Non-imaging lithography illumination system for an i-line photolithography machine

Abstract

The application relates to the technical field of photoetching equipment and discloses a non-imaging photoetching illumination system of an i-line photoetching machine, which comprises a light source module that provides an i-line exposure light beam by using an LED light source, a zoom module that adjusts an illumination coherence factor to generate an off-axis illumination pupil, a pupil monitoring module that collects an illumination pupil image, extracts a pupil characteristic value and forms a pupil characteristic time sequence, a homogenization module that performs homogenization shaping on the light beam, a mask surface monitoring module that collects an exposure surface uniformity distribution image, extracts a uniformity index and forms a uniformity characteristic time sequence, an empirical mode decomposition module that decomposes the pupil characteristic time sequence and the uniformity characteristic time sequence, an identification module that identifies intrinsic mode function components with matched center frequencies, a calculation module that calculates an instantaneous phase difference time sequence, a correction loop selection module that selectively activates correction loops of the zoom module and the homogenization module according to the fluctuation range of the instantaneous phase difference, and an online separation and independent correction module that realizes online separation and independent correction of the pupil distribution and the illumination uniformity and improves the stability and process adaptability of photoetching illumination.

Description

Technical Field

[0001] This invention relates to the technical field of lithography equipment and discloses a non-imaging lithography illumination system for an i-line lithography machine. Background Technology

[0002] In the semiconductor integrated circuit manufacturing process, i-line lithography machines are key equipment for micro- and nano-patterning. The performance of their illumination system directly determines the lithography resolution, linewidth uniformity, and process stability. However, existing technologies still have many shortcomings. For example, there is a complex coupling between pupil drift and uniformity degradation, and the root cause is difficult to identify online. Pupil changes caused by mechanical wear or temperature drift will change the beam angle spectrum, thereby affecting the incident light efficiency of the homogenizing module and leading to uniformity degradation. Due to the lack of decoupling methods, adjusting the zoom to improve the pupil will destroy uniformity, and adjusting the homogenizing to improve uniformity will disturb the pupil shape. The loops are coupled and interfere with each other, making it difficult for the system to converge and resulting in low correction efficiency. Traditional methods can only obtain instantaneous feature values ​​or independent time-series monitoring, which cannot reveal the evolution relationship between the two at different time scales and make it difficult to detect and respond to slow drift in a timely manner. Summary of the Invention

[0003] To address the aforementioned technical problems, the main objective of this invention is to provide a non-imaging lithography illumination system for an i-line lithography machine, comprising:

[0004] The light source module uses an LED light source to provide the exposure beam in the i-line exposure band;

[0005] The zoom module changes the illumination coherence factor by adjusting the spacing of the internal lens group, thereby generating a preset off-axis illumination pupil distribution;

[0006] The pupil monitoring module acquires two-dimensional energy distribution images of the illumination pupil and extracts pupil feature values ​​that characterize the pupil morphology from each frame image to form a pupil feature time series.

[0007] The decoupling controller receives the pupil feature time series and the uniformity feature time series, and performs empirical mode decomposition to obtain intrinsic mode function components at different time scales. From the intrinsic mode function components of the pupil feature time series and the intrinsic mode function components of the uniformity feature time series, it identifies the intrinsic mode function components with matching center frequencies, performs Hilbert transform on the intrinsic mode function components with matching center frequencies, calculates the instantaneous phase difference time series, and activates the correction loop for the zoom module and the correction loop for the uniformity module.

[0008] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0009] The pupil monitoring module samples the light beam through a beam splitter and guides the beam to a photodetector array located on the conjugate surface of the pupil;

[0010] If the fluctuation range of the instantaneous phase difference time series is less than the preset phase threshold, it is determined that the uniformity degradation is dominated by pupil drift, and the correction circuit of the zoom module is activated.

[0011] If the fluctuation range of the instantaneous phase difference time series is greater than or equal to the preset phase threshold, it is determined that the uniformity degradation is dominated by the performance drift of the uniform light module, and the correction loop for the uniform light module is activated.

[0012] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0013] The pupil feature value is a quantitative index of the pupil shape selected according to the current illumination mode, including the inner-outer diameter ratio in the ring illumination mode, the bi-peak spacing in the dipole illumination mode, or the four-quadrant energy balance in the quadrupole illumination mode.

[0014] The uniformity index is the ratio of the difference between the maximum and minimum illuminance to the average illuminance.

[0015] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0016] It also includes a light homogenization module and a mask surface monitoring module;

[0017] The beam homogenization module includes a first integrating rod, an adjustable gap assembly, and a second integrating rod arranged sequentially along the optical path. By adjusting the physical spacing of the adjustable gap assembly, the effective optical length and optical field coupling characteristics are changed, thereby homogenizing and shaping the beam.

[0018] The mask surface monitoring module samples the light beam through a beam splitter and guides the beam to a photodetector array located on the conjugate surface of the mask surface. It then acquires a two-dimensional light field uniformity distribution image of the exposure surface and calculates the uniformity index from each frame of the image to form a uniformity feature time series.

[0019] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0020] The uniform light module also includes a rotating mechanism and a microelectromechanical drive structure. The first integrating bar is mounted on the rotating mechanism to adjust the rotation angle around the optical axis, and the second integrating bar is connected to the microelectromechanical drive structure to adjust the cross-sectional size.

[0021] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0022] The zoom module is used to generate various off-axis lighting modes, including conventional lighting, ring lighting, dipole lighting, or quadrupole lighting.

[0023] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0024] According to the target illumination mode, a first control command is sent to the zoom module, and the zoom module is corrected based on the deviation between the actual pupil feature value collected by the pupil monitoring module and the target pupil feature value, until the deviation converges to within the first threshold.

[0025] After locking the optical parameters of the zoom module, a second control command is sent to the uniformity module. The uniformity index collected by the mask surface monitoring module optimizes the optical parameters of the uniformity module until the uniformity index reaches a second threshold.

[0026] Based on the effect of adjusting the optical parameters of the uniform light module on the total luminous flux, an adjustment command is simultaneously sent to the light source module to adjust the luminous intensity.

[0027] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0028] The decoupling controller is also used to construct a coupling matrix that characterizes the coupling relationship between the pupil eigenvalues ​​and the uniformity index;

[0029] Each element of the coupling matrix represents the transfer coefficient of the pupil eigenvalue change to the uniformity index;

[0030] The decoupling controller updates the coupling matrix based on real-time data from the pupil feature time series and the uniformity feature time series.

[0031] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0032] The decoupling controller also calculates a decoupling index based on historical data of the pupil feature time series and the uniformity feature time series. The decoupling index is used to characterize the degree of influence of pupil changes on uniformity. When the decoupling index exceeds a threshold, a system maintenance prompt is triggered.

