High numerical aperture extreme ultraviolet lithography system and lithography method

Abstract

The invention provides a high numerical aperture extreme ultraviolet lithography system and a lithography method. According to the system, through a passband confinement structure of double-pupil fractional exposure, wafer exposure dose is fused by cosine weight, and a physical dissipation device is superposed to selectively couple a pupil plane odd symmetry mode, so that spurious energy is prevented from being recharged into an imaging channel; and a dual-channel dark port interference structure is introduced to monitor and correct wafer inclination and defocus disturbance in real time, and meanwhile, a mask adopts a multi-layer phase flat reflection stack and a high-infrared-emissivity protection film to ensure that the phase of a light beam is stable. A wavefront phase monitoring structure is integrated in a wafer scribing area, image pupil phase pickup and aberration parameter collection in the exposure process are achieved, the relation between the critical dimension, the dosage and the focal length deviation of each exposure field is calibrated through a unified edge rule, the consistency of an actual exposure phase and three-dimensional electromagnetic simulation is used as an imaging constraint, only second-order internal disturbance is controlled and compensated, and the imaging precision is greatly improved. And higher-order disturbance is recorded as a residual error, so that the imaging resolution and stability of high NA extreme ultraviolet lithography are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor lithography equipment, and particularly relates to a high numerical aperture extreme ultraviolet lithography system and a lithography method, which aims to improve the imaging resolution, stability and process consistency of high numerical aperture extreme ultraviolet lithography. BACKGROUND

[0002] With the continuous reduction of integrated circuit feature size, extreme ultraviolet lithography technology has been introduced into chip manufacturing. However, in order to further improve the resolution capability, the numerical aperture (NA) of the lithography system is also continuously increasing. From the current mainstream extreme ultraviolet lithography machine with a numerical aperture of about 0.33 to a high numerical aperture (such as 0.55 or even higher), a series of technical challenges will be brought. First, the high numerical aperture leads to a sharp decrease in the depth of field (DOF), only tens of nanometers, so that the control accuracy of the focal plane is extremely high; a slight focus deviation or wafer tilt can cause the pattern resolution to decrease and the line width error to increase. The existing extreme ultraviolet lithography machine usually controls the focal plane position through wafer leveling before exposure and fixed off-line correction, but if disturbances such as platform vibration and thermal drift occur during the exposure process, the traditional system is difficult to perceive and correct in time, which is easy to cause image blur or ghosting.

[0003] Secondly, the problem of stray light and odd-symmetry optical mode coupling is easy to occur in the high numerical aperture lithography light path. Part of the light may form a non-imaging odd-symmetry mode after multiple reflections between the mirror surfaces of the projection objective. Without special processing, these energies can return and interfere with the normal imaging beam, resulting in a decrease in image quality (such as producing flare, reducing contrast, etc.). The current lithography system usually uses diaphragm limiting, light extinction coating and other means to reduce interference, but the new type of optical mode coupling effect under high numerical aperture conditions still lacks an effective real-time suppression mechanism.

[0004] Thirdly, the multi-layer structure of the extreme ultraviolet mask will introduce obvious "three-dimensional effect" under high numerical aperture oblique incidence conditions. The mask is composed of about 40-50 pairs of alternating Mo / Si thin films to form a reflective multilayer, and has an absorption pattern on top, which has a thickness that changes the phase and amplitude of the reflected light with the incident angle and polarization state, causing additional phase difference and focal shift at different positions on the image plane. Under high numerical aperture, the incident angle is larger, and the shadow effect and phase distortion of the mask are more serious, resulting in an increase in pattern transfer error. The existing technology alleviates the mask 3D effect by optimizing the illumination setting (such as using an asymmetric magnification optical system) or compensating for the mask pattern, but it is still insufficient to ensure the phase stability of high numerical aperture imaging. In addition, the extreme ultraviolet mask will absorb energy and heat during exposure, causing thermal deformation and further disturbing the phase of the mask surface. Although there are schemes to strengthen heat dissipation by adding a protective film in front of the mask or improving the mask material, the thermal stability of the mask under high numerical aperture conditions is still a major challenge.

