image of a pattern defined on the mask 52 is directed from the mask 52 and collected by the POB 54. The mirror 50 and the POB 54 are collectively referred to as an optical module of the EUV lithography apparatus 12.

[0040] The EUV lithography apparatus 12 also includes a substrate table (or wafer table) 30 to hold a semiconductor substrate 56. In the present embodiment, the semiconductor substrate 56 is a semiconductor wafer, such as a silicon wafer or other type of wafer to be patterned. In the present embodiment, the semiconductor substrate 56 is coated with a layer of resist that is sensitive to a radiation beam such as EUV light. Various components, including those described above, are integrated together and are operable to carry out an EUV lithography exposure process.

[0041] In some embodiments, the 3DDM 34 or portions of the 3DDM 34 are embedded in the EUV lithography apparatus 12 and integrated with the EUV lithography apparatus 12, with configurations and mechanisms to monitor various parameters of the radiation source 14. In various embodiments, the 3DDM 34 includes a laser monitor 34A, a plasma monitor 34B, an EUV monitor 34C, other suitable monitors, or combinations thereof.

[0042] In some embodiments, the monitor module 34 includes a laser monitor 34A configured to monitor the laser beam, such as the laser beam (spatial) profile and changes in the laser beam profile over time.

[0043] In some embodiments, the monitor module 34 includes a plasma monitor 34B configured to monitor the plasma, such as the plasma spatial distribution and changes in the plasma distribution over time.

[0044] In some embodiments, the monitor module 34 includes an EUV monitor 34C configured to monitor the EUV radiation, such as the EUV radiation (spatial) profile and changes in the EUV radiation profile over time.

[0045] In some embodiments, the plasma monitor 34B is designed with mechanisms to additionally or alternatively monitor the plasma stability of the plasma. The plasma state of the radiation source 14 changes over time. For example, the target material is used to generate the plasma, and the state of the target material changes over time, such as droplet size, ionization rate from the target material (to be described below), and the plasma concentration changes accordingly. Changes in the plasma state also result in changes in the EUV intensity in the lithography exposure process. In some examples, the monitoring of the plasma state is a separate monitor dedicated to monitoring the plasma stability.

[0046] In some examples, the monitor module 34 includes a utility monitor having a mechanism to monitor the utility of the target material droplets in a dose margin. The utility monitor tracks historical data of the utility of the target material droplets for semiconductor wafers previously processed in the EUV lithography apparatus 12. Alternatively, the utility monitor is integrated in the plasma monitor 34B to monitor various parameters related to the plasma. The dose margin and other terms will be further described at a later stage.

[0047] In some other embodiments, the functions of the plasma monitor 34B can be implemented by the EUV monitor 34C. For example, the dose error is related to plasma instability, by monitoring the EUV energy by the EUV monitor 34C, the dose error can be extracted from the monitored EUV energy. The EUV lithography apparatus 12 can also include or be integrated with (or coupled to) other modules.

[0048] In some embodiments, the EUV lithography apparatus 12 includes a gas supply module designed to provide hydrogen gas to the radiation source 14, which effectively protects the radiation source 14 (e.g. the collector) from contamination. In other embodiments, the EUV lithography apparatus 12 includes magnets configured to guide the plasma by respective magnetic fields.

[0049] In particular, the radiation source 14, which is constructed in accordance with some embodiments, is shown in a schematic manner in Figure 3The radiation source 14 employs a laser-produced plasma (LPP) mechanism to produce plasma, and further to generate EUV light from the plasma. The radiation source 14 includes one or more lasers 20, such as pulsed carbon dioxide (C02) lasers, to generate laser beams 62. In one illustrative embodiment, the laser source 20 includes two laser devices, one to generate a pre-pulse to impinge on a target material 68, and another to generate a main pulse to impinge on the target material 68. The laser 20 can also include one or more laser amplifiers to further amplify the power of the laser beams. In the disclosed embodiment, the two laser devices can each include a laser amplifier or alternatively share a laser power. The laser beams 62 are directed through an output window 64 that is integrated with a collector (also referred to as an LPP collector or an EUV collector) 66. The output window 64 employs a suitable material that is substantially transparent to the laser beams. The collector 66 is designed with a suitable coating material and shape to act as a mirror for EUV collection, reflection, and focusing. In some embodiments, the collector 66 is designed to have an elliptical geometry with two foci, such as a main focus and an intermediate focus. In some embodiments, the coating material of the collector 66 is similar to the reflective multilayer of the EUV mask 52. In some examples, the coating material of the collector 66 includes MLs (e.g., multiple Mo / Si thin film pairs), and can further include a capping layer (e.g., Ru) coated on the MLs to substantially reflect the EUV light. In some embodiments, the collector 66 can also include a grating structure designed to effectively scatter the laser beams directed onto the collector 66. For example, a silicon nitride layer is coated on the collector 66, and the silicon nitride layer is patterned to have a grating pattern.

[0050] The laser beams 62 are directed to heat the target material 68, thereby creating a high-temperature plasma that further generates the EUV radiation (or EUV light) 18. In the present embodiment, the target material 68 is tin (Sn). The target material 68 is delivered in the form of droplets. Those target material droplets (e.g., tin droplets) are also referred to simply as droplets. The EUV radiation 18 is collected by the collector 66. The collector 66 further reflects and focuses the EUV radiation for the lithographic exposure process.

[0051] The radiation source 14 is configured in an enclosed space, referred to as a source vessel. The source vessel is maintained in a vacuum environment since air absorbs EUV radiation. In some embodiments, the source vessel is also provided with hydrogen gas for protecting the source vessel from contamination. In some embodiments, the 2DDM 34 is embedded in the radiation source, and is configured to monitor various parameters of the radiation source.

[0052] The radiation source 14 can also include more other components integrated together, such as those shown in Figure 4 Figure 4 ​is a schematic diagram of a radiation source 14 constructed in accordance with some embodiments. The radiation source 14 employs an LPP mechanism. The radiation source 14 includes a laser 20, such as a pulsed CO2laser, to generate a laser beam 62. The laser beam 62 is directed by a beam delivery system 72, such as one or more mirrors configured, to a focusing lens 74 to focus the laser beam 62. The laser beam 62 is further projected through an output window 64 integrated with a collector 66. The laser beam 62 is focused into a target material 68, such as a tin droplet 68, in a focal point of the collector 66, thereby creating a high-temperature plasma. The tin droplet 68 is generated by a tin droplet generator 76. A tin catcher 78 is further configured to catch the tin droplet. The high-temperature plasma thus created further generates EUV radiation 18, which is collected by the collector 66. The collector 66 further reflects the EUV radiation and focuses it to an intermediate focus, and further directs it for an EUV exposure process.