[0033] As a preferred embodiment of the non-imaging lithography illumination system for an i-line lithography machine according to the present invention, wherein:

[0034] The method for calculating the decoupling degree index by the decoupling controller is as follows:

[0035] Select the pupil feature time series and the uniformity feature time series within a preset historical time period, and perform multi-scale wavelet decomposition on both to obtain their respective wavelet coefficients in different frequency bands;

[0036] Calculate the cross-correlation coefficients of wavelet coefficients in each frequency band to form a cross-correlation coefficient sequence;

[0037] The decoupling index is obtained by weighting the cross-correlation coefficient sequence, where the weight of the high-frequency band is lower than that of the low-frequency band.

[0038] The beneficial effects of this invention are:

[0039] This application uses a decoupling controller to perform empirical mode decomposition on the pupil feature time series and uniformity feature time series to obtain intrinsic mode function components at different time scales, identify mode pairs with matching center frequencies, and calculate the instantaneous phase difference time series through Hilbert transform. When the instantaneous phase difference is stable, it is determined that uniformity degradation is dominated by pupil drift; when the instantaneous phase difference is unstable, it is determined that it is dominated by the performance drift of the uniformity module. This achieves online quantification of coupling relationship and solves the problem of ambiguity and inability to identify the root cause of illumination faults online.

[0040] This application, through the analysis of instantaneous phase difference, determines that only the zoom module correction circuit is activated when the pupil drifts, and only the uniform light module correction circuit is activated when the uniform light module performance deteriorates. This selective activation strategy, based on root cause diagnosis, breaks through the mutual interference mode of the two circuits in serial correction, enabling the system to quickly converge to the rated operating point, thereby improving correction efficiency and the dynamic stability of the lighting system.

[0041] This application uses intrinsic mode function components at different scales obtained by empirical mode decomposition to evaluate the coupling state of high-frequency fluctuations and low-frequency drift, enabling the system to respond promptly in the early stages of drift occurrence, suppressing uniform fluctuations within the rated fluctuation range, and avoiding degradation caused by drift accumulation. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0043] Figure 1 This invention provides a schematic diagram of the overall structure and workflow of a non-imaging lithography illumination system for an i-line lithography machine.

[0044] Figure 2 This is a flowchart of the core algorithm of the decoupling controller for the non-imaging lithography illumination system of an i-line lithography machine according to the present invention;

[0045] Figure 3 This is a flowchart illustrating the real-time correction decision and selective activation process of a non-imaging lithography illumination system for an i-line lithography machine according to the present invention.

[0046] Figure 4 This is a flowchart illustrating the construction, updating, and maintenance of the coupling matrix of a non-imaging lithography illumination system for an i-line lithography machine according to the present invention. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0049] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0050] Example 1

[0051] like Figure 1 As shown, a non-imaging lithography illumination system for an i-line lithography machine includes:

[0052] The light source module uses an LED light source to provide the exposure beam in the i-line exposure band;

[0053] In a specific implementation, the light source module includes at least one LED chip and its packaging structure. The light source module can be integrated, for example, by arranging multiple high-power LED chips into an array and using a microlens array or light bar to perform preliminary light homogenization and focusing, forming an outgoing beam with a specific divergence angle and spot size, so as to efficiently couple into the subsequent zoom module and light homogenization module.

[0054] The zoom module changes the illumination coherence factor by adjusting the spacing of the internal lens group, thereby generating a preset off-axis illumination pupil distribution;

[0055] The zoom module is used to generate various off-axis lighting modes, including conventional lighting, ring lighting, dipole lighting, or quadrupole lighting.

[0056] In a specific embodiment, a preferred example of a zoom module may include at least two sets of lens groups that can move relative to each other along the optical axis, the lens groups being composed of one or more lenses.

[0057] By changing the spacing between the lens groups, the convergence or divergence angle of the light beam after passing through the zoom module can be adjusted, thereby changing the energy distribution pattern of the illumination beam on the pupil surface.

[0058] The illumination coherence factor is used to characterize the angular spectrum distribution characteristics of the illumination beam. The illumination coherence factor is the ratio of the numerical aperture of the illumination system to the numerical aperture of the projection lens. The illumination coherence factor can be continuously adjusted by changing the lens group spacing. When the lens group spacing increases the beam divergence angle, the illumination coherence factor increases, forming a full pupil distribution that is close to that of conventional illumination. When the lens group spacing increases the beam convergence angle, the illumination coherence factor decreases, forming a distribution that is close to that of small pupil.

[0059] Furthermore, the zoom module can generate a variety of preset off-axis illumination pupil distributions. The off-axis illumination is an illumination beam that illuminates the mask at an inclined angle, so that the zeroth order diffracted light and the ±1st order diffracted light can enter the projection lens simultaneously, thereby improving the imaging resolution and depth of focus.

[0060] The off-axis lighting modes include various off-axis lighting modes such as conventional lighting, ring lighting, dipole lighting, or quadrupole lighting.

[0061] To achieve the switching between the different illumination modes, specifically, the zoom module adjusts the lens group spacing to change the beam divergence angle, so that the beam is distributed at a specified angle and incident on the subsequent homogenizing module and pupil shaping element. The pupil shaping element can be a diffractive optical element or a specific prism group, used to redistribute the beam energy into the desired annular, dipole, or quadrupole shape.

[0062] The zoom module is electrically connected to the decoupling controller. The decoupling controller calculates the target pupil characteristic values ​​that the zoom module needs to achieve based on the preset target illumination mode, such as the inner-outer diameter ratio of ring illumination, the double-peak spacing of dipole illumination, or the four-quadrant energy balance of quadrupole illumination. The decoupling controller sends a first control command to the drive mechanism of the zoom module to drive the lens group to move to the target position, thereby generating the corresponding off-axis illumination pupil distribution.

[0063] The pupil monitoring module acquires two-dimensional energy distribution images of the illumination pupil and extracts pupil feature values ​​that characterize the pupil morphology from each frame image to form a pupil feature time series.

[0064] A preferred method for acquiring two-dimensional energy distribution images includes:

[0065] The pupil monitoring module acquires the image of the illumination pupil through optical sampling and sets a beam splitter along the illumination optical path. The beam splitter is located at the position where the light-emitting side of the zoom module is optically conjugate with the pupil surface.

[0066] The pupil conjugate surface is a plane that is optically conjugate with the real pupil surface of the illumination system after imaging by the optical system. By placing a photodetector array on the conjugate plane, a clear image of the illumination pupil can be obtained.

[0067] A relay optical system consisting of a set of lenses is used to accurately image the beam at the beam splitter onto the detector target surface and match the detector size with the magnification of the pupil image.