[0005] Fourthly, as the lithography resolution is improved, the fine pattern formed on the wafer is extremely sensitive to any optical aberration. The conventional exposure apparatus generally only measures the aberration of the projection objective lens by using an interferometer at the factory calibration or regular maintenance, or obtains the depth of focus and dose margin by the method of trial exposure (for example, analyzes the curve of line width changing with focus and dose). In batch production, the aberration can gradually change due to temperature drift, mechanical stress, etc., but there is currently no means to directly obtain and correct the optical aberration in each exposure process, which makes the aberration correction lagging. For a high numerical aperture system, this lagging can cause cumulative errors, affecting the reproducible accuracy of multiple exposures.

[0006] In addition, the subtle differences in conditions between different exposure fields (such as field edge light intensity, scanning motion error, etc.) can cause the critical dimension (CD) of the pattern in each exposure field to deviate. Traditionally, in order to ensure the consistency of the pattern across the wafer, a large process margin needs to be reserved or a correction step needs to be added after exposure, which increases the process complexity and cannot ensure the consistency of the performance of each exposure field from the source.

[0007] Finally, the extreme ultraviolet light source often accompanies a certain proportion of non-13.5 nm wavelength impurity light (out-of-band light), such as about 40 nm of third harmonic of fundamental wave 13.5 nm, etc. If these out-of-band lights enter the exposure process, they will change the reaction of the photoresist, causing problems such as an increase in line edge roughness (LER). The existing extreme ultraviolet system generally installs a filter assembly in the light source or the projection light path to suppress the out-of-band components, but the filter will waste part of the effective light intensity, and it is not clear how much the residual out-of-band components will affect the final pattern size accuracy. If the requirement for spectral purity is excessively improved, it can lead to more complex system design, lower output power, and higher cost;

[0008] Therefore, a high numerical aperture extreme ultraviolet lithography system and a lithography method are provided to solve the problems raised in the background art. SUMMARY

[0009] In order to overcome the above-mentioned defects of the prior art, embodiments of the present application provide a high numerical aperture extreme ultraviolet lithography system and a lithography method to solve the problems raised in the background art.

[0010] To achieve the above-mentioned purposes, the present application aims to provide an improved high numerical aperture extreme ultraviolet lithography system and a lithography method to solve the focusing, imaging stability and consistency problems in the above-mentioned high numerical aperture extreme ultraviolet lithography.

[0011] Providing a passband limiting structure for dual-pupil fraction exposure: the exposure to the same pattern area is divided into two times through different pupil channels, and each partial exposure is allocated dose according to the preset cosine function weight, and the total exposure dose is fused and accumulated on the wafer surface, so that the weight sum is 1. The dual-exposure scheme expands the effective imaging pupil band range, and avoids the decline of image quality under the limit of single exposure by smoothing the weight distribution.

[0012] Preferably, introducing a physically dissipating device with odd symmetry mode selective coupling in the projection pupil plane: the odd symmetry light field mode not used for imaging in the image pupil plane is directionally coupled, introduced and dissipated, avoiding the backflow of this part of energy into the imaging light path to cause interference. The device can be a special absorption structure or a wave-trap element arranged at the image pupil plane, which only couples the stray mode with a specific symmetry and converts it into heat energy to dissipate.

[0013] Preferably, configuring a dual-channel dark port interference structure for real-time detection and correction of tilt and defocus disturbance: the actual position of the wafer is compared with the reference beam through a set of interference light paths. When the wafer is slightly tilted or the focal plane is shifted, a bright-dark signal difference is generated at the dark port of the interferometer. The tilt angle and focal length error are measured in real time through the differential signal, and the wafer table or the projection optical element is driven for closed-loop correction to ensure that the wafer surface strictly adheres to the focal plane during each exposure.

[0014] Preferably, improving the extreme ultraviolet mask structure: the mask adopts a multi-layer phase flattening reflection stack design, and a high infrared emissivity protective film is added on the surface of the mask. On the one hand, the multi-layer stack of the mask can optimize the reflection phase at each incident angle to be consistent, reducing the phase distortion caused by the 3D effect of the mask; on the other hand, the high infrared emissivity protective film helps the mask to quickly radiate the absorbed heat energy, reducing the temperature rise and thermal deformation, thereby ensuring the phase stability of the mask reflection wavefront during exposure.