[0053] The pulses of the laser 20 and the droplet generation rate of the tin droplet generator 76 are controlled to remain synchronized so that the tin droplet 68 continuously receives peak power from the laser pulses of the laser 20. In some examples, the frequency of the tin droplet generation ranges from 20 kHz to 100 kHz. For example, the laser 20 includes a laser circuit designed to control the generation of the laser pulses. The laser circuit and the tin droplet generator 76 are coupled so that the generation of the laser pulses and the generation of the tin droplet 68 remain synchronized.

[0054] In some embodiments, the radiation source 14 further includes a central shield 79 designed and configured to shield the laser beam 62. The radiation source 14 can also include an intermediate focus (IF)-overlapping module 80, such as an IF-fast overlapping-connection module, configured to direct the EUV radiation 18 to an intermediate focus 81 with enhanced conversion gain. The IF-overlapping module 80 can additionally function to shield the laser beam 62 for improved performance.

[0055] The radiation source 14 can further be integrated or coupled with other units / modules. For example, a gas supply module is coupled with the radiation source 14 to provide hydrogen gas for various protection functions, including effectively protecting the collector 66 from contamination caused by tin particles (tin debris).

[0056] The target material droplets 68 and the EUV radiation 18, and the corresponding mechanisms, are further illustrated in Figure 5 The target material droplets 68 are grouped into droplet strings 82, which are separated by intervening times and intervening droplets 84. In the present embodiment, the intervening droplets 84 are not excited by the laser beam 62 during the EUV exposure process.

[0057] During the EUV exposure process, a series of droplet strings 82 are provided in the radiation source 14. Each droplet string 82 includes a plurality of target material droplets 68 and is configured to provide a specific EUV energy (referred to as the droplet string target energy or BTE) during the EUV exposure process. When the semiconductor substrate 56 is exposed using the EUV energy by the lithography system 10, an exposure dose can be reached at each droplet string 82 when the EUV energy contribution from the droplet string target energy. The target material droplets 68 in each droplet string can be defined into two categories: dose droplets 86 and margin droplets 88. During the EUV exposure process, the dose droplets 86 in each droplet string 82 are excited by the laser to generate a plasma and accordingly the EUV radiation generated by the plasma has the EUV energy reaching the droplet string target energy. The margin droplets 88 in each droplet string 82 are reserved for dose control and serve as a backup for the dose droplets to maintain the EUV energy of the droplet string to reach the droplet string target energy. The margin droplets 88 are collectively referred to as dose margin. Due to the instability of the plasma intensity, not all droplets contribute the nominal EUV energy. For example, when the laser-generated plasma from one dose droplet has a smaller density, the EUV energy collected from that dose droplet will be lower than the normal level. When the EUV energy generated from the dose droplets 86 in the droplet string 82 cannot reach the droplet string target energy, the margin droplets 88 or a subset thereof are excited to contribute additional EUV energy so that the total EUV energy from the droplet string 82 reaches the droplet string target energy. The number of target material droplets in each droplet string is Nt. The number of dose droplets 86 in each droplet string is designed to be Nd, and the number of margin droplets in each droplet string is designed to be Nm. The relationship between these parameters is Nt = Nd + Nm. Therefore, when Nt is given, increasing the dose margin reduces the droplet string target energy.

[0058] In some embodiments, the laser source 20 can include two or more laser devices such that the two or more laser devices are configured in a manner that the respective laser beams 62 are sequentially directed to the target material droplets (e.g., Sn droplets) 68 as the droplets move from the droplet generator 76 to the droplet collector 78. Thus, the energy from the laser beams from different laser devices is accumulated to reach a target value such that the laser-generated plasma is able to generate the desired EUV radiation. This will be further described with reference to Figure 6 Figure 6 is a schematic diagram of the process of droplet 68 interaction with the laser beam, and from the laser to the plasma and further to the EUV radiation, constructed in accordance with some embodiments. The horizontal axis 94 indicates time (not to scale) or the progress of the EUV generation over time.

[0059] As Figure 6 ​As shown, a target material droplet 68, such as a spherical liquid tin droplet, is impacted by a first laser beam (laser pre-pulse or PP) and changes its shape, such as a pancake shape, by its path. Later, a second laser beam (laser main pulse or MP) impacts the target material droplet 68 and turns it into a plasma 91 (e.g., tin plasma or Sn plasma), which further generates EUV radiation 18. At the same time, debris 92 is also generated from the plasma in various forms, such as Sn particles, and further deposits on the surface of the EUV collector 66, causing contamination, which will reduce the reflectivity of the EUV collector 66, causing more equipment downtime of the lithography system 10, thus increasing manufacturing cost. The energy conversion process includes conversion from laser energy to plasma energy, and from plasma energy to EUV energy. Between the PP and the MP, as shown in the region between t1 and t2 in Figure 6 As shown, a target material droplet 68, such as a spherical liquid tin droplet, is impacted by a first laser beam (laser pre-pulse or PP) and changes its shape, such as a pancake shape, by its path. Later, a second laser beam (laser main pulse or MP) impacts the target material droplet 68 and turns it into a plasma 91 (e.g., tin plasma or Sn plasma), which further generates EUV radiation 18. At the same time, debris 92 is also generated from the plasma in various forms, such as Sn particles, and further deposits on the surface of the EUV collector 66, causing contamination, which will reduce the reflectivity of the EUV collector 66, causing more equipment downtime of the lithography system 10, thus increasing manufacturing cost. The energy conversion process includes conversion from laser energy to plasma energy, and from plasma energy to EUV energy. Between the PP and the MP, as shown in the region between t1 and t2 in Figure 6 As shown, a target material droplet 68, such as a spherical liquid tin droplet, is impacted by a first laser beam (laser pre-pulse or PP) and changes its shape, such as a pancake shape, by its path. Later, a second laser beam (laser main pulse or MP) impacts the target material droplet 68 and turns it into a plasma 91 (e.g., tin plasma or Sn plasma), which further generates EUV radiation 18. At the same time, debris 92 is also generated from the plasma in various forms, such as Sn particles, and further deposits on the surface of the EUV collector 66, causing contamination, which will reduce the reflectivity of the EUV collector 66, causing more equipment downtime of the lithography system 10, thus increasing manufacturing cost. The energy conversion process includes conversion from laser energy to plasma energy, and from plasma energy to EUV energy. Between the PP and the MP, as shown in the region between t1 and t2 in Figure 6 As shown, a target material droplet 68, such as a spherical liquid tin droplet, is impacted by a first laser beam (laser pre-pulse or PP) and changes its shape, such as a pancake shape, by its path. Later, a second laser beam (laser main pulse or MP) impacts the target material droplet 68 and turns it into a plasma 91 (e.g., tin plasma or Sn plasma), which further generates EUV radiation 18. At the same time, debris 92 is also generated from the plasma in various forms, such as Sn particles, and further deposits on the surface of the EUV collector 66, causing contamination, which will reduce the reflectivity of the EUV collector 66, causing more equipment downtime of the lithography system 10, thus increasing manufacturing cost. The energy conversion process includes conversion from laser energy to plasma energy, and from plasma energy to EUV energy. Between the PP and the MP, as shown in the region between t1 and t2 in

