Method of lithography compensation and reticle

Abstract

The application provides a photolithography compensation method and a mask. The photolithography compensation method comprises the following steps: providing at least one mask, each of the at least one mask comprises a peripheral region and a pattern region inside the peripheral region, and a detection mark is arranged in the pattern region; measuring the detection mark to obtain a manufacturing error of the at least one mask; determining a compensation amount according to the manufacturing error; and compensating when the at least one mask is exposed according to the compensation amount.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method for photolithography compensation and a photomask. Background Technology

[0002] In semiconductor lithography, overlay accuracy is a key parameter affecting chip performance and yield. Known technologies primarily improve overlay accuracy by enhancing stage motion precision, optimizing lens performance, or employing advanced process control systems. However, these solutions heavily rely on improved hardware precision, resulting in high equipment costs and physical limitations. For field-level overlay errors introduced by variations in the photomask fabrication process, existing technologies lack effective compensation methods, which has become a significant factor restricting further improvements in overlay accuracy. Summary of the Invention

[0003] On the one hand, this application provides a method for photolithographic compensation, characterized by comprising:

[0004] At least one photomask is provided, each of the at least one photomask including a peripheral region and a graphic region located inside the peripheral region, the graphic region being provided with a detection mark;

[0005] The manufacturing error of the at least one photomask is obtained by measuring the detection mark;

[0006] The compensation amount is determined based on the manufacturing error.

[0007] The compensation is performed when the at least one photomask is exposed, according to the compensation amount.

[0008] In some embodiments, the graphic region includes multiple sub-regions, and the detection mark is provided in each of the sub-regions;

[0009] The detection marks within each sub-region are measured separately to obtain the manufacturing error corresponding to each sub-region;

[0010] The compensation amount for each sub-region is determined based on the manufacturing error corresponding to each sub-region.

[0011] In some embodiments, the patterned region includes a chip patterned region and a kerf patterned region surrounding the chip patterned region, and the detection mark is disposed in the chip patterned region and / or the kerf patterned region.

[0012] In some embodiments, the at least one photomask includes a first photomask and a second photomask having an overlay relationship, and the detection mark includes a first detection mark disposed in the graphic area of ​​the first photomask and a second detection mark disposed in the graphic area of ​​the second photomask;

[0013] Measuring the detection mark to obtain the manufacturing error of the at least one photomask further includes:

[0014] Measure the first detection mark to obtain the first manufacturing error of the first photomask, and measure the second detection mark to obtain the second manufacturing error of the second photomask;

[0015] The step of determining the compensation amount based on the manufacturing error further includes:

[0016] The compensation amount is determined based on the first manufacturing error and the second manufacturing error.

[0017] In some embodiments, determining the compensation amount based on the first manufacturing error and the second manufacturing error further includes:

[0018] The difference between the first manufacturing error and the second manufacturing error is used as the compensation amount;

[0019] The step of compensating according to the compensation amount when the at least one photomask is exposed further includes:

[0020] The compensation is performed during exposure using the first or second photomask, based on the compensation amount.

[0021] In some embodiments, determining the compensation amount based on the first manufacturing error and the second manufacturing error further includes:

[0022] The compensation amount includes a first compensation amount and a second compensation amount, wherein the first compensation amount is determined based on the first manufacturing error, and the second compensation amount is determined based on the second manufacturing error;

[0023] The step of compensating according to the compensation amount when the at least one photomask is exposed further includes:

[0024] Compensation is performed when the first photomask is exposed according to the first compensation amount, and compensation is performed when the second photomask is exposed according to the second compensation amount.

[0025] In some embodiments, the position of the first detection mark on the first photomask is the same as the position of the second detection mark on the second photomask.

[0026] On the other hand, this application provides a photomask, comprising:

[0027] The outer area; and

[0028] The graphic area located inside the outer perimeter area contains a chip graphic and detection marks. The detection marks are used to measure the manufacturing error of the photomask.

[0029] In some embodiments, the patterned region includes a chip patterned region and a kerf patterned region surrounding the chip patterned region, and the detection mark is disposed in the chip patterned region and / or the kerf patterned region.