[0015] Preferably, a phase beacon structure is arranged on the wafer scribing area: a specific optical structure (such as a micro-mirror or a diffraction grating) is arranged in the scribing area of each exposure field of the wafer. When the exposure light irradiates the area, a known mode of optical echo signal is returned to the projection optical system. By detecting the echo signal, the information of the image pupil plane wavefront phase corresponding to the exposure instant can be obtained, which is equivalent to in-situ wavefront detection at each exposure field, providing a reference for aberration monitoring and correction.

[0016] Preferably, a sub-pupil orthogonal perturbation probe structure is arranged: several miniature sensing probes or actuators are distributed within the image pupil plane of the projection lens to introduce and sense small-amplitude, mutually orthogonal and independent wavefront perturbations. For example, known perturbations can be applied to the basic orthogonal modes of aberrations (such as Zernike polynomial modes) and their effects on imaging or echo signals can be observed, thereby inverting the actual values ​​of each aberration term in the current system. This structure enables rapid acquisition of key aberration parameters (such as astigmatism, coma, etc.) within each exposure cycle, laying the foundation for dynamic aberration compensation.

[0017] Preferably, a unified edge rule calibration is implemented: by acquiring the relationship curves (Bossung curves) of linewidth versus focal length and dose at different exposure fields, a quadratic polynomial is used for fitting, the quadratic coefficients of each exposure field are extracted, and the scanning exposure parameters are adjusted to make these quadratic coefficients of all exposure fields tend to be consistent. In other words, this invention ensures that the critical size of each exposure field has the same sensitivity to focal length and dose deviations, thereby unifying the imaging characteristics of each field and reducing pattern differences across the entire wafer.

[0018] Preferably, a record-based counter-evidence experimental criterion is introduced: This invention proposes to introduce only the third harmonic component of the light source's spectral tail in a dedicated test area for comparative exposure, recording its impact on image quality. Experimental results show that although adding spectral tail light of approximately 40 nm wavelength causes an increase in the photoresist line edge roughness (LER), the edge fitting curve after unified calibration in this invention remains essentially unchanged. This result verifies that spectral tail stray light mainly affects pattern roughness rather than dimensional deviation. Therefore, the control strategy of this invention does not use this harmonic component as a criterion for affecting pattern size; only its impact on roughness needs to be considered in the process.

[0019] Preferably, an imaging equivalence constraint is established to ensure consistency between the actual exposure phase and the three-dimensional electromagnetic simulation: A detailed three-dimensional electromagnetic field simulation of the lithography system is performed to obtain the ideal wavefront phase distribution, which is then compared in real-time with the wavefront phase measurement results during the actual exposure process. This invention uses the consistency between the two as one of the constraints on imaging quality. When a significant deviation between the actual wavefront and the simulation expectation is detected, the system will issue a signal indicating the need for recalibration or maintenance. This ensures that all physical factors affecting imaging are within the model's expected range, improving the predictability and reliability of the imaging results.

[0020] Preferably, the control system is limited to active compensation for second-order disturbances, while higher-order disturbances are recorded and archived: The control strategy of this invention only performs real-time active compensation for second-order and lower-order aberration disturbances (such as tilt, defocus, astigmatism, and other major items), while recording higher-order disturbance components as residuals and not directly correcting them during exposure. This trade-off is based on the fact that higher-order aberrations have a relatively small impact on image quality and are difficult to correct. By recording and analyzing them, they can be used for subsequent maintenance and optimization, while avoiding the noise and instability that may be introduced by overly complex closed-loop control, thereby simplifying system design and improving control robustness.

[0021] In summary, through the above technical solutions, this invention realizes a system and method that can achieve both ultra-high resolution and stable process control in high numerical aperture extreme ultraviolet lithography.

[0022] Compared with the prior art, the present invention achieves significant beneficial effects in the following aspects through the above design:

[0023] Higher imaging resolution and process margin: Dual-pupil fractional exposure expands the imaging spectrum, effectively improving the resolution limit. Simultaneously, dose-cosine weighted fusion reduces the depth-of-focus requirement for a single exposure, expanding both depth of field and exposure tolerance. Compared to single-exposure methods, this invention provides a larger focal length and dose process window while maintaining the same resolution.

[0024] More stable optical imaging quality: The odd-symmetric mode dissipation design of the pupil plane actively eliminates stray mode interference unique to high numerical aperture systems, improving the purity of the light intensity distribution on the image plane; combined with a high infrared emissivity mask protection film to reduce thermally induced phase drift, the wavefront quality is more stable and controllable throughout the exposure process.