[0068] The photodetector array is preferably a two-dimensional array detector, such as a charge-coupled device image sensor or a complementary metal-oxide-semiconductor image sensor. The photodetector array distinguishes the energy differences in different regions on the pupil surface. The exposure time of the detector array is synchronized with the exposure cycle of the lithography machine, for example, by continuously acquiring data from 1 to 10 frames per second to obtain a sequence of two-dimensional energy distribution images of the illumination pupil that change over time.

[0069] The pupil feature value is a quantitative index of the pupil shape selected according to the current illumination mode, including the inner-outer diameter ratio in the ring illumination mode, the bi-peak spacing in the dipole illumination mode, or the four-quadrant energy balance in the quadrupole illumination mode.

[0070] Pupil feature values ​​are indicators extracted from two-dimensional energy distribution images and used to quantify the pupil morphology. Different off-axis illumination modes correspond to different pupil morphologies, so different feature values ​​need to be selected for quantification. This application adaptively selects the corresponding pupil feature values ​​according to the current illumination mode.

[0071] Specifically, in the ring illumination mode, the energy distribution on the pupil surface is in the shape of a ring band. In the two-dimensional energy distribution image, the energy in the central region is lower, the energy in the ring region is higher, and the energy in the outer region is lower.

[0072] It should be noted that in the ring illumination mode, the inner diameter refers to the distance from the inner boundary of the ring to the center of the pupil, and the outer diameter refers to the distance from the outer boundary of the ring to the center of the pupil. The ratio of the inner diameter to the outer diameter is used to reflect the width and position of the ring.

[0073] Furthermore, on the two-dimensional energy distribution image, the pupil center is first determined, which is the geometric center of the image. Then, energy sampling is performed from the center outward to obtain the radial energy distribution curve. By using a preset energy threshold, such as 50% or 80% of the peak energy, the inner diameter position corresponding to the energy rising to the threshold and the outer diameter position corresponding to the energy falling to the threshold on the radial curve are determined, and then the inner-outer diameter ratio is calculated.

[0074] In dipole illumination mode, the energy on the pupil surface is concentrated in two symmetrical regions, forming two separate energy peaks. For example, the two peaks of the dipole in the X direction are located on the left and right sides respectively. The distance between the two peaks is a parameter used to describe the dipole morphology.

[0075] The bi-peak spacing refers to the distance between the centers of the two energy peaks. This distance reflects the tilt angle of off-axis illumination and directly affects imaging resolution and depth of focus.

[0076] On a two-dimensional energy distribution image, the pupil center is first determined, and then the image is projected and integrated along the dipole direction, such as the X or Y direction, to obtain a one-dimensional energy distribution curve. Local maxima are found through peak detection, the pixel coordinates of the two peaks are determined, the pixel distance between the two peak positions is calculated, and combined with the pixel size and imaging magnification, it is converted into the actual distance on the pupil surface, which is the double-peak spacing.

[0077] In the four-electrode illumination mode, the energy on the pupil surface is concentrated in four symmetrical regions, distributed in the upper left, upper right, lower left, and lower right quadrants. The energy balance in the four quadrants is a parameter describing the four-electrode morphology.

[0078] The four-quadrant energy uniformity refers to the uniformity of accumulated energy within the four quadrants, characterized by the ratio of the maximum to minimum energy values ​​in the four quadrants. The four-quadrant energy uniformity is used to reflect whether the illumination intensity of the four quadrants is consistent, affecting the symmetry of the exposure of two-dimensional graphics.

[0079] On the two-dimensional energy distribution image, the center of the pupil is first determined, and a cross coordinate system is established to divide the pupil into four quadrants. In each quadrant, the gray values ​​of the detector pixels are summed to obtain the total energy of the four quadrants Q1, Q2, Q3, and Q4. Then, the uniformity index of these four values ​​is calculated, for example, (Qmax-Qmin) / (Qmax+Qmin) as the quantization value of the energy balance of the four quadrants.

[0080] In this application, a preferred method for extracting pupil feature values ​​specifically includes:

[0081] The process of extracting pupil feature values ​​from each frame of a two-dimensional energy distribution image includes:

[0082] First, due to factors such as detector noise and ambient light interference, the original image may contain noise. Preprocessing includes removing background noise when there is no light, correcting inconsistencies in detector pixel response, and image filtering, such as median filtering or Gaussian filtering, to obtain image data with high signal-to-noise ratio and good quality.

[0083] Secondly, based on the current lighting mode set by the system, the corresponding feature extraction algorithm is invoked. The decoupling controller stores multiple feature extraction algorithms and automatically selects one based on the target lighting mode.

[0084] Then, the feature extraction algorithm is executed:

[0085] For ring lighting, perform center positioning, radial energy integration, threshold segmentation, boundary detection, and calculate the inner-outer diameter ratio.

[0086] For dipole lighting, perform center positioning, directional projection, peak detection, and calculate the distance between the two peaks.

[0087] For four-pole lighting, the process involves center positioning, quadrant division, energy integration, and statistical calculation to obtain the energy balance of the four quadrants.

[0088] Finally, multiple values ​​are output as pupil feature values ​​for the current frame. These pupil feature values ​​are single-precision or double-precision floating-point numbers used to represent the morphological characteristics of the illumination pupil at the current moment.

[0089] The uniformity index is the ratio of the difference between the maximum and minimum illuminance to the average illuminance.

[0090] The pupil monitoring module continuously acquires two-dimensional energy distribution images of the illumination pupil at a fixed sampling frequency. For each frame of the acquired image, the corresponding pupil feature values ​​are extracted in real time to obtain a scalar of the inner-outer diameter ratio or a vector containing multiple parameters such as the inner-outer diameter ratio and the average radius.

[0091] The pupil feature values ​​are stored in chronological order to form a pupil feature time series. Specifically, each frame of the image corresponds to a timestamp ti and a set of feature values ​​P(ti). The data of all frames are organized in chronological order to obtain the sequence {P(t1),P(t2),P(t3),...,P(tn)}.

[0092] The pupil feature time series is sent to the decoupling controller in real time as input data for empirical mode decomposition, frequency domain analysis, and phase difference calculation. By analyzing the correlation between this series and the uniformity feature time series, the system can accurately determine the causal relationship between pupil drift and uniformity degradation.

[0093] After the lithography illumination system is started, the illumination mode is switched, or it has been running for a long time, an initial calibration is required to enable the system to quickly enter a stable working state.

[0094] The zoom module is sent a first control command according to the target illumination mode, and the zoom module is fed back to correct the deviation between the actual pupil feature value and the target pupil feature value collected by the pupil monitoring module until the deviation converges to within the first threshold.

[0095] When the system receives a new target lighting mode instruction, such as switching from conventional lighting to ring lighting, or loading a preset process recipe when the system starts, the decoupling controller first executes the feedback correction process of the zoom module.