[0060] Figure 7 is a block diagram of the EUV control system 32 constructed in accordance with some embodiments. Figure 1 The 3DDM 34 is described in more detail in

[0061] In some embodiments, the 3DDM 34 can further include a contamination monitor 34D designed with a mechanism to detect contamination from a target material, such as Sn particles, when a plasma is generated by the laser beam. Those Sn particles can be generated when a plasma is generated by the laser beam and can deposit on the surface of the EUV collector 66, thereby causing contamination and reducing the EUV reflectivity of the EUV collector 66. In some embodiments, the contamination monitor 34D includes one or more photodiodes that are sensitive to the laser beam from the laser source 20 and configured to receive the laser beam. In particular, the laser monitor 34A is capable of collecting 3D data of the laser beam. For example, the laser monitor 34A includes a plurality of photodiodes configured in an array having a configuration that is effective to capture and collect the laser beam from the laser source 20. In other embodiments, the laser monitor 34A includes other suitable detectors (sensitive to the laser beam from the laser source 20), such as a photomultiplier tube, a photoisolator, an integrated optical circuit (IOC) element, a photoresistor, a photoconductive camera tube, a charge-coupled imaging device, an injection laser diode, a quantum cascade laser, a photoemissive camera tube, or a combination thereof.

[0062] The plasma monitor 34B includes any suitable technology that is sensitive to the plasma generated by the laser beam from the laser source 20 through the LPP module 22. In some embodiments, the plasma monitor 34B includes one or more Faraday rings that are sensitive to the plasma (e.g., plasma density) generated by the laser beam and configured to effectively monitor the plasma. In particular, the plasma monitor 34B is capable of collecting 3D data of the plasma, such as a plasma density profile. For example, the plasma monitor 34B includes a plurality of Faraday rings configured in an array having a configuration that is effective to collect the plasma generated from the LPP module 22. In other embodiments, the plasma monitor 34B includes other suitable detectors (sensitive to the plasma density), such as a light scattering detector, an electron multiplier, or a combination thereof.

[0063] The EUV monitor 34C includes any suitable technology that is sensitive to the EUV radiation 18 generated from the plasma. In some embodiments, the EUV monitor 34C includes one or more photodiodes that are sensitive to the EUV radiation 18 and configured to receive the EUV radiation 18. The mechanism of the sensing unit of the EUV monitor 34C can be similar to that of the sensing unit of the laser monitor 34A, as both sense photons, albeit of different spectral ranges. In some examples, the EUV monitor 34C includes a plurality of photodiodes configured in an array, with a configuration that is capable of efficiently collecting the EUV radiation 18 from the plasma, e.g., specifically from the EUV collector reflection. In other embodiments, the EUV monitor 34C includes other suitable detectors that are sensitive to the EUV radiation 18, such as photomultiplier tubes, photoresistors, hybrid pixel detectors, other suitable devices, or combinations thereof.

[0064] The EUV control system 32 further includes an analysis module 40, a control module 42, and a database 44. The various parameters of the radiation source 14 are monitored and collected by the 3DDM 34, saved in the database 44, analyzed by the analysis module 40, and fed back to the control module 42 for controlling the radiation source 14 for the enhanced lithography system 10 and the improved lithography process implemented by the lithography system 10.

[0065] The database 44 includes a physical structure, e.g., a memory device, with inputs and outputs for data transfer in and out. Examples of the memory device include a non-volatile memory (NVM) device such as a flash memory device or a ferroelectric random access memory (RAM), a volatile memory such as a static RAM (SRAM) device, other suitable memory devices, or combinations thereof. The database 44 includes various sections for storing various data, such as a database section 44A for laser profile data, a database section 44B for target contamination data, a database section 44C for plasma distribution data, a database section 44D for EUV radiation data, and a database section 44E for analysis data. The database 44 can further include other suitable database sections for various data associated with the radiation source 14 or even the EUV lithography apparatus 12.

[0066] The analysis module 40 includes various correlation analysis sections 40A that analyze correlations between various parameters, such as the correlation between the laser beam profile and the plasma distribution, the correlation between the plasma distribution and the EUV radiation energy, the correlation between the laser beam profile and the target material debris, the correlation between the laser beam profile and the EUV energy, and other correlations.

[0067] Figure 8A relevant example is shown and described in detail below. Figure 8 (a) is a laser beam profile in terms of intensity (I) of the laser beam versus the XY surface. The XY surface is defined as Figure 3 the surface in (b). The laser beam is directed along the Z direction from the laser source 20 to the target material 68, while the X and Y directions are two orthogonal directions defined in a Cartesian coordinate system. The XY surface is defined as a plane intersecting the Z axis at the location of the target material droplet 68. The corresponding profile of the laser beam is also shown in Figure 8 (b). Two axes represent X and Y, while the other axis represents the intensity (I) of the laser beam. The corresponding distribution or profile of the laser beam is further shown in Figure 8 (c). One axis represents X, while the other axis represents the intensity (I) of the laser beam. Two exemplary profiles 96 and 98 are shown in Figure 8 (c). The first profile 96 of the laser beam has a Gaussian distribution, and the second profile 98 of the laser beam has a non-uniform distribution different from the Gaussian distribution. In the disclosed embodiments, the first profile 96 of the laser beam results in a better and less debris of the generated plasma 91, and further results in a higher EUV radiation 18 with a greater conversion efficiency (CE); while the second profile 98 of the laser beam results in a weak and more debris of the generated plasma 91, and further results in a degraded EUV radiation 18 with a lower CE. In the present example, the laser beam profile is correlated with the plasma profile, the debris, and the EUV radiation energy. Such correlation provides information and indication of how to adjust (e.g. the laser beam profile) for enhanced EUV radiation and reduced debris.