[0025] Real-time nanometer-level focusing and correction capability: Dual-channel dark port interferometry enables millisecond-level detection and correction of wafer tilt and focus shift, which can control focus error at the nanometer level. This is significantly better than the accuracy of traditional post-exposure correction and offline alignment, and reduces image blurring and interlayer shift caused by vibration or thermal drift.

[0026] Built-in wavefront monitoring and aberration compensation: The combination of on-chip phase beacons and sub-pupil perturbation probes is equivalent to introducing a wavefront sensor inside the lithography system, which can acquire the current aberration status of the projection optics at any time, enabling monitoring while exposure is being performed. This online wavefront monitoring capability ensures the imaging consistency of the high numerical aperture system during long-term operation without the need for frequent downtime for inspection.

[0027] Consistent pattern size control across the entire wafer: By using a unified edge rule for calibration, the response of each exposure field to changes in focal length and dose tends to be consistent, significantly improving the uniformity of CD across the entire wafer. Compared to traditional methods that require a large margin to cover inter-field differences, this invention can actively calibrate inter-field differences, reduce product linewidth dispersion, and improve yield.

[0028] Simplified light source purity requirements: Contrary to experimental evidence, weak spectral tail harmonics have negligible impact on size control, therefore this invention does not incorporate them into the control loop. This allows the system to avoid paying an excessive price for extreme spectral purity, providing greater margin in light source and optical design, while the increase in random roughness caused by spectral tails can be addressed within an acceptable range through process optimization.

[0029] High reliability of imaging results: By comparing the actual exposure wavefront with the simulation model, this invention can promptly detect any abnormal imaging deviations and issue warnings, thereby ensuring that the image quality is always within the expected range. This model constraint makes the introduction of new processes more confident and facilitates the evaluation of the effects of different parameters during process optimization.

[0030] Optimized control robustness: A strategy of providing rapid feedback only for major aberrations, while leaving higher-order disturbances to be recorded and analyzed, results in a simpler and more stable control system structure. This reduces the bandwidth requirements and noise amplification risk of the closed-loop system, avoiding unnecessary complexity while maintaining high-precision control, and is beneficial for the long-term reliable operation and maintenance of the equipment. Attached Figure Description

[0031] Figure 1 This is a block diagram of the overall structure of the high numerical aperture extreme ultraviolet lithography system of the present invention;

[0032] Figure 2 This is a schematic diagram of the photolithography method of the present invention;

[0033] Figure 3 This is a schematic diagram of the dual-pupil sequential exposure and cosine weighted fusion of the present invention;

[0034] Figure 4 This is a structural diagram of the selective dissipation device for the odd-symmetric mode of the pupil plane of the present invention;

[0035] Figure 5 This is a structural diagram of the dual-channel dark port interferometry method of the present invention;

[0036] Figure 6 This is a schematic diagram of the on-chip phase beacon and pupil phase pickup of the present invention;

[0037] Figure 7 This is a schematic diagram of the unified edge rule calibration of the present invention;

[0038] Figure 8This is a schematic diagram of the higher-order residual record of the present invention;

[0039] Figure 9 This is a schematic diagram of the mask structure of the present invention; Detailed Implementation

[0040] The following will refer to the appendices in the embodiments of the present invention. Figures 1-9 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] The high numerical aperture extreme ultraviolet lithography system and method of the present invention will be further described below with reference to specific embodiments.

[0043] The overall structure of the lithography system of this invention includes: an extreme ultraviolet (EUV) light source and illumination optical system, a mask stage and mask, a projection lens group, a wafer stage, and corresponding control and monitoring units, similar to the basic architecture of existing EUV lithography equipment. However, based on the above, the system integrates several novel components and control methods to achieve performance improvements at high numerical apertures. For example, the illumination optical system is equipped with a dual-pupil sequential exposure device, which can switch between two different pupil filling modes through a programmable aperture or a multi-channel illumination module, performing two sequential exposures on the same exposure field. Specifically, during the first exposure, the system uses a first pupil transmission function (e.g., partial pupil illumination biased in a specific direction) to illuminate the mask pattern, imparting a cosine component of the dose to the wafer exposure; then the system switches to the second pupil transmission mode for the second exposure, imparting a compensated dose component. The two exposures are positioned and aligned with the same area, and the respective doses are precisely set by controlling the exposure time or intensity, so that the total dose after superposition reaches the design value and remains uniform. This dual-pupil multi-exposure method expands the effective imaging spectrum range on the one hand, and reduces the extreme requirements of single exposure on depth of focus and image quality on the other hand, which is equivalent to improving the process margin.