[0096] Specifically, the decoupling controller retrieves or calculates the target pupil feature value corresponding to the current illumination mode from its internal memory, based on the target illumination mode. For ring illumination mode, the target pupil feature value can be a preset inner-outer diameter ratio; for dipole illumination mode, the target feature value is a preset bi-peak spacing; and for quadrupole illumination mode, the target feature value is a preset four-quadrant energy equalization. These target values ​​are typically predetermined and stored in the system by the lithography process engineer based on the requirements of the specific exposure pattern.

[0097] The decoupling controller sends a first control command to the drive mechanism of the zoom module. The first control command contains the initial target position information of the lens group inside the zoom module, drives the lens group to move to the preset initial position, and generates a preliminary off-axis illumination pupil distribution.

[0098] During and after the zoom module's operation, the pupil monitoring module continuously acquires two-dimensional energy distribution images of the illumination pupil at a fixed sampling frequency and extracts the actual pupil feature values ​​in real time. The decoupling controller receives the actual pupil feature values ​​and compares them with the target pupil feature values ​​to calculate the deviation between the two.

[0099] The deviation is an absolute deviation, i.e., the actual value minus the target value. The decoupling controller calculates the correction amount using a PID control algorithm based on the magnitude and direction of the deviation, generates an updated first control command, and sends it again to the drive mechanism of the zoom module to fine-tune the spacing of the lens group. The PID control algorithm can be conventionally set by those skilled in the art in conjunction with the content disclosed in this application.

[0100] A feedback control loop is formed by collecting and calculating deviations and sending correction commands until the deviation between the actual pupil feature value and the target pupil feature value converges within a first threshold. The first threshold is a preset allowable error range, such as a deviation of less than 0.01 in the inner-outer diameter ratio or a deviation of less than 0.5 mm in the distance between the two peaks. When the deviation remains stable within this threshold range, the decoupling controller determines that the zoom module has completed the correction and the pupil distribution has reached the target state.

[0101] After locking the optical parameters of the zoom module, a second control command is sent to the uniformity module. The uniformity index collected by the mask surface monitoring module optimizes the optical parameters of the uniformity module until the uniformity index reaches a second threshold.

[0102] After the zoom module has completed calibration and the pupil distribution has been locked, the decoupling controller locks the optical parameters of the zoom module, that is, it stops sending further adjustment commands to the zoom module, so that it keeps the current lens group spacing unchanged.

[0103] Furthermore, the decoupling controller initiates the optimization process of the light homogenizing module and sends a second control command to the light homogenizing module. The light homogenizing module includes a first integrating rod, an adjustable gap component, and a second integrating rod arranged sequentially along the optical path. The second control command is used to adjust the physical spacing of the adjustable gap component, change the effective optical length and light field coupling characteristics of the light homogenizing module, and realize the adjustment of the uniformity of the exposure surface.

[0104] During the adjustment of the uniform light module, the mask surface monitoring module acquires a two-dimensional light field uniformity distribution image of the exposure surface in real time, and calculates the current uniformity index from each frame of the image. The uniformity index is defined as the ratio of the difference between the maximum and minimum illuminance on the exposure surface to the average illuminance. The smaller the value of the ratio, the better the uniformity.

[0105] The decoupling controller receives real-time uniformity indicators from the mask surface monitoring module and uses these indicators as optimization targets to guide the parameter adjustment of the homogenizing module. Since the relationship between the homogenizing module's adjustment and the uniformity indicator is non-linear, the decoupling controller can employ various optimization strategies. For example, a step search approach can be used, gradually changing the adjustable gap spacing in small steps, observing the trend of the uniformity indicator's changes, and finding the optimal spacing value that optimizes the uniformity indicator.

[0106] The optimization process continues until the uniformity index reaches or exceeds a preset second threshold. The second threshold is set according to the requirements of the photolithography process for exposure uniformity at the factory or in production. For example, the uniformity index is required to be better than ±1% or better than ±0.5%. When the real-time uniformity index fed back by the mask surface monitoring module is consistently and stably better than this threshold, the decoupling controller determines that the uniformity module has completed optimization and the uniformity of the exposure surface has met the process requirements.

[0107] Based on the effect of adjusting the optical parameters of the uniform light module on the total luminous flux, an adjustment command is simultaneously sent to the light source module to adjust the luminous intensity.

[0108] In the process of optimizing the uniformity of the light homogenizing module, adjusting the physical spacing of the adjustable gap components may cause changes in the total luminous flux of the system.

[0109] Specifically, changing the gap between the first and second integrating bars will affect the coupling efficiency of the beam between the two integrating bars, resulting in a change in the total light energy after passing through the homogenizing module. If no compensation is made at this time, even if the uniformity meets the requirements, the exposure dose reaching the mask surface will deviate from the preset value, affecting the stability of the photolithography process.

[0110] While sending the second control command to the light homogenizing module, the decoupling controller calculates the impact on the total luminous flux based on the adjustment amount of the optical parameters of the light homogenizing module.

[0111] Specifically, the decoupling controller stores a pre-calibrated luminous flux gap relationship lookup table, which describes the relative rate of change of the total luminous flux of the system under different adjustable gap spacings. When the decoupling controller determines the target gap value, that is, the gap value at which the uniformity reaches the second threshold, it predicts the change in the total luminous flux by querying the luminous flux gap relationship lookup table.

[0112] A preferred lookup table for luminous flux gap relationships is shown below:

[0113] ;

[0114] Based on the predicted changes in luminous flux, the decoupling controller calculates the amount of luminous intensity adjustment that needs to be compensated. If the adjustment of the uniform light module causes a decrease in luminous flux, the luminous intensity of the light source module needs to be increased; if it causes an increase in luminous flux, the luminous intensity needs to be reduced.

[0115] Furthermore, the decoupling controller synchronously sends adjustment commands to the light source module. These adjustment commands change the driving current of the LED driving circuit to adjust the luminous intensity of the LED chip, thereby ensuring that the final exposure dose after passing through the homogenizing module is consistent with the target dose set in the process formula.

[0116] This application achieves the optimization of exposure surface uniformity while maintaining a constant exposure dose. The light homogenization module is used to improve the energy distribution pattern of the light spot, making the energy distribution pattern more uniform. The light source module is used to compensate for the energy loss or gain caused by light homogenization adjustment, ensuring that the total energy remains unchanged. Through a step-by-step serial and synchronous linkage control strategy, the comprehensive optimization of pupil distribution, illumination uniformity and exposure dose is achieved.

[0117] A non-imaging lithography illumination system for an i-line lithography machine also includes a light homogenizing module and a mask surface monitoring module;

[0118] The beam homogenization module includes a first integrating rod, an adjustable gap assembly, and a second integrating rod arranged sequentially along the optical path. By adjusting the physical spacing of the adjustable gap assembly, the effective optical length and optical field coupling characteristics are changed, thereby homogenizing and shaping the beam.