[0068] The analysis module 40 also includes various tool matching units 40B that collect and analyze various parameters, such as the laser beam profile, the plasma distribution, the EUV radiation energy, and the debris count of various lithography systems, in order to extract useful information that is feedback for adjusting and controlling the lithography systems for enhanced EUV radiation and reduced debris.

[0069] Figure 9 An example is shown and described in detail below. Data is collected from various lithography tools, and compared according to the laser beam and plasma distribution. Figure 9 Laser beam profiles for various lithography systems, such as Tool A to Tool E, are shown. In particular, the laser beam profiles for each tool are collected from three different stages: the pre-pulse laser beam at the target material 68; the main pulse laser beam after the laser amplifier; and the main pulse laser beam at the target material 68. Various beam profiles from the respective lithography systems and respective stages are shown in Figure 9Each one can be different from each other, such as circular, off-center, peanut-shaped, asymmetric profile, etc. Note that these are for illustration purposes only. Corresponding plasma distributions are further collected from those lithography systems. EUV radiation energy and CE can be further collected from those lithography systems. Those data are then analyzed to find the relationship between the laser beam profile and the plasma distribution, or even the relationship between the plasma distribution and the EUV radiation. In particular, the relationship between the laser beam profile and the plasma distribution is further mapped to each of the above three laser beam profiles.

[0070] In some embodiments, the above analysis yields the following results. Each lithography system has a specific laser beam profile, which results in different plasma thermodynamics and nonlinear effects during the laser-plasma evolution. Greater laser intensity regions provide greater EUV radiation and greater CE. Lower laser intensity regions result in insufficient heating and plasma generation, which results in more target material (e.g., Sn) debris. Other analyses include comparing the similarity of the laser beams between different lithography systems; and the correlation between the laser beam profile and the EUV radiation energy. Those results can be further used in a feedback loop to control and adjust the laser source, including laser realignment, focusing of the laser beam, and timing control to synchronize the target material droplet 68 and the pulses of the laser source.

[0071] The analysis module 40 also includes various modeling units 40C that establish corresponding models (e.g., laser beam model, plasma model, EUV radiation model, or target material contamination model) from the collected data for further analysis (e.g., correlation analysis). For example, the correlation analysis can include two stages. In the first stage, the raw data collected from the 3DDM 34 are first processed to filter out irrelevant data or noise, generating pre-processed data, also referred to as models of the laser beam, plasma, or EUV radiation. In the second stage, the pre-processed data are sent to the correlation unit 40A for correlation analysis, including the correlation between the laser beam profile, plasma distribution, EUV radiation energy, and target material debris.

[0072] Figure 10 An example is shown and described in detail below. In Figure 10 In (a), the laser beam profile is represented in a Cartesian coordinate system around the focused target material droplet 68. The number 102 represents the laser beam profile, while the number 104 represents the effective zone. The effective zone 104 represents the region in which the plasma generated by the laser beam 62 can effectively and efficiently produce EUV radiation 18, and maintain sufficient EUV energy in production, such as greater than a predetermined standard. In one example, the standard is an EUV radiation intensity of 5 mJ / m 3 This is shown inFigure 10 (b) is further illustrated. In the disclosed modeling method, only the effective region 104 is relevant and will be further analyzed. In further embodiments, the spatial distribution of EUV energy is further divided into a three-dimensional (3D) grid, such as a cubic grid in a 3D Cartesian coordinate system. These grids are evaluated individually using standard to determine the effective region. Other regions are removed and discarded, as Figure 10 (c) illustrates. The geometric center of the effective region 104 is marked with the numeral 106. Figure 10 (d) provides more examples of laser beam profiles 102 and corresponding effective regions 104. In this case, the target material droplet laser beam should be positioned at the center 106 of the effective region 104 for enhanced EUV radiation generation. This can be feedback for controlling and adjusting the synchronization of the laser beam 62 and the target material droplet 68. Further descriptions will be made below in connection with other units of the analysis module 40. Figure 10

[0073] The analysis module 40 also includes one or more machine learning units 40D that use one or more machine learning techniques, such as artificial neural networks, to analyze various collected or pre-processed data. In some embodiments, those data as training data using improved EUV radiation energy as the desired output are fed to the machine learning unit 40D so that the machine learning unit 40D identifies the optimized conditions to produce increased EUV radiation energy and reduced debris contamination. These conditions can be fed back to the control module 42 to adjust and tune the corresponding lithography system to the optimized conditions for enhanced lithography process.

[0074] One embodiment of the machine learning process by the machine learning unit 40D will be further described with reference to Figure 10 In this embodiment, a pre-set EUV energy standard is used as the desired output, the laser beam profile and corresponding EUV radiation energy are used as the training data, the machine learning unit 40D can identify the desired position of the target material droplet 68. In one illustrative example, the desired position of the target material droplet 68 is at the position (X=0.34 pm, Y=4.5 pm, and X=-112 pm), which can be provided to the control module 42 for adjustment.

[0075] The machine learning process by the machine learning unit 40D will be further described with reference to Figure 11 Figure 11 ​​A table is included that includes 4 examples in 4 columns. In the table, the second row includes the laser beam profile 102, the first row includes the effective area 104 of the laser beam, and the third row includes the machine learning results. For each example, the effective area 108 obtained by the machine learning process is provided, which is similar to the effective area obtained by the modeling method described above. The similarity 110 of both is provided in the fourth row. The results show a high degree of similarity, and both methods are effective.