[0030] In some embodiments, the graphic region is divided into multiple sub-regions, and the detection mark is provided in each sub-region. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a photolithographic compensation method provided in an embodiment of this application.

[0032] Figure 2 This is a top view of the photomask provided in an embodiment of this application.

[0033] Explanation of reference numerals in the attached figures:

[0034] 10 - Graphic area; 11 - Chip graphic area; 12 - Cutting track graphic area; 13 - Detection mark; 20 - Peripheral area. Detailed Implementation

[0035] The technical solution of this application will be further described in detail below with reference to the accompanying drawings. The drawings are simplified and use non-precise proportions, and are only used for the purpose of conveniently and clearly illustrating the embodiments of this application.

[0036] It should be noted that, unless otherwise specified or indicated, the terms "first" and "second" in the specification are used only to distinguish between individual components, elements, steps, etc., and are not used to indicate the logical or sequential relationships between individual components, elements, steps, etc.

[0037] It is understood that although preferred embodiments have been disclosed above in this application, these embodiments are not intended to limit this application. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of this application based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application, without departing from the content of the technical solutions of this application, shall still fall within the scope of protection of the technical solutions of this application.

[0038] In semiconductor integrated circuit manufacturing, photolithography is one of the core processes in wafer fabrication. The photolithography process involves coating the wafer surface with photoresist, transferring the design pattern to the photoresist layer using a photomask, and then forming the desired circuit structure through processes such as development and etching. As integrated circuit technology continues to shrink and device feature sizes continue to decrease, higher requirements are placed on the alignment accuracy between different film layers in the photolithography process.

[0039] Overlay accuracy characterizes the horizontal offset between the current lithographic layer pattern and the previous layer pattern. In known technologies, overlay accuracy is typically controlled at both the wafer-level and field-level. Wafer-level overlay accuracy primarily characterizes the overlay error components that vary with position across the entire wafer, with sources including wafer warpage, uneven film stress distribution, and deviations in the lithography stage's motion trajectory. Field-level overlay accuracy, on the other hand, characterizes the recurring overlay error components within each exposure field, primarily sourced from projection mirror image aberration and mask fabrication errors.

[0040] To control overlay accuracy, various technologies have been developed in this field. In wafer-level control, advanced process control systems can automatically update exposure parameters based on the overlay measurement results of the previous batch of wafers to compensate for the impact of process fluctuations. Simultaneously, by designing a high-precision wafer stage mechanical structure and strictly controlling the stage's movement accuracy, wafer-level overlay errors can also be reduced to some extent. In field-level control, for field-level overlay errors caused by projection lens drift or aberrations, compensation is typically achieved through methods such as optimizing lens design and applying more complex lens models for correction. Furthermore, a high-precision photomask stage mechanical structure also helps control the positional accuracy of the photomask during the exposure process.

[0041] However, the aforementioned known solutions still have shortcomings. On the one hand, both improving the stage motion accuracy and optimizing lens performance heavily rely on advancements in machining accuracy and optical component manufacturing levels. This not only leads to a sharp increase in equipment manufacturing costs but also highlights the inherent physical limitations of mechanical and optical systems, making it difficult to infinitely improve accuracy to meet the increasingly stringent overlay precision requirements of advanced processes. On the other hand, there is a lack of effective compensation methods in known technologies for field-level overlay errors introduced by deviations in the photomask manufacturing process. During the photomask manufacturing process, certain manufacturing errors inevitably exist in the internal pattern position. These errors are transferred to the wafer surface along with the photomask pattern during exposure and recur in each exposure field. Due to the lack of effective compensation schemes for this error source, photomask manufacturing errors have become a significant factor restricting further improvements in field-level overlay precision.

[0042] To address the aforementioned problems, this application provides a method for photolithography compensation and a photomask. This method involves setting detection marks within the patterned area of ​​the photomask, measuring these marks to obtain the fabrication error of the photomask, determining the compensation amount based on this error, and then performing compensation during photomask exposure. By actively measuring and compensating for the fabrication error of the photomask itself, this application can further improve field-level overlay accuracy under known hardware conditions, overcoming the limitations of hardware accuracy on overlay accuracy improvement.