[0044] At the image pupil plane of the projection lens, this invention introduces an odd-symmetric mode dissipation device. For example, a specially designed ring-shaped absorption structure is placed at the image pupil, whose transfer function selectively couples to odd-symmetric optical field modes. The even-symmetric light distribution normally used for imaging passes through largely unaffected, while stray light modes with odd-symmetric distributions that cannot be imaged are captured by the absorption ring, and their energy is dissipated as heat. In this way, these stray modes are prevented from propagating again in the optical path or being reflected back to the objective lens, preventing them from entering the image plane and causing noise or contrast loss. This physical dissipation device requires no active control and functions continuously as a passive element, effectively improving the imaging purity of high numerical aperture systems.

[0045] For wafer alignment and focusing control, this invention integrates a dual-channel dark-port interferometry structure into the system. The implementation involves one alignment reference beam illuminating the wafer surface (or a reference plane on the wafer stage), while another reference beam travels directly to the interferometer detector via a fixed optical path. The two beams are superimposed in the interferometer, with one output configured as a dark field (in ideal alignment, the two beams are destructively phased by π). When the wafer experiences a slight tilt or height (focal length) shift, a phase difference occurs between the reference and reflected beams, generating a light signal of a certain intensity at the original dark-port location. By detecting the intensity of this signal and the fringe phase change, the wafer tilt angle and defocusing error can be calculated. This measurement is performed continuously in real-time. The system controller adjusts the three degrees of freedom of the wafer stage (e.g., pitch angle and Z-axis height) in real-time based on the interferometric signal, or links the focusing mechanism of the projection lens for closed-loop correction. Thus, during each exposure frame, the actual focal plane of the wafer surface always precisely coincides with the projected image plane, allowing for immediate detection and correction even in the event of environmental vibrations or thermal drift. Experimental simulations show that this real-time differential interferometric focusing system can control focal plane error at the nanometer level, significantly improving the focusing stability of high numerical aperture exposures.

[0046] In terms of mask technology, this invention employs a specially designed multilayer reflective stack and protective film combination to improve phase stability and thermal reliability. The multilayer film system of the mask optimizes the thickness and material of each layer to minimize the phase difference of reflected light from each diffraction order within the main incident angle range, achieving so-called "phase flattening." For example, a non-periodic multilayer film design can be used to compensate for the reflection phases of the mask at different angles, thereby reducing the focus shift caused by the 3D effect of traditional masks. Furthermore, a transparent protective film with high infrared emissivity (e.g., a specially formulated silica-based material) is applied to the top layer of the mask. This film is almost transparent to extreme ultraviolet light at a wavelength of 13.5 nm, not affecting imaging, but has high emissivity in the longer infrared band, allowing the heat generated by the mask due to light heating to dissipate rapidly in the form of radiation. Through these two improvements, the wavefront phase of the mask remains stable during high numerical aperture exposure, reducing image shift caused by aberrations and thermal deformation introduced by the mask, and significantly improving the accuracy of pattern transfer.

[0047] Furthermore, this invention incorporates an on-chip phase beacon structure within the dicing area of ​​each exposure field on the wafer to enable real-time wavefront monitoring. Specifically, a small area can be reserved in the dicing path to deposit a reflective grating or mirror. This structure does not participate in circuit pattern imaging but is illuminated during exposure and reflects a portion of the light back to the projection lens. Because its structural period or reflection characteristics are known, the returned light carries the phase information of the wavefront of the current exposure optical system. The system employs detectors or sensors on the pupil or conjugate plane of the projection lens to receive the echo signal from this phase beacon and extract the wavefront phase through interferometry or other optical analysis methods. This effectively performs wavefront detection for each exposure field at the moment of exposure. Combining this measurement result with existing aberration models in the system, wavefront errors caused by optical component deformation or environmental changes can be promptly detected and corrected, ensuring that the imaging quality of each field meets requirements.