[0076] Figure 12 A process is shown to collect data, analyze the collected data, extract information from the analysis, and control the lithography system for enhanced lithography processes by utilizing various modules of the EUV control system 32. In some examples, the data is collected by the monitor 34, and the collected data includes target data (position of the target material relative to the focal point of the laser beam), and 3D DM data of the laser beam profile, plasma distribution, and EUV radiation energy. The analysis is implemented by the analysis module 40, and can include modeling, correlation analysis, tool matching, machine learning, or a combination thereof. In one example, the analysis produces a correlation between the EUV radiation energy and the target position. The correlation results are further fed back to the control module 42 to adjust the laser source 20 (e.g., laser beam orientation and focus), and the timing of the target material droplets 68 such that the target position is adjusted to a position with increased or maximized EUV radiation energy. In particular, the effective area 104 is associated with higher vaporization, higher ion energy and higher EUV radiation energy, and less debris accumulation, while other areas are associated with lower vaporization, lower ion energy and lower EUV radiation energy, and more debris accumulation. The analysis also includes comparing the similarity between the laser beam profile and the effective area; comparing the 3D capture rate between the beam profile and the effective data area; and creating a time-resolved effective model to compare target maps.

[0077] Figure 13 Another data process is shown that includes collecting data, modeling, and analyzing the collected data. In Figure 13 In (a), the distribution of the plasma 91 is collected in a 3D mode. Statistical criteria such as 3σ are then used to fill in the scatter data, resulting in a pre-processed distribution (or pre-processed plasma distribution) 112 as shown in (b). The parameter σ is the standard deviation of the normal distribution. Data space 114 is then extracted from the pre-processed distribution 112 as shown in (c). The data space 114 defines the outer contour of the pre-processed distribution. The effective area 116 is determined in the data space 114 using appropriate analysis (e.g., correlation analysis, machine learning, other suitable methods, or a combination thereof) as shown in (d) and (e). Figure 13 Figure 13 Figure 13 Figure 13 ​​​(e) shown. In one illustrative example, the active region is a plasma region that produces sufficient EUV radiation energy. Additionally, the active region 116 is extracted from the data space 114, as shown in Figure 13 (f). The active region 116 provides information for controlling and adjusting the lithography system 10 for enhanced lithography processes. For example, the geometric center of the active region 116 is fed back to the control module 42 to adjust the alignment of the laser beam 62 and the timing of the target material droplet 68 for enhanced EUV radiation.

[0078] Referring back to Figure 7 , the control module 42 is further described in accordance with various embodiments. In some embodiments, the control module 42 includes a laser alignment unit 42A, a target position control unit 42B, a laser pulse delay adjustment unit 42C, and a container control unit 42D. The laser alignment unit 42A includes mechanisms to adjust the alignment of the laser beam so as to adjust the laser beam profile accordingly. The mechanisms of the laser alignment unit 42A include a stepper motor, a piezoelectric material, other suitable mechanisms, or a combination thereof, to adjust the alignment of the laser beam; an optical assembly to focus the laser beam so that the laser beam profile is optimized for increased EUV radiation.

[0079] The target position control unit 42B includes mechanisms to adjust the delivery of the target material droplet 68 so that the laser beam is focused on the appropriate location of the target material droplet 68. The mechanisms of the target position control unit 42B include circuitry to fine tune the delivery time.

[0080] The laser pulse delay adjustment unit 42C includes mechanisms to adjust the timing of the laser pulse so that the laser pulse (pre-pulse or main pulse) is generated at the appropriate timing so that the laser pulse is synchronized with the delivery of the target material droplet 68, thus allowing the pre-pulse laser beam or the main pulse laser beam to hit the appropriate location of the target material droplet 68. The mechanisms of the laser pulse delay adjustment unit 42C include circuitry to fine tune the laser device to generate the laser pulse at the appropriate time.

[0081] The vessel control unit 42D includes one or more mechanisms to adjust various parameters of the radiation source 14, such as vessel pressure, vessel gas flow rate, and vessel temperature, so that the laser beam 62, the plasma 91, and the EUV radiation 18 are optimized according to feedback from the data analysis. Those parameters are related to contamination and EUV radiation. For example, the vessel temperature is a parameter to control the evaporation of the target material, and thus affects contamination and EUV radiation energy. In another example, the vessel hydrogen flow rate and pressure are parameters to control contamination and EUV radiation energy of the target material. The mechanisms of the vessel control unit 42D include flow rate control devices to adjust the flow rate of the vessel gas, such as the hydrogen flow rate, circuitry to fine tune the delivery time; pressure sensors and flow control devices to adjust the flow of the vessel gas so that the vessel pressure is optimized; and thermal sensors and circuitry to control the power of the heater so that the vessel temperature is optimized for enhanced EUV radiation.

[0082] Figure 14 A flowchart of a method 120 for an EUV lithography process implemented by the lithography system 10 constructed in accordance with some embodiments is shown.

[0083] The method 120 includes an operation 122 of loading the EUV photomask 52 to the lithography system 10 operable to implement the EUV lithography exposure process. The photomask 52 includes an IC pattern to be transferred to a semiconductor substrate, such as the semiconductor wafer 56. The operation 122 can also include various steps, such as securing the photomask 52 on the mask table 28, and implementing alignment.

[0084] The method 120 includes an operation 124 of loading the wafer 56 to the lithography system 10. The wafer 56 is coated with a photoresist layer. In the present embodiment, the photoresist layer is sensitive to the EUV radiation 18 from the radiation source 14 of the lithography system 10.

[0085] The method 120 includes an operation 126 of controlling the lithography system 10, particularly adjusting the radiation source 14 for enhanced EUV radiation. The operation 126 also includes a plurality of steps (or sub-operations) to adjust and tune the lithography system 10 for enhanced lithography process. In the disclosed embodiment, the operation 126 includes a step 136 for collecting data of the radiation source 14 by the monitor module 34, a step 138 for analyzing the collected data by the analysis module 40, and a step 140 for adjusting the radiation source 14 by the control module 42 according to the analysis results obtained in the step 138.

[0086] In particular, in some embodiments, collecting data of the radiation source 14 by the monitor module 34 includes collecting data of a laser beam profile by the laser monitor 34A; collecting data of a plasma distribution by the plasma monitor 34B; collecting data of EUV radiation energy by the EUV monitor 34C; collecting data of Sn contamination by the Sn contamination monitor 34D; or a combination thereof. In some embodiments, analyzing the collected data by the analysis module 40 includes analyzing the collected data by the correlation analysis unit 40A; analyzing the collected data by the tool matching unit 40B; analyzing the collected data by the modeling unit 40C; analyzing the collected data by the machine learning unit 40D; or a combination thereof. Adjusting the radiation source 14 by the control module 42 includes adjusting a laser beam profile by the laser alignment unit 42A; adjusting delivery of target material droplets by the target position control unit 42B; adjusting synchronization of laser pulses (pre-pulse or main pulse) by the laser pulse delay adjustment unit 42C; adjusting container pressure, container gas flow rate, and / or container temperature by the container control unit 42D; or a combination thereof.