[0119] In a specific implementation, the light homogenizing module includes a first integrating rod, an adjustable gap assembly, and a second integrating rod arranged sequentially along the optical path.

[0120] It should be noted that the integrating rod is an optical element that uses the principle of total internal reflection to achieve beam homogenization. When the beam enters the integrating rod, the light undergoes multiple total internal reflections inside the rod, forming a uniform energy distribution on the exit end face.

[0121] The first and second integrating rods are solid glass rods with rectangular or polygonal cross-sections. For the i-band, the solid integrating rod is preferably made of fused silica, which utilizes total internal reflection to conduct light. The cross-sectional shape of the integrating rod can be rectangular.

[0122] An adjustable gap assembly is positioned between the first and second integrating bars to connect the two bars and allow for changes in the physical distance between them. The adjustable gap assembly includes a linear guide and a drive mechanism, such as a piezoelectric ceramic driver, a voice coil motor, or a stepper motor with a ball screw. The first integrating bar is fixedly mounted, while the second integrating bar is mounted on a movable platform. The drive mechanism moves the second integrating bar relative to the first integrating bar along the optical axis, thus changing the air gap between the two integrating bars.

[0123] Adjusting the physical spacing of the adjustable gap components can change the effective optical length and light field coupling characteristics of the homogenizing module, thereby adjusting the uniformity of the exposure surface. Specifically, this includes:

[0124] The first integrating rod performs preliminary homogenization of the incident beam, forming a relatively uniform light spot at the exit end. The light spot enters the second integrating rod after passing through the air gap. When the gap distance is small, the light spot emitted from the first integrating rod is almost directly coupled into the second integrating rod. The second integrating rod mainly plays the role of supplementing homogenization and transmission. When the gap distance increases, the beam will undergo a certain degree of free propagation in the air, the light spot size will diverge slightly, and the incident angle distribution when entering the second integrating rod will also change.

[0125] By adjusting the gap distance, the uniformity distribution of the final emitted light spot can be fine-tuned.

[0126] Furthermore, the homogenizing module may also include a rotating mechanism and a microelectromechanical (MEMS) drive structure to achieve more dimensional adjustments. A first integrating rod is mounted on the rotating mechanism, which drives the first integrating rod to rotate around the optical axis to adjust the direction of the emitted light spot or compensate for energy distribution asymmetry caused by assembly errors of optical components. A second integrating rod is connected to the MEMS drive structure, which can finely adjust the cross-sectional position of the second integrating rod along a direction perpendicular to the optical axis, thereby optimizing the optical field coupling efficiency and uniformity.

[0127] The uniform light module is electrically connected to the decoupling controller. The decoupling controller sends a second control command to the uniform light module according to the initialization correction process or real-time correction requirements. The second control command includes the target gap distance, target rotation angle or target cross-sectional position. The drive mechanism of the uniform light module performs corresponding actions according to the command and adjusts the optical parameters until the uniformity index fed back by the mask surface monitoring module reaches the preset threshold.

[0128] The mask surface monitoring module samples the light beam through a beam splitter and guides the beam to a photodetector array located on the conjugate surface of the mask surface. It then acquires a two-dimensional light field uniformity distribution image of the exposure surface and calculates the uniformity index from each frame of the image to form a uniformity feature time series.

[0129] The mask surface monitoring module acquires the image of the mask surface through optical sampling. In a specific embodiment, a beam splitter is set along the illumination optical path. The beam splitter is located between the light-emitting side of the light-uniforming module and the mask surface. The beam splitter adopts partial reflection and partial transmission. Without affecting the exposure energy of the main optical path, a small portion of the beam is branched out for monitoring the beam.

[0130] The sampled beam reflected by the beam splitter is guided by a relay optical system to a photodetector array located on the conjugate surface of the mask. The conjugate surface of the mask is the plane that is optically conjugate to the actual mask after imaging by the optical system. By placing the photodetector array on the optically conjugate plane, a clear image of the exposure light field of the mask can be obtained.

[0131] The uniformity index used in this application is defined as the ratio of the difference between the maximum and minimum illuminance to the average illuminance. The specific calculation method is as follows:

[0132] Count the grayscale values ​​of all pixels within the effective exposure area, and find the maximum value Imax and the minimum value Imin.

[0133] Calculate the arithmetic mean Iavg of the grayscale values ​​of all pixels within the effective exposure area.

[0134] Calculate the maximum and minimum illuminance difference Imax-Imin.

[0135] Comparing the above difference with the average illuminance, we obtain the uniformity index U=(Imax-Imin) / Iavg. The smaller the value, the better the uniformity.

[0136] Output a floating-point number as the uniformity index for the current frame. This value represents the illumination uniformity level of the exposed surface at the current moment.

[0137] The mask surface monitoring module continuously acquires images of the exposure surface at a fixed sampling frequency. For each frame of the acquired image, a uniformity index is calculated in real time to obtain a scalar value. The uniformity indexes, arranged in chronological order, are stored to form a uniformity feature time series. Specifically, each frame of the image corresponds to a timestamp and a uniformity index value U(ti).

[0138] The data from all frames are organized in chronological order to obtain the sequence {U(t1),U(t2),U(t3),...,U(tn)}.

[0139] The uniformity feature time series is sent to the decoupled controller in real time as the basic input data for subsequent empirical mode decomposition, frequency domain analysis and phase difference calculation.

[0140] The uniform light module also includes a rotating mechanism and a microelectromechanical drive structure. The first integrating bar is mounted on the rotating mechanism to adjust the rotation angle around the optical axis, and the second integrating bar is connected to the microelectromechanical drive structure to adjust the cross-sectional size.

[0141] In this application, a preferred implementation method of the rotating mechanism includes:

[0142] The rotating mechanism is installed around the first integrating bar to support it and drive it to rotate around the optical axis. The rotating mechanism includes a rotating platform, a bearing system, and a drive unit. The rotating platform has a hollow structure, and the first integrating bar is fixedly installed in its hollow portion, ensuring that the optical axis of the integrating bar coincides with the rotation axis of the rotating platform. The bearing system uses crossed roller bearings to ensure smooth rotation and repeatability. The drive unit can use a direct-drive torque motor or a stepper motor in conjunction with a worm gear reducer to achieve high torque and low speed angle control.

[0143] By rotating the first integrating bar, the reflection path and reflection frequency distribution of light within the integrating bar can be altered, thereby compensating for and optimizing the angular energy distribution of the emitted light spot. For example, when the exposure surface uniformity is detected to be darker in a specific direction, rotating the first integrating bar can adjust the edge of the integrating bar corresponding to the current direction to a more favorable position, allowing more light to couple into the current direction and improving angular uniformity. The adjustment range of the rotating mechanism is from 0° to 360°, achieving uniformity compensation.