[0048] Simultaneously, a sub-pupil orthogonal perturbation probe structure is integrated into the projection optics system for comprehensive aberration monitoring and correction. This structure can be implemented by placing small dynamic phase modulation elements or micro-optical sensor arrays on the pupil plane. For example, several miniature variable phase plates are located in different quadrants of the pupil plane, and each phase plate can superimpose a small phase shift perturbation on the wavefront passing through its sub-pupil region when needed. By comparing the imaging characteristics before and after the perturbation (e.g., changes in echoes from on-chip beacons or other focal plane detections), the system can calculate the corresponding aberration component values. Each sub-pupil perturbation is designed to be orthogonal and independent (e.g., corresponding to aberration modes of a set of orthogonal basis functions), thus allowing the simultaneous or sequential solving of the real-time changes of multiple major aberration parameters (e.g., X-direction astigmatism, Y-direction astigmatism, first-order coma, etc.). This orthogonal probe method is equivalent to a built-in wavefront sensor, allowing the system to acquire optical aberration data without interrupting exposure and providing the results to the control unit for further calibration.

[0049] By utilizing the on-chip phase beacon and sub-pupil probe structures described above, the system control unit of this invention can accurately evaluate and adjust the optical state of each exposure field. Specifically, after completing the exposure of the entire wafer, the system collects critical dimension (CD) measurements and corresponding exposure parameters (dose, focal length settings, etc.) for each exposure field, and establishes a CD-focal length / dose curve model for each field through data analysis. Using the unified edge rule, these curves are fitted and compared using a quadratic polynomial. If differences are found in the quadratic coefficients of some fields, the control unit can adjust the exposure dose or focal plane setting of the corresponding field (e.g., slightly change the focus compensation amount for that field) to make the CD sensitivity to focal length and dose changes of all exposure fields more consistent. This calibration process can be completed during the initial process debugging stage and verified periodically during production. When the unified edge rule is satisfied, the pattern size distribution across the entire wafer will be more uniform, greatly reducing product yield fluctuations caused by differences between equipment fields.

[0050] It is worth mentioning that this invention further verifies the effectiveness of the system control strategy through a special comparative experiment. In the experiment, controlled extreme ultraviolet extraspectral third harmonic light (approximately 40 nm wavelength) was introduced into a specific area of ​​the test wafer to simulate the effect of the spectral tail component on pattern imaging under the most extreme conditions. The test results show that after introducing a small amount of spectral tail light, the line edge roughness (LER) of the exposed pattern increased, but after uniform edge calibration, the critical dimensions and edge positions of each test structure did not shift significantly and remained basically consistent with those without the introduction of the spectral tail. This counter-evidence experiment demonstrates that the higher harmonics of the light source spectral tail mainly affect the pattern coarseness of random noise types, without violating the size control law established by this invention. Therefore, in actual operation, the system of this invention does not require additional complex compensation for weak extraspectral stray light; it only needs to ensure that its content does not cause unacceptable roughness, thereby simplifying the system design.

[0051] Finally, the control strategy of this invention focuses on the active correction of low-order disturbances, while adopting a monitoring and recording approach rather than immediate correction for high-order disturbances. In practice, the system typically corrects the first few aberrations that have the greatest impact on imaging in real time (e.g., 0th-order intensity, 1st-order tilt, 2nd-order defocus and astigmatism). These low-order errors can be quickly measured through interferometry and wavefront sensing and corrected promptly by actuators (such as wafer stage positioners, projection lens focusing mechanisms, etc.). Aberrations of the third order and above, such as coma and spherical aberration, change slowly and have a relatively small impact on a single exposure. Therefore, the system does not attempt to dynamically eliminate them in each exposure, but rather records their changes using the aforementioned sensing methods. If these high-order errors accumulate to a certain level over time, the system will perform a one-time correction during maintenance by readjusting optical components or offline calibration. This control trade-off avoids introducing too many high-order corrections into the real-time control loop, thereby avoiding the complexity of the control system and potential instability factors, ensuring reliable and efficient system operation.