[0087] The method 120 includes an operation 128 of performing a lithography exposure process on the wafer 56 in the lithography system 10. In operation 128, the laser 20 and the tin droplet generator 68 are kept in synchronization (in particular, laser pulses and tin droplet generation are kept in synchronization) by appropriate mechanisms, such as control circuitry with timers to control and synchronize both. The synchronized laser 20 excites the target material droplet 68 and generates a plasma, thereby generating EUV radiation. During operation 128, the generated EUV radiation is irradiated on the photomask 52 (through the reflector 50) and further projected on a resist layer coated on the wafer 56 (through the POB 54), thereby forming a latent image on the resist layer. In the present embodiment, the lithography exposure process is performed in a scanning manner.

[0088] In particular, in the lithography exposure process, the target material droplet 68 is excited by the laser beam 62 to generate a plasma 91 and further generate EUV radiation 18. The various steps in 126 can be performed at the same time as or with overlapping time as the lithography exposure process. For example, data is collected by the monitor 34 in operation 136 and the collected data is analyzed by the analysis module 40 in operation 138.

[0089] The method 120 can include other operations to complete the lithography patterning process. For example, the method 120 can include an operation 130 of developing the exposed photoresist layer to form a photoresist pattern having a plurality of openings defined thereon. In one example, the photoresist layer is positive; the exposed portions of the photoresist layer are removed by the developer. In another example, the photoresist layer is negative; the exposed portions of the photoresist layer are retained; while the unexposed portions are removed by the developer.

[0090] In particular, after the lithographic exposure process of operation 128, the wafer 56 is transferred from the lithography system 10 to a developing unit to perform operation 130. The method 120 can further include other operations, such as various bake steps. As one example, the method 120 can include a post-exposure bake (PEB) step between operation 128 and operation 130.

[0091] The method 120 can further include other operations, such as operation 132 of performing a fabrication process on the wafer 56 through the openings of the photoresist pattern. In one example, the fabrication process includes performing an etching process on the semiconductor substrate 56 or a material layer thereon using the photoresist pattern as an etching mask. In another example, the fabrication process includes performing an ion implantation process on the semiconductor substrate 56 using the photoresist pattern as an implantation mask. After operation 132, the photoresist layer can be removed by wet stripping or plasma ashing.

[0092] The present disclosure provides an EUV lithography system with a 3D sensing and adjustment module. The EUV lithography system includes a 3D diagnostic module embedded in a radiation source container, and an analysis and control module that adjusts the radiation source according to the analysis of the 3D data of the radiation source. By implementing the disclosed EUV lithography system 10 and the method of its application, the EUV lithography system 10 is fine-tuned to increase EUV radiation energy, reduce debris contamination, and enhance the lithographic exposure process. The disclosed EUV lithography system 10 includes an EUV lithography tool integrated with an EUV control system 32, which further includes a monitor 34, an analysis module 40, a control module 42, and a database 44. The monitor 34 of the EUV control system 32 is embedded in a radiation source 14 of the EUV lithography apparatus 12. In some examples, the method includes collecting data of the radiation source 14 by the monitor 34, analyzing the collected data by the analysis module 40, and adjusting the radiation source 14 according to the analysis by the control module 42.

[0093] In one example aspect, the present disclosure provides a method for an extreme ultraviolet (EUV) lithography system, the EUV lithography system including a radiation source having a laser device configured with a mechanism to generate EUV radiation. The method includes: collecting a laser beam profile of a laser beam from the laser device in a 3-dimensional (3D) mode; collecting an EUV energy distribution of the EUV radiation generated by the laser beam in the 3D mode; performing an analysis on the laser beam profile and the EUV energy distribution to obtain analysis data; and adjusting the radiation source according to the analysis data to enhance the EUV radiation.

[0094] In some embodiments, the method for an extreme ultraviolet lithography system further includes: performing an extreme ultraviolet lithographic exposure process on a semiconductor substrate using the extreme ultraviolet lithography system with the adjusted radiation source.

[0095] In some embodiments, the method for an extreme ultraviolet lithography system further comprises: after the implementation of the extreme ultraviolet lithography exposure process, implementing a developing process on the semiconductor substrate, thereby forming a patterned photoresist layer on the semiconductor substrate; and implementing a manufacturing process on the semiconductor substrate through the openings of the patterned photoresist layer.

[0096] In some embodiments, the manufacturing process comprises one of an etching process and an ion implantation process.

[0097] In some embodiments, the extreme ultraviolet lithography system comprises an extreme ultraviolet lithography device, the extreme ultraviolet lithography device further comprises a radiation source; the extreme ultraviolet lithography system comprises an extreme ultraviolet control system integrated with the extreme ultraviolet lithography device; and the extreme ultraviolet control system comprises a monitoring module, an analysis module, and a control module, wherein the monitoring module is embedded in the radiation source.

[0098] In some embodiments, the monitoring module comprises a laser monitor, a plasma monitor, and an extreme ultraviolet monitor; the analysis module comprises a correlation analysis unit, a modeling unit, and a machine learning unit; and the control module comprises a laser alignment unit, a target position control unit, a laser pulse delay adjustment unit, and a container control unit.

[0099] In some embodiments, collecting a laser beam profile of a laser beam from a laser device in a 3-dimensional (3D) mode comprises collecting the laser beam profile of the laser beam by the laser monitor; collecting an extreme ultraviolet energy distribution of extreme ultraviolet radiation generated by the laser beam in a 3-dimensional mode comprises collecting the extreme ultraviolet energy distribution of the extreme ultraviolet radiation by the extreme ultraviolet monitor; and implementing analysis of the laser beam profile and the extreme ultraviolet energy distribution comprises implementing the analysis of the laser beam profile and the extreme ultraviolet energy distribution by the analysis module.

[0100] In some embodiments, adjusting the radiation source to enhance the extreme ultraviolet radiation according to the analysis data comprises adjusting the laser beam profile according to the analysis data by the laser alignment unit.

[0101] In some embodiments, adjusting the radiation source to enhance the extreme ultraviolet radiation according to the analysis data comprises adjusting the delivery of the target material droplets according to the analysis data by the target position control unit.