[0043] like Figure 1 As shown, the photolithography compensation method provided in this application mainly includes the following steps: providing at least one photomask, which includes a peripheral region and a patterned region located inside the peripheral region, with detection marks provided in the patterned region; measuring the detection marks to obtain the fabrication error of the photomask; determining the compensation amount based on the fabrication error; and compensating during photomask exposure based on the compensation amount. By setting detection marks in the patterned region of the photomask, the pattern position deviation of each region inside the photomask can be accurately measured before or during use, and the obtained fabrication error can be fed back to the parameter settings of the exposure machine in the form of a compensation amount. Compared with known solutions that only average the photomask as a whole, this application can reflect the local fabrication error distribution characteristics inside the photomask in more detail, thereby improving the compensation accuracy.

[0044] The following will be combined with the appendix Figure 1 and Figure 2 The technical solution of this application is described in detail. Figure 1 This is a flowchart illustrating a photolithographic compensation method provided in an embodiment of this application. Figure 2 This is a top view of the photomask provided in an embodiment of this application. It should be noted that the following embodiments are merely preferred implementations of this application and do not constitute a limitation on the scope of protection of this application.

[0045] In this application, manufacturing error refers to the spatial deviation of the actual position of the detection mark within the patterned area of ​​the photomask after manufacturing, relative to the ideal design position of the detection mark. This manufacturing error is a vector, possessing both magnitude and direction, and can comprehensively reflect the offset characteristics of the patterned position during the photomask manufacturing process.

[0046] Specifically, manufacturing errors include the following components:

[0047] First, the translation error in the X and Y directions. The X-direction translation error, denoted as Tx, is the linear offset of the actual position of the detection mark relative to its ideal design position in the X direction, measured in units of length (e.g., nanometers, nm). The Y-direction translation error, denoted as Ty, is the linear offset of the actual position of the detection mark relative to its ideal design position in the Y direction, measured in units of length (e.g., nanometers, nm). Tx and Ty together constitute the translation error vector in a two-dimensional plane, characterizing the overall displacement of the photomask pattern in the horizontal plane.

[0048] Second, scaling error. Scaling error refers to the proportion by which the overall size of the photomask pattern is magnified or reduced relative to the design size, denoted as Ms, and measured in parts per million (ppm). Scaling error can be non-uniform, meaning the scaling errors in the X and Y directions can be different, denoted as Ms_X and Ms_Y respectively. Scaling error reflects the changes in pattern size caused by material shrinkage or expansion, or deviations in the projection magnification of the exposure equipment, during the photomask fabrication process.

[0049] Third, rotational error. Rotational error refers to the angular displacement of the entire photomask pattern around its center or reference point, denoted as Rs, and measured in degrees (°) or radians (rad). Rotational error reflects the overall tilt of the pattern caused by the torsion of the photomask substrate during exposure or etching, or by the rotational deviation of the photomask fabrication equipment itself.

[0050] Manufacturing errors can also include higher-order error components, such as trapezoidal distortion (the image exhibits trapezoidal deformation in the X or Y direction), barrel distortion (the edges of the image bend inward), and pincushion distortion (the edges of the image bend outward). Higher-order error components are typically obtained by using error data from multiple detection markers through polynomial fitting or model fitting.

[0051] Since manufacturing errors are vectors, the manufacturing errors at multiple detection marker locations can form an error vector field, describing the error distribution characteristics at each location within the photomask pattern area. This error vector field reflects both the magnitude and direction of the error at each location, providing a complete data foundation for subsequent zonal compensation.

[0052] Taking a specific numerical example, if the standard position coordinates of a certain detection mark are (10.000mm, 10.000mm), and the actual measured position coordinates are (10.001mm, 9.999mm), then the manufacturing error vector at the location of the detection mark is (+1nm, -1nm). Here, +1nm represents the actual position being offset by 1nm in the positive X direction relative to the standard position, and -1nm represents the actual position being offset by 1nm in the negative Y direction relative to the standard position. The direction of this error vector is the vector direction from the standard position to the actual position, i.e., the lower right. The magnitude of this error vector is... The direction and magnitude of this error vector can fully describe the manufacturing error characteristics at the detection mark location. Similarly, the error vectors from multiple detection mark locations can fully describe the error distribution characteristics within the photomask pattern area.