[0052] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0053] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0054] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high numerical aperture extreme ultraviolet lithography system comprising an illumination optical system, a mask, a projection objective and a wafer stage, characterized in that, The system comprises: A dual-pupil split-exposure passband limiting structure, which fuses the doses of two exposures according to cosine weights on a wafer surface, so that the total dose weight sum is 1; A pupil surface odd-symmetry mode selective coupling physical dissipation device, which is used for dissipating the energy of an odd-symmetry non-imaging mode to prevent the energy from returning to an imaging light path; A dual-channel dark port interference measurement device, which is used for real-time differential detection of tilt and defocus disturbances of the wafer and outputs a control signal to close-loop correct a position and posture of the wafer table; The mask has a multi-layer phase flat reflective stack and a high infrared emissivity protective film to ensure stability of an imaging phase of an exposure light beam; The wafer carried on the wafer table is provided with an on-chip phase beacon structure in a scribing area, which is used for generating a wavefront phase echo signal during an exposure process and picking up an image pupil phase by a system; A sub-pupil orthogonal perturbation probe structure is arranged on an image pupil surface of the projection objective, which is used for collecting optical aberration parameters during an exposure period.

2. A high numerical aperture extreme ultraviolet lithography system according to claim 1, wherein, A control unit of the system adopts a unified edge rule to perform quadratic fitting calibration on relationships between critical dimensions of each exposure field, exposure doses and focus deviation, so that a quadratic term coefficient of the relationships is consistent in all exposure fields, and actual exposure wavefront phases are compared with preset three-dimensional electromagnetic simulation results, and consistency in the comparison is taken as a constraint condition of imaging equivalence.

3. A high numerical aperture extreme ultraviolet lithography system according to claim 1 or 2, wherein, The control unit only performs real-time feedback correction on aberration disturbances of a second order and below, and records disturbances higher than the second order as residuals without taking them as control inputs.

4. A high numerical aperture extreme ultraviolet lithography method, characterized by, The photolithography system of claim 1 is used to perform a photolithography process, comprising the following steps: S1, providing a mask having a multi-layer phase flat reflective stack and a high infrared emissivity protective film, and a wafer having an on-chip phase beacon structure in a scribing area, and mounting the mask and the wafer to a mask table and a wafer table of the photolithography system; S2, performing dual-pupil split-exposure on a target pattern field through an illumination optical system, illuminating the mask through different pupil channels and exposing the same wafer area twice, and allocating doses of each exposure according to a predetermined cosine weight, and superimposing the two exposures to make the wafer area obtain a predetermined total dose; S3, during the exposure process, using a pupil surface odd-symmetry mode selective coupling physical dissipation device to couple out and physically dissipate the energy of an odd-symmetry non-imaging mode in an image pupil surface of a projection objective, so as to avoid the energy returning to the imaging light path to affect exposure imaging; S4, during the exposure process, using a dual-channel dark port interference measurement device to detect tilt and defocus disturbances of the wafer in real time, and controlling a position and posture of the wafer table and / or the projection objective to perform closed-loop correction, so as to keep the wafer focal plane and the imaging plane accurately coincident; S5, during the exposure process, reflecting a part of the exposure light beam by the on-chip phase beacon structure in the scribing area of the wafer to obtain a corresponding image pupil surface wavefront phase picked up by the system, and combining optical aberration change information collected by the sub-pupil orthogonal perturbation probe structure to determine aberration parameters of the current exposure. S6. Repeat steps S2-S5 to complete the graphic transfer of multiple exposure fields. Then, perform a quadratic polynomial fitting analysis on the distribution of the measured values ​​of the key dimensions of each exposure field with the exposure dose and focal length deviation. Adjust the control parameters according to the unified edge rule to keep the quadratic fitting coefficients of each exposure field consistent. S7. Compare and verify the wavefront phase measurement results during the actual exposure process with the pre-established three-dimensional electromagnetic simulation wavefront. When the two are consistent, it is determined that the imaging process meets the equivalence requirements. S8. During the entire photolithography process, active compensation control is performed only for disturbances of second order and below, while disturbances of higher order are recorded and saved as residual information and are not used for control correction.

5. A mask for extreme ultraviolet lithography, characterized in that, It includes a multilayer phase-flat reflective film stack and a high infrared emissivity protective film covering its surface to maintain the phase flatness of the reflected wavefront of the mask and reduce thermal deformation during high numerical aperture extreme ultraviolet lithography exposure.

6. A wafer structure for extreme ultraviolet lithography, wherein the dicing region has an on-chip phase beacon structure, the phase beacon structure being able to reflect a specific optical signal during exposure to provide feedback measurement of the image pupil wavefront phase.

7. A wafer structure for extreme ultraviolet lithography according to claim 6, wherein the on-chip phase beacon structure is a reflective diffraction grating or a mirror structure pre-placed in the dicing area.

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