[0144] The rotating mechanism is electrically connected to the decoupling controller. Based on the uniformity index fed back by the mask surface monitoring module, the decoupling controller sends a rotation angle command to the rotating mechanism. The rotating mechanism drives the first integrating bar to rotate to the target angle, so that the uniformity of the exposure surface reaches the optimal state.

[0145] In this application, a preferred embodiment of a microelectromechanical drive structure includes:

[0146] The microelectromechanical drive structure is connected to the second integrator and is used to adjust the cross-sectional size of the second integrator. The microelectromechanical drive structure uses miniaturized drivers and transmission mechanisms to achieve fine-tuning of the second integrator.

[0147] In a specific embodiment, the microelectromechanical drive structure includes multiple micro piezoelectric actuators distributed along the axial direction of the second integrating rod. When a control voltage is applied, the actuators generate minute displacements or deformations, which are then transmitted to the target part of the second integrating rod through a lever amplification mechanism, thereby changing the cross-sectional geometric parameters of the integrating rod.

[0148] Adjusting the cross-sectional dimensions adjusts the uniform light characteristics of the uniform light module to adapt to different lighting conditions. The cross-sectional shape and size of the integrating rod directly affect the reflection angle and pattern distribution of light on the inner wall. By fine-tuning the cross-sectional dimensions, such as by slightly stretching or compressing the rectangular cross-section in the width direction, the aspect ratio and far-field energy distribution of the emitted light spot can be changed, thereby achieving fine-tuning of the uniformity of the exposure surface.

[0149] Adjusting the beam divergence angle distribution compensates for the impact of pupil changes caused by zoom module adjustment on the homogenization effect; fine-tuning the edge sharpness of the light spot improves the illumination uniformity of the mask surface edge area; compensating for thermal expansion or refractive index changes in the integrating rod material caused by temperature changes, maintaining the stability of homogenization performance.

[0150] For example, during the system initialization and calibration phase, the uniformity is first optimized to near the second threshold using the adjustable gap component. Then, based on the angular uniformity information fed back by the mask surface monitoring module, the angle of the first integrating bar is finely adjusted via the rotation mechanism to further improve the uniformity. Finally, the cross-sectional dimensions of the second integrating bar are finely adjusted via the microelectromechanical drive structure to optimize the uniformity to the optimal state. During the real-time operation phase of the system, when a small fluctuation in uniformity is detected, the microelectromechanical drive structure is used first for rapid response compensation. Only when the compensation range is insufficient is the adjustable gap component activated for a larger range of adjustment.

[0151] The hierarchical and multi-dimensional adjustment not only ensures high-precision control of uniformity, but also improves the system's response speed and stability.

[0152] The decoupling controller receives the pupil feature time series and the uniformity feature time series, and performs empirical mode decomposition to obtain intrinsic mode function components at different time scales. From the intrinsic mode function components of the pupil feature time series and the intrinsic mode function components of the uniformity feature time series, it identifies the intrinsic mode function components with matching center frequencies, performs Hilbert transform on the intrinsic mode function components with matching center frequencies, calculates the instantaneous phase difference time series, and activates the correction loop for the zoom module and the correction loop for the uniformity module.

[0153] The decoupling controller is also used to construct a coupling matrix that characterizes the coupling relationship between the pupil eigenvalues ​​and the uniformity index;

[0154] Each element of the coupling matrix represents the transfer coefficient of the pupil eigenvalue change to the uniformity index;

[0155] The decoupling controller updates the coupling matrix based on real-time data from the pupil feature time series and the uniformity feature time series.

[0156] The decoupling controller receives in real time the pupil feature time series from the pupil monitoring module and the uniformity feature time series from the mask surface monitoring module. The pupil feature time series is denoted as P(t), representing the change of the pupil feature value over time; the uniformity feature time series is denoted as U(t), representing the change of the uniformity index over time.

[0157] The decoupled controller performs data cleaning and preprocessing on the two time series. The preprocessing steps include: removing outliers caused by transient interference from the sensors, such as using median filtering to remove outliers; interpolating to complete the data at times with missing data; and normalizing the series to eliminate the impact of differences in the dimensions of different feature values ​​on subsequent analysis.

[0158] The decoupling controller is also used to construct and update a coupling matrix that characterizes the coupling relationship between pupil eigenvalues ​​and uniformity indices. This coupling matrix can be used for system state monitoring, fault diagnosis, and control parameter optimization.

[0159] like Figure 4 As shown, the coupling matrix C is an m×n matrix, where m is the number of pupil eigenvalues, such as the inner-outer diameter ratio, bimodal spacing, and four-quadrant energy uniformity, and n is the number of uniformity indices. The number of uniformity indices can be set to 1 (i.e., a single uniformity index), but can also be extended to uniformity indices in multiple regions or multiple dimensions. Each element of the matrix... This represents the transfer coefficient of the change in the i-th pupil feature value to the j-th uniformity index, i.e., sensitivity.

[0160] In a specific implementation, the initial value of the coupling matrix can be obtained through system calibration. While the system is offline, each pupil feature value is changed sequentially, the change in uniformity index is recorded, the rate of change is calculated as the transfer coefficient, and then filled into the coupling matrix.

[0161] During system online operation, the decoupling controller updates the coupling matrix online based on the real-time acquired pupil feature time series and uniformity feature time series. For example, a sliding window regression method is used: selecting a recent time window, such as the pupil feature value data ΔP and uniformity index data ΔU within the past 100 sampling points, to establish a multiple linear regression model ΔU=C. ΔP+ The updated coupling matrix C is obtained by solving the least squares method. By monitoring the changing trends of the elements in the coupling matrix, it is possible to determine whether an anomaly has occurred in the system. For example, if a certain transfer coefficient suddenly increases, it may indicate an enhanced coupling relationship between the corresponding pupil feature and uniformity, where ΔU is the data vector of changes in the uniformity index within the sliding window, and ΔP is the data vector of changes in the pupil feature value within the sliding window. This represents the error term in the multiple linear regression model.

[0162] When uniformity deteriorates, the contribution of pupil drift to uniformity deterioration can be estimated by combining the coupling matrix and pupil change, thus assisting in fault location.

[0163] The decoupling controller also calculates a decoupling index based on historical data of the pupil feature time series and the uniformity feature time series. The decoupling index is used to characterize the degree of influence of pupil changes on uniformity. When the decoupling index exceeds a threshold, a system maintenance prompt is triggered.

[0164] like Figure 2 As shown, the decoupling controller performs empirical mode decomposition on the preprocessed pupil feature time series P(t) and uniformity feature time series U(t), respectively.