[0102] In some embodiments, adjusting the radiation source to enhance the extreme ultraviolet radiation according to the analysis data comprises adjusting the generation of laser pulses from the laser device according to the analysis data by the laser pulse delay adjustment unit.

[0103] In some embodiments, adjusting the radiation source to enhance the extreme ultraviolet radiation according to the analysis data comprises adjusting a container parameter by the container control unit, and wherein the container parameter comprises one of a container pressure, a container gas flow rate, and a container temperature.

[0104] In another example aspect, the present disclosure provides an extreme ultraviolet (EUV) lithography system. The EUV system includes: a radiation source for generating EUV radiation, wherein the radiation source includes a laser source, a target material droplet generator, and an EUV collector configured in a vessel; a mask stage configured to secure an EUV mask; a wafer stage configured to secure a semiconductor wafer; an optical module designed to direct the EUV radiation from the radiation source in a lithography exposure process to image an IC pattern defined on the EUV mask to the semiconductor wafer; and an EUV control system integrated with the radiation source. The EUV control system includes: a 3-dimensional diagnostic module (3DDM) designed to collect data of the radiation source in a 3D mode; an analysis module designed to analyze the collected data; and an EUV control module designed to adjust the radiation source. The 3DDM is embedded in the radiation source. The analysis module is coupled with the 3DDM and the EUV control module. The EUV control module is coupled with the analysis module and the radiation source.

[0105] In some embodiments, the 3-dimensional diagnostic module includes: a laser monitor for monitoring a laser beam from the laser source; a plasma monitor for monitoring a plasma generated by the laser beam; and an EUV monitor for monitoring an extreme ultraviolet radiation generated from the plasma.

[0106] In some embodiments, the 3-dimensional diagnostic module further includes a contamination monitor for monitoring a contamination from a target material droplet delivered by the target material droplet generator.

[0107] In some embodiments, the analysis module includes: a correlation analysis unit for analyzing a correlation between a laser beam profile of the laser beam and an EUV radiation energy of the EUV radiation; a modeling unit for extracting effect data from the collected data; and a machine learning unit for extracting an effective laser beam profile from the correlated EUV radiation.

[0108] In some embodiments, the control module includes: a laser alignment unit having a mechanism for adjusting the laser beam profile of the laser beam according to an analysis result from the analysis module; a target position control unit having a mechanism for adjusting a delivery of the target material droplet delivered by the target material droplet generator; a laser pulse delay adjustment unit having a mechanism for controlling a generation of a laser pulse from the laser source to synchronize the laser pulse with the target material droplet; and a vessel control unit having a mechanism for adjusting at least one of a vessel pressure, a vessel flow rate, and a vessel temperature of the vessel.

[0109] In yet another example aspect, the present disclosure provides a method for an extreme ultraviolet (EUV) lithography system, the EUV lithography system including a radiation source having a laser device and a laser-produced plasma mechanism for generating EUV radiation. The method includes: collecting 3-dimensional (3D) data of the radiation source, the 3D data including a laser beam profile and an EUV energy of the EUV radiation; performing an analysis on the laser beam profile and the EUV energy to obtain correlation data; and adjusting the radiation source according to the correlation data to enhance the EUV radiation.

[0110] In some embodiments, the method for the EUV lithography system further includes: performing an EUV lithography exposure process on a semiconductor substrate using the EUV lithography system with the adjusted radiation source; performing a development process on the semiconductor substrate after the performing of the EUV lithography exposure process, thereby forming a patterned photoresist layer on the semiconductor substrate; and performing a fabrication process on the semiconductor substrate through openings of the patterned photoresist layer.

[0111] In some embodiments, the EUV lithography system includes an EUV lithography apparatus, the EUV lithography apparatus further including the radiation source; the EUV lithography system includes an EUV control system integrated with the EUV lithography apparatus; and the EUV control system includes a monitoring module, an analysis module, and a control module, wherein the monitoring module is embedded in the radiation source.

[0112] In some embodiments, the monitoring module includes a laser monitor, a plasma monitor, and an EUV monitor; the analysis module includes a correlation analysis unit, a modeling unit, and a machine learning unit; the control module includes a laser alignment unit, a target position control unit, a laser pulse delay adjustment unit, and a vessel control unit; the collecting 3-dimensional (3D) data includes collecting data of the laser beam profile by the laser monitor and collecting data of the EUV energy of the EUV radiation by the EUV monitor; the performing an analysis on the laser beam profile and the EUV energy includes identifying a correlation between the laser beam profile and the EUV energy of the EUV radiation; and the adjusting the radiation source according to the correlation data includes adjusting the laser beam profile by the laser alignment unit.

[0113] The foregoing summary of features of several embodiments has been presented for the purposes of illustration and description. It is based on the recognition that those skilled in the art can readily adapt the disclosure to various processes and structures for the implementation of the same or similar purposes and / or to achieve the same or similar results. It is also recognized that such equivalent structures do not depart from the spirit and scope of the disclosure, and that changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the disclosure.

Claims

1. A method for an extreme ultraviolet (EUV) lithography system, the EUV lithography system comprising a radiation source having a laser device, the laser device being configured with a mechanism for generating EUV radiation, the method comprising: The laser beam profile from the laser device is collected in 3D mode; The extreme ultraviolet energy distribution of the extreme ultraviolet radiation generated by the laser beam is collected in the 3D mode; The laser beam profile and the extreme ultraviolet energy distribution are analyzed to obtain analytical data. as well as The radiation source is adjusted based on the analytical data to enhance the extreme ultraviolet radiation.

2. The method according to claim 1, further comprising: The extreme ultraviolet lithography system with the adjusted radiation source is used to perform extreme ultraviolet lithography exposure on a semiconductor substrate.

3. The method according to claim 2, further comprising: After the extreme ultraviolet lithography exposure process is performed, a development process is performed on the semiconductor substrate to form a patterned photoresist layer on the semiconductor substrate; as well as The semiconductor substrate is fabricated through openings in the patterned photoresist layer.

4. The method according to claim 3, wherein, The manufacturing process includes one of etching and ion implantation.

5. The method according to claim 1, wherein, The extreme ultraviolet lithography system includes an extreme ultraviolet lithography apparatus, and the extreme ultraviolet lithography apparatus further includes the radiation source; The extreme ultraviolet (EUV) lithography system includes an EUV control system integrated with the EUV lithography apparatus; and The extreme ultraviolet control system includes a monitoring module, an analysis module, and a control module, wherein the monitoring module is embedded in the radiation source.