[0053] In this application, the compensation amount is a vector, possessing both magnitude and direction. The magnitude of the compensation amount is determined based on the magnitude of the manufacturing error, and the direction of the compensation amount is opposite to the direction of the manufacturing error to counteract the influence of the manufacturing error on exposure accuracy. Specifically, if the manufacturing error at a certain detection mark position is (ΔX, ΔY), then its corresponding compensation amount is (-ΔX, -ΔY), meaning that the components of the compensation amount in the X and Y directions are the opposites of the components of the manufacturing error in the corresponding directions. For angular errors, if the manufacturing error includes an angular deviation Δθ, then the corresponding angular compensation amount is -Δθ.

[0054] After obtaining the fabrication error vectors at each detection mark position on the photomask, these discrete error vector data need to be converted into compensation parameters usable during exposure. The method for determining the compensation amount varies depending on the application scenario and compensation strategy.

[0055] As a vector, the directionality of the compensation amount is reflected when it is applied to the machine parameters. The direction of the translational compensation amount is determined by the displacement of the workpiece stage in the X and Y directions. A negative compensation amount indicates movement of the workpiece stage in the negative direction of the coordinate axis; a positive compensation amount indicates movement in the positive direction of the coordinate axis. The direction of the rotational compensation amount is determined by the rotation of the workpiece stage around the vertical axis. A negative rotational compensation amount indicates counter-clockwise rotation; a positive value indicates clockwise rotation. The direction of the scaling compensation amount is determined by increasing or decreasing the projection magnification. A negative scaling compensation amount indicates decreasing the projection magnification; a positive value indicates increasing the projection magnification. When the compensation amount is applied to the machine, its magnitude and sign jointly determine the amplitude and direction of the adjustment performed by the machine. If the compensation amount is represented only as an absolute value without directional information, the machine cannot determine the direction of the adjustment. Therefore, the compensation amount must be provided as a vector with a sign, or as an absolute value combined with an independent direction indicator parameter. In the subprogram, the compensation amount is usually written in the form of a signed numerical value. The machine automatically determines the adjustment direction based on the sign of the value and determines the adjustment range based on the absolute value of the value.

[0056] Example 1

[0057] This embodiment describes a method for measuring and compensating for manufacturing errors of a single photomask, applicable to precision control scenarios for independent photomasks.

[0058] The method in this embodiment includes the following steps:

[0059] Step S1, providing at least one photomask, each of the at least one photomask including a peripheral region and a graphic region located inside the peripheral region, the graphic region being provided with a detection mark.

[0060] Combination Figure 2 As shown, the photomask includes a peripheral region 20 and a patterned region 10 located inside the peripheral region 20. The peripheral region 20 typically has photomask alignment marks for the lithography machine to perform initial alignment between the photomask and the wafer. The patterned region 10 is the main functional area of ​​the photomask, and it includes multiple sub-regions, each with a detection mark 13. In some embodiments, the patterned region 10 contains a chip patterned region 11 and a dicing patterned region 12. The chip patterned region 11 corresponds to the circuit pattern of each chip cell on the wafer, and the dicing patterned region 12 surrounds the chip patterned region and is located in the gap between adjacent chip patterned regions for subsequent dicing processes. Detection marks 13 are also provided within the patterned region 10. The detection marks 13 are used to measure the positional deviation of the internal pattern of the photomask after fabrication. The detection mark 13 can be set in the dicing pattern area 12 within the pattern area 10, or in the chip pattern area 11, or simultaneously in both areas, i.e., the detection mark 13 is set in the dicing pattern area 12 and / or the chip pattern area 11 within the pattern area 10. Setting the detection mark 13 within the pattern area 10, rather than limiting it to the outer periphery of the photomask, can more directly reflect the fabrication error of the actual pattern area inside the photomask. Since the detection mark 13 and the chip pattern on the photomask are formed simultaneously in the same photomask fabrication process, the positional deviation of the detection mark 13 can effectively characterize the fabrication error of the chip pattern. The detection mark 13 can be implemented in various graphic forms, such as a spiral mark, a bar mark, an X-shaped mark, a cross-shaped mark, a mark composed of inclined lines, or a long strip mark composed of block-shaped graphics, as long as the mark's positional information can be read by a measuring device. This step, by setting the detection mark within the pattern area of ​​the photomask, provides the necessary physical basis for subsequent measurement of photomask fabrication errors.