[0165] Empirical mode decomposition (EMD) decomposes complex nonlinear and nonstationary signals into several intrinsic mode function components and residual terms, as described in specific implementations.

[0166] For a given time series X(t), specific implementation methods for obtaining intrinsic mode function components through empirical mode decomposition include:

[0167] First, identify all local maxima and local minima of the sequence X(t). Then, use cubic spline interpolation to connect all local maxima to form the upper envelope. Connect all local minima to form the lower envelope. Calculate the mean of the upper and lower envelopes. Subtracting the mean from the original sequence yields the detail component h(t) = X(t) - Used to determine whether the intrinsic modulus function condition is met.

[0168] To determine whether h(t) satisfies the two conditions for an eigenfunction: the number of extreme points is equal to or differs by at most one from the number of zero-crossing points throughout the entire data sequence; and at any given time, the mean of the upper envelope formed by local maxima and the lower envelope formed by local minima is zero. If h(t) satisfies these two conditions, it is considered the first eigenfunction component. If the conditions are not met, then h(t) is used as a new sequence, and the above screening process is repeated until the intrinsic modulus function components that meet the conditions are obtained.

[0169] The first intrinsic modulus component is obtained. Then, calculate the residual components. ,Will As a new sequence, the above decomposition process is repeated to obtain the second intrinsic modulus function component. The third until the residual component It becomes a monotonic function or a constant, until it can no longer be decomposed into eigenmodular components.

[0170] It should be noted that, The k-th eigenmode function component represents the oscillation mode of the original signal at a specific time scale. The frequency is highest at k, and decreases as k increases.

[0171] Through empirical mode decomposition, the pupil feature time series P(t) is decomposed into several intrinsic mode function components { } and a residual term Similarly, the uniformity characteristic time series U(t) is decomposed into { }and These intrinsic mode function components represent the oscillation modes of the original sequence at different time scales, where... The highest frequency oscillations correspond to rapid fluctuations caused by mechanical vibrations. The larger the IMF number, the lower the corresponding frequency, such as medium-speed changes caused by temperature drift and long-term drift caused by component aging. The residual term r(t) represents the overall trend of the sequence.

[0172] It should be noted that, The center frequency of the nth intrinsic mode function component in the pupil feature time series;

[0173] The center frequency of the nth intrinsic modulus function component of the uniform characteristic time series;

[0174] After obtaining two sets of intrinsic mode function components, the decoupling controller needs to identify mode pairs with matching center frequencies from the components of P(t) and U(t), that is, those components that oscillate in the same frequency band.

[0175] In a specific implementation, the decoupling controller includes a spectrum analysis module. Spectrum analysis is performed on each intrinsic mode function component to extract its center frequency. The specific method is as follows:

[0176] For each intrinsic modulus function component imf(t), a Fast Fourier Transform is performed to obtain its spectral distribution. The frequency component with the highest energy, i.e., the main peak frequency, is identified in the spectrum and used as the center frequency of that component.

[0177] After spectral analysis, the set of center frequencies of each component of P(t) is obtained { , ,..., The set of center frequencies of each component of U(t) , ,..., }

[0178] Then, the frequency matching module executes the matching algorithm. For each component of P(t), it searches for the component in U(t) whose center frequency is closest to it. If the difference between the center frequencies of the two components is less than a preset frequency tolerance threshold, for example, the relative deviation of the two frequencies is less than 5%, or the absolute deviation is less than 0.01Hz, then the two components are determined to be a mode pair with matched center frequencies.

[0179] Through the above matching process, a series of matching mode pairs {( , ),( , ),...}, each pair represents the pupil variation and uniformity variation oscillating in the same frequency band.

[0180] For each pair of intrinsic mode function components with matched center frequencies, the decoupling controller performs a Hilbert transform on them to extract instantaneous phase information and calculate the instantaneous phase difference time series.

[0181] In a specific implementation, the decoupling controller includes a Hilbert transform module and a phase difference calculation module. For a real signal s(t), the Hilbert transform is defined as:

[0182]

[0183] The analytic signal z(t) = s(t) + j can be constructed using the Hilbert transform. =A(t) , where A(t) is the instantaneous amplitude, Φ(t) is the instantaneous phase, and t represents time.

[0184] It is important to note that Let be the Hilbert transform of the real signal s(t);

[0185] z(t) is an analytic signal;

[0186] The Hilbert transform module transforms each pair of matched mode pairs separately:

[0187] right Perform a Hilbert transform to obtain its instantaneous phase time series. That is, the instantaneous phase time sequence of the pupil feature matching component.

[0188] right Perform a Hilbert transform to obtain its instantaneous phase time series. That is, the instantaneous phase time series of the uniformity feature matching component.

[0189] The phase difference calculation module subtracts the instantaneous phases of the same mode pair to obtain the instantaneous phase difference time series:

[0190] ΔΦ(t)= -

[0191] The instantaneous phase difference ΔΦ(t) reflects the phase relationship between pupil change and uniformity change in the frequency band. If both change synchronously, i.e., the pupil change immediately causes a uniformity change, the instantaneous phase difference should remain relatively stable, fluctuating slightly around a constant. If the two change asynchronously, the instantaneous phase difference will fluctuate significantly over time.

[0192] Based on the analysis results of the instantaneous phase difference time series, the decoupling controller selectively activates the correction loop for the zoom module or the correction loop for the homogenizing module. The selective activation strategy is used to determine whether the root cause of the uniformity degradation is the secondary effect caused by pupil drift or the performance degradation of the homogenizing module itself.

[0193] If the fluctuation range of the instantaneous phase difference time series is less than the preset phase threshold, it is determined that the uniformity degradation is dominated by pupil drift, and the correction loop of the zoom module is activated.

[0194] If the fluctuation range of the instantaneous phase difference time series is greater than or equal to the preset phase threshold, it is determined that the uniformity degradation is dominated by the performance drift of the uniform light module, and the correction loop for the uniform light module is activated.

[0195] The fluctuation range can be quantified using statistics such as the standard deviation of the instantaneous phase difference, the peak-to-peak value, or the variance within a sliding window. The preset phase threshold can be pre-calibrated based on the noise level and process requirements of the actual system, for example, set to ±10° or ±20°.

[0196] When the primary cause is determined to be pupil drift, the decoupling controller sends a correction command to the zoom module to correct the pupil shape by finely adjusting the lens group spacing, thereby eliminating the factors that cause uniformity degradation from the root. When the primary cause is determined to be light leveling module performance drift, the decoupling controller sends a correction command to the light leveling module to restore the uniformity of the exposure surface by adjusting the physical spacing of the adjustable gap components.