6. The method according to claim 5, wherein, The monitoring module includes a laser monitor, a plasma monitor, and an extreme ultraviolet monitor; The analysis module includes a correlation analysis unit, a modeling unit, and a machine learning unit; and The control module includes a laser alignment unit, a target position control unit, a laser pulse delay adjustment unit, and a container control unit.

7. The method according to claim 6, wherein, The process of collecting the laser beam profile from the laser device in a 3D mode includes collecting the laser beam profile by means of the laser monitor. The collection of the extreme ultraviolet (EUV) energy distribution of the UV radiation generated by the laser beam in the 3D mode includes collecting the EUV energy distribution of the UV radiation through the EUV monitor; and The analysis of the laser beam profile and the extreme ultraviolet energy distribution includes performing the analysis on the laser beam profile and the extreme ultraviolet energy distribution through the analysis module.

8. The method according to claim 6, wherein, The step of adjusting the radiation source to enhance the extreme ultraviolet radiation based on the analysis data includes adjusting the laser beam profile by means of the laser alignment unit based on the analysis data.

9. The method according to claim 6, wherein, The step of adjusting the radiation source to enhance the extreme ultraviolet radiation based on the analysis data includes adjusting the delivery of target material droplets by the target position control unit based on the analysis data.

10. The method according to claim 6, wherein, The step of adjusting the radiation source to enhance the extreme ultraviolet radiation based on the analysis data includes adjusting the generation of laser pulses from the laser device by the laser pulse delay adjustment unit based on the analysis data.

11. The method according to claim 6, wherein, The step of adjusting the radiation source to enhance the extreme ultraviolet radiation based on the analysis data includes adjusting container parameters through the container control unit, wherein the container parameters include one of container pressure, container gas flow rate, and container temperature.

12. An extreme ultraviolet lithography system, comprising: A radiation source for generating extreme ultraviolet radiation, wherein the radiation source includes a laser source, a target material droplet generator, and an extreme ultraviolet collector configured in a container; The mask stage is configured to fix an extreme ultraviolet mask. A wafer stage, configured to hold semiconductor wafers; An optical module is designed to guide extreme ultraviolet radiation from the radiation source during a photolithography process to image an IC pattern defined on the extreme ultraviolet mask onto the semiconductor wafer; and An extreme ultraviolet (EUV) control system, integrated with the radiation source, includes a 3D diagnostic module designed to collect data from the radiation source in a 3D mode, an analysis module designed to analyze the collected data, and an EUV control module designed to adjust the radiation source. The 3D diagnostic module is embedded in the radiation source. The analysis module is coupled to both the 3D diagnostic module and the EUV control module. Furthermore, the EUV control module is coupled to both the analysis module and the radiation source. The analysis module includes: A correlation analysis unit is used to analyze the correlation between the laser beam profile of the laser source and the extreme ultraviolet radiation energy. A modeling unit is used to extract effect data from the collected data; and A machine learning unit is used to extract an effective laser beam profile based on the relevant extreme ultraviolet radiation.

13. The extreme ultraviolet lithography system according to claim 12, wherein, The 3D diagnostic module includes: A laser monitor for monitoring the laser beam from the laser source; A plasma monitor for monitoring the plasma generated by the laser beam; and An extreme ultraviolet (EUV) monitor is used to monitor the EUV radiation generated from the plasma.

14. The extreme ultraviolet lithography system according to claim 13, wherein, The 3D diagnostic module also includes a contamination monitor for monitoring contamination from target material droplets delivered by the target material droplet generator.

15. The extreme ultraviolet lithography system according to claim 13, further comprising: The database is designed to store the laser beam profile of the laser beam.

16. The extreme ultraviolet lithography system according to claim 13, wherein, The control module includes: The laser alignment unit has a mechanism for adjusting the laser beam profile based on the analysis results from the analysis module; The target position control unit has a mechanism for regulating the delivery of target material droplets delivered by the target material droplet generator; A laser pulse delay adjustment unit includes a mechanism for controlling the generation of laser pulses from the laser source to synchronize the laser pulses with the target material droplets; and The container control unit has a mechanism for adjusting at least one of the container pressure, container flow rate, and container temperature of the container.

17. A method for an extreme ultraviolet (EUV) lithography system, the EUV lithography system comprising a radiation source having a laser device and a laser-generating plasma mechanism for generating EUV radiation, the method comprising: Collect 3D data of the radiation source, including the laser beam profile and the extreme ultraviolet energy of the extreme ultraviolet radiation; The laser beam profile and the extreme ultraviolet energy were analyzed to obtain correlation data; as well as The radiation source is adjusted according to the correlation data to enhance the extreme ultraviolet radiation.

18. The method of claim 17, further comprising: The extreme ultraviolet lithography system with the adjusted radiation source is used to perform extreme ultraviolet lithography exposure process on semiconductor substrates; After the extreme ultraviolet lithography exposure process is performed, a development process is performed on the semiconductor substrate to form a patterned photoresist layer on the semiconductor substrate; as well as The semiconductor substrate is fabricated through openings in the patterned photoresist layer.

19. The method of claim 17, wherein, The extreme ultraviolet lithography system includes an extreme ultraviolet lithography apparatus, and the extreme ultraviolet lithography apparatus further includes the radiation source; The extreme ultraviolet (EUV) lithography system includes an EUV control system integrated with the EUV lithography apparatus; and The extreme ultraviolet control system includes a monitoring module, an analysis module, and a control module, wherein the monitoring module is embedded in the radiation source.

20. The method according to claim 19, wherein, The monitoring module includes a laser monitor, a plasma monitor, and an extreme ultraviolet monitor; The analysis module includes a correlation analysis unit, a modeling unit, and a machine learning unit; The control module includes a laser alignment unit, a target position control unit, a laser pulse delay adjustment unit, and a container control unit; The collection of the 3D data of the radiation source includes data on the laser beam profile collected by the laser monitor and data on the extreme ultraviolet energy of the extreme ultraviolet radiation collected by the extreme ultraviolet monitor. The analysis of the laser beam profile and the extreme ultraviolet energy includes identifying the correlation between the laser beam profile and the extreme ultraviolet energy of the extreme ultraviolet radiation; and Adjusting the radiation source based on the correlation data includes adjusting the laser beam profile via the laser alignment unit.

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