[0061] Step S2: Measure the detection mark to obtain the manufacturing error of the at least one photomask.

[0062] In this step, the aforementioned detection mark 13 is measured to obtain the fabrication error of the photomask. Further, the detection mark 13 in each sub-region is measured separately to obtain the corresponding fabrication error for each sub-region. In specific operation, optical measurement equipment or electron beam measurement equipment can be used to read the actual position coordinates of the detection mark 13 on the photomask, and then these actual position coordinates are compared with the standard position coordinates of the mark in the design layout to calculate the deviation between the two. This deviation is the fabrication error of the photomask at the mark position. This fabrication error can include X-direction translation error and Y-direction translation error, representing the offset of the actual position of the detection mark in the X and Y directions relative to the standard position, respectively.

[0063] Specifically, if the standard position coordinates of a detection mark are (X_standard, Y_standard), and the actual measured position coordinates are (X_actual, Y_actual), then the manufacturing error at the position of the detection mark can be expressed as (X_actual - X_standard, Y_actual - Y_standard). Wherein, the manufacturing error in the X direction is X_actual - X_standard, and the manufacturing error in the Y direction is Y_actual - Y_standard. If X_actual - X_standard is positive, it indicates that the actual position of the detection mark is offset in the positive X direction relative to the standard position; if it is negative, it indicates an offset in the negative X direction. Similarly, the positive or negative value of the manufacturing error in the Y direction indicates an offset in the positive or negative Y direction.

[0064] By measuring multiple detection marks 13 distributed at different locations within the graphic area, the spatial distribution information of the mask manufacturing error can be obtained. Let the standard position coordinates of the i-th detection mark be (X_i, Y_i), and the actual measured position coordinates be (X_i', Y_i'). Then, the manufacturing error at this mark location is (ΔX_i, ΔY_i) = (X_i' - X_i, Y_i' - Y_i). The manufacturing errors at each mark location collectively constitute the manufacturing error of the mask, fully describing the magnitude and direction of the manufacturing error at each location within the mask graphic area.

[0065] In practice, four detection marks can be selected within the graphic area of ​​the photomask, with standard position coordinates of A(0,0), B(10,0), C(10,10), and D(0,10), in mm. The actual position coordinates are measured as A1(0.001,0.001), B1(10.002,-0.001), C1(10.001,10.002), and D1(-0.001,9.998). By comparing the deviations between the actual and standard positions, the manufacturing error at each mark can be obtained. The manufacturing error at mark A is (+1nm, +1nm), indicating that the actual position of mark A is offset by 1nm in the positive X direction and 1nm in the positive Y direction relative to the standard position. The manufacturing error at mark B is (+2nm, -1nm), indicating that the actual position of mark B is offset by 2nm in the positive X direction and 1nm in the negative Y direction relative to the standard position. The fabrication error at marker C is (+1nm, +2nm), meaning that the actual position of marker C is offset by 1nm in the positive X direction and 2nm in the positive Y direction. The fabrication error at marker D is (-1nm, -2nm), meaning that the actual position of marker D is offset by 1nm in the negative X direction and 2nm in the negative Y direction.

[0066] For the measurement data of multiple detection marks 13 within the photomask, the relative positional relationships between each mark can be further calculated to determine higher-order fabrication errors. For example, the standard distance in the X direction between A and B is 10 mm, while the actual distance is 10.001 mm, a deviation of +1 nm, indicating that there may be local scaling errors in this area. The diagonal direction between B and D can also be used to determine rotational errors. By analyzing the changes in the relative positions between each mark point, the spatial distribution characteristics of photomask fabrication errors can be evaluated more comprehensively.

[0067] In addition, manufacturing errors also include angular errors. For certain detection marks 13 that require angular deviation measurement, such as marks composed of inclined lines or X-shaped marks, the angular error can be obtained by measuring the inclination angle of the lines. Specifically, if the designed angle of a certain inclined line is θ_standard and the actual measured angle is θ_actual, then the angular error at the location of the detection mark is θ_actual - θ_standard. This angular error can be included in the rotational error component Rs, or recorded and compensated as an independent angular error.

[0068] The above measurement method can be used to obtain the manufacturing errors at each detection mark position on the photomask. These manufacturing errors can include translational errors in the X and Y directions, as well as angular errors. These error vectors constitute a complete data set of photomask manufacturing errors, providing accurate input for determining subsequent compensation amounts.

[0069] Step S3: Determine the compensation amount based on the manufacturing error. Further, determine the compensation amount for each sub-region based on the manufacturing error corresponding to each sub-region.

[0070] In this step, the compensation amount is a vector with magnitude and direction. The magnitude of the compensation amount is determined based on the magnitude of the manufacturing error, and the direction of the compensation amount is opposite to the direction of the manufacturing error to counteract the impact of the manufacturing error on exposure accuracy. Specifically, if the manufacturing error at a certain detection mark position is (ΔX, ΔY), then its corresponding compensation amount is (-ΔX, -ΔY), meaning that the components of the compensation amount in the X and Y directions are the opposites of the components of the manufacturing error in the corresponding directions. For angular errors, if the manufacturing error includes an angular deviation Δθ, then the corresponding angular compensation amount is -Δθ.

[0071] In the single-layer photomask error measurement and compensation scenario of this embodiment, the compensation amount is determined based on the manufacturing error of the single photomask itself. Specifically, based on the manufacturing error data at each detection mark position on the photomask, the translation error (Tx, Ty), scaling error Ms (which can be decomposed into Ms_X and Ms_Y), and rotation error Rs of the photomask are solved by model fitting. Then, the negative value of each error component is taken as the corresponding compensation amount. For example, if the fitted photomask has a translation error of (Tx=+1.0nm, Ty=+0.5nm), a scaling error of Ms_X=+100ppm, Ms_Y=-300ppm, and a rotation error of Rs=+0.006°, then the corresponding compensation amounts are: translation compensation amount is (-1.0nm, -0.5nm), scaling compensation amount is Ms_X_comp=-100ppm, Ms_Y_comp=+300ppm, and rotation compensation amount is Rs_comp=-0.006°. When exposing the photomask, the aforementioned compensation amount is loaded into the machine parameters, and the machine performs corresponding reverse adjustments based on the direction and magnitude of the compensation amount.

[0072] After obtaining the fabrication errors at each detection mark position on the photomask, these discrete error data need to be converted into compensation parameters usable during exposure. For translation errors, the compensation amount can be directly taken as the translation amount opposite to the direction of the fabrication error. For example, if the fabrication error in a certain region is +1nm in the X direction, then the Tx compensation amount for that region is -1nm; if the fabrication error in the Y direction is +2nm, then the Ty compensation amount is -2nm. Since the fabrication error is a vector, the compensation amount is also a vector, its direction is opposite to the error direction, and its magnitude is equal to the magnitude of the fabrication error.

[0073] The scaling error Ms represents the ratio of the overall size of the photomask pattern to the design size. Taking the above four-mark measurement data as an example, based on the actual position coordinates of the four detection marks, the average spacing of the actual pattern in the X direction is 10.001 mm, and the average spacing in the Y direction is 9.997 mm, while the design spacing is 10.000 mm. Therefore, the scaling error Ms_X in the X direction is +100 ppm (i.e., (10.001 - 10.000) / 10.000 × 10^6), and the scaling error Ms_Y in the Y direction is -300 ppm (i.e., (9.997 - 10.000) / 10.000 × 10^6). Correspondingly, the scaling compensation amount in the X direction is -100 ppm, and the scaling compensation amount in the Y direction is +300 ppm.

[0074] The rotation error Rs represents the angular displacement of the entire photomask pattern around its center. The rotation error can be calculated by comparing the deviations along the diagonal. Ideally, the slope of the AC line should be 1, while the actual slope of the A1-C1 line is (10.002-0.001) / (10.001-0.001) = 10.001 / 10.000 = 1.0001, corresponding to an angular deviation of approximately 0.006°. Therefore, the rotation error Rs is approximately +0.006°, and the corresponding rotation compensation is -0.006°.

[0075] For higher-order error components, such as trapezoidal distortion or barrel distortion, the corresponding compensation parameters need to be calculated through model fitting based on the error vector data of multiple detection marks. Specifically, an error model including translation, scaling, rotation, and higher-order distortion parameters can be established, and the optimal values ​​of each parameter can be solved using fitting algorithms such as the least squares method to obtain the corresponding compensation amount. The fitted model parameters can be directly used as compensation parameters for the exposure machine. For a photomask with simultaneous translation, scaling, and rotation errors, the following error model can be established:

[0076] X_error = Tx + Ms × X_standard - Rs × Y_standard;

[0077] Y_error = Ty + Rs × X_standard + Ms × Y_standard;

[0078] Here, X_error and Y_error represent the fabrication errors of the detection markers in the X and Y directions, respectively, while X_standard and Y_standard represent the standard position coordinates of the detection markers. Using the measurement data of these four markers, the optimal values ​​of the four parameters Tx, Ty, Ms, and Rs can be obtained by substituting them into the error model and performing least-squares fitting. The fitted parameters are the quantitative representation of the mask fabrication error. If it is necessary to compensate for higher-order distortion errors simultaneously, higher-order terms can be added to the above model, such as adding quadratic distortion terms in the X and Y directions, to achieve more accurate compensation.

[0079] When determining the compensation amount, the compensation capability of the lithography machine must also be considered. The compensation amount must be converted into a parameter format that the machine can recognize, such as a workpiece stage displacement correction value or a scanning direction correction value. The purpose of this step is to convert the manufacturing error obtained from measurement into an executable compensation instruction.

[0080] Step S4: Compensate according to the compensation amount when the at least one photomask is exposed.

[0081] In this step, compensation is performed during photomask exposure based on the aforementioned compensation amount. In practice, the compensation amount is typically loaded into the machine's control parameters via a subprogram. The subprogram is a set of preset instruction sequences executable by the machine, used to dynamically adjust the machine's control parameters during exposure. Before the photomask is used, the compensation parameters, converted from the photomask fabrication error measured using inspection marks, are written into the subprogram. During the actual exposure, the machine automatically calls this subprogram and adjusts parameters such as the workpiece stage position and scanning direction in real time according to the preset compensation parameters.

[0082] For example, if the compensation amount for a certain area indicates that the stage needs to move -1nm in the X direction, the machine will automatically perform this displacement correction when exposing that area, thereby making the position of the pattern transferred to the wafer surface closer to the standard position. If the compensation amount includes a scaling compensation of -100ppm, the machine will adjust the projection magnification or scanning speed accordingly during exposure to restore the size of the pattern transferred to the wafer to the design value. If the compensation amount includes a rotation compensation of -0.006°, the machine will control the stage to rotate counterclockwise by 0.006° around the vertical axis during exposure to compensate for the rotational error of the photomask itself. By performing the corresponding compensation operation area by area throughout the exposure process, the influence of photomask fabrication errors on the position of the pattern on the wafer can be eliminated. The purpose of this step is to actually apply the compensation amount during the exposure process to achieve effective correction of photomask fabrication errors.

[0083] In practical implementation, the patterned area 10 of the photomask can be further divided into multiple sub-regions. For example, based on the number of rows and columns of chips on the photomask, the patterned area 10 can be divided into m×n sub-regions, where m and n are both positive integers. Each sub-region is equipped with a detection mark 13. By measuring the