[0197] The method for calculating the decoupling degree index by the decoupling controller is as follows:

[0198] Select the pupil feature time series and the uniformity feature time series within a preset historical time period, and perform multi-scale wavelet decomposition on both to obtain their respective wavelet coefficients in different frequency bands;

[0199] It should be noted that wavelet coefficients are the coefficients obtained in different frequency bands after multi-scale wavelet decomposition of the historical time series.

[0200] The cross-correlation coefficient is a measure of the correlation between wavelet coefficients in each frequency band, reflecting the coupling strength between the pupil and uniformity in that frequency band.

[0201] The decoupling index is a comprehensive index obtained by weighted averaging of the cross-correlation coefficient series, used to characterize the degree of influence of pupil variation on uniformity.

[0202] Calculate the cross-correlation coefficients of wavelet coefficients in each frequency band to form a cross-correlation coefficient sequence;

[0203] The decoupling index is obtained by weighting the cross-correlation coefficient sequence, where the weight of the high-frequency band is lower than that of the low-frequency band.

[0204] If the fluctuation range of the instantaneous phase difference time series is less than the preset phase threshold, it is determined that the uniformity degradation is dominated by pupil drift, and the correction circuit of the zoom module is activated.

[0205] If the fluctuation range of the instantaneous phase difference time series is greater than or equal to the preset phase threshold, it is determined that the uniformity degradation is dominated by the performance drift of the uniform light module, and the correction loop for the uniform light module is activated.

[0206] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0207] It should be understood that numerous specific implementation decisions can be made during the development of any actual implementation method, and in any engineering or design project. Such development efforts may be complex and time-consuming, but for those of ordinary skill in the art who benefit from this disclosure, the development effort will be a routine task in design, manufacturing, and production without requiring extensive experimentation.

[0208] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A non-imaging lithography illumination system for an i-line lithography machine, characterized in that, include: The light source module uses an LED light source to provide the exposure beam in the i-line exposure band; The zoom module changes the illumination coherence factor by adjusting the spacing of the internal lens group, thereby generating a preset off-axis illumination pupil distribution; The pupil monitoring module acquires two-dimensional energy distribution images of the illumination pupil and extracts pupil feature values ​​that characterize the pupil morphology from each frame image to form a pupil feature time series. The pupil feature value is a quantitative index of the pupil shape selected according to the current illumination mode, including the inner-outer diameter ratio in the ring illumination mode, the bi-peak spacing in the dipole illumination mode, or the four-quadrant energy balance in the quadrupole illumination mode. The uniformity index is the ratio of the difference between the maximum and minimum illuminance to the average illuminance; It also includes a light homogenization module and a mask surface monitoring module; The beam homogenization module includes a first integrating rod, an adjustable gap assembly, and a second integrating rod arranged sequentially along the optical path. By adjusting the physical spacing of the adjustable gap assembly, the effective optical length and optical field coupling characteristics are changed, thereby homogenizing and shaping the beam. The mask surface monitoring module samples the light beam through a beam splitter and guides the light beam to a photodetector array located on the conjugate surface of the mask surface, acquires a two-dimensional light field uniformity distribution image of the exposure surface, and calculates the uniformity index from each frame of the image to form a uniformity feature time series. The decoupling controller receives the pupil feature time series and the uniformity feature time series, and performs empirical mode decomposition to obtain intrinsic mode function components at different time scales. From the intrinsic mode function components of the pupil feature time series and the intrinsic mode function components of the uniformity feature time series, it identifies the intrinsic mode function components with matching center frequencies, performs Hilbert transform on the intrinsic mode function components with matching center frequencies, calculates the instantaneous phase difference time series, and activates the correction loop for the zoom module and the correction loop for the uniformity module.

2. The non-imaging lithography illumination system for an i-line lithography machine according to claim 1, characterized in that: The zoom module is used to generate various off-axis lighting modes, including conventional lighting, ring lighting, dipole lighting, or quadrupole lighting. The pupil monitoring module samples the light beam through a beam splitter and guides the beam to a photodetector array located on the conjugate surface of the pupil.

3. The non-imaging lithography illumination system for an i-line lithography machine according to claim 1, characterized in that: The uniform light module also includes a rotating mechanism and a microelectromechanical drive structure. The first integrating bar is mounted on the rotating mechanism to adjust the rotation angle around the optical axis, and the second integrating bar is connected to the microelectromechanical drive structure to adjust the cross-sectional size.

4. The non-imaging lithography illumination system for an i-line lithography machine according to claim 1, characterized in that: According to the target illumination mode, a first control command is sent to the zoom module, and the zoom module is corrected based on the deviation between the actual pupil feature value collected by the pupil monitoring module and the target pupil feature value, until the deviation converges to within the first threshold. After locking the optical parameters of the zoom module, a second control command is sent to the uniformity module. The uniformity index collected by the mask surface monitoring module optimizes the optical parameters of the uniformity module until the uniformity index reaches a second threshold. Based on the effect of adjusting the optical parameters of the uniform light module on the total luminous flux, an adjustment command is simultaneously sent to the light source module to adjust the luminous intensity.

5. The non-imaging lithography illumination system for an i-line lithography machine according to claim 1, characterized in that: The decoupling controller is also used to construct a coupling matrix that characterizes the coupling relationship between the pupil eigenvalues ​​and the uniformity index; Each element of the coupling matrix represents the transfer coefficient of the pupil eigenvalue change to the uniformity index; The decoupling controller updates the coupling matrix based on real-time data from the pupil feature time series and the uniformity feature time series.

6. The non-imaging lithography illumination system for an i-line lithography machine according to claim 5, characterized in that: The decoupling controller also calculates a decoupling index based on historical data of the pupil feature time series and the uniformity feature time series. The decoupling index is used to characterize the degree of influence of pupil changes on uniformity. When the decoupling index exceeds a threshold, a system maintenance prompt is triggered.

7. The non-imaging lithography illumination system for an i-line lithography machine according to claim 6, characterized in that: The method for calculating the decoupling degree index by the decoupling controller is as follows: Select the pupil feature time series and the uniformity feature time series within a preset historical time period, and perform multi-scale wavelet decomposition on both to obtain their respective wavelet coefficients in different frequency bands; Calculate the cross-correlation coefficients of wavelet coefficients in each frequency band to form a cross-correlation coefficient sequence; The decoupling index is obtained by weighting the cross-correlation coefficient sequence, where the weight of the high-frequency band is lower than that of the low-frequency band.

8. The non-imaging lithography illumination system for an i-line lithography machine according to claim 7, characterized in that: If the fluctuation range of the instantaneous phase difference time series is less than the preset phase threshold, it is determined that the uniformity degradation is dominated by pupil drift, and the correction circuit of the zoom module is activated. If the fluctuation range of the instantaneous phase difference time series is greater than or equal to the preset phase threshold, it is determined that the uniformity degradation is dominated by the performance drift of the uniform light module, and the correction loop for the uniform light module is activated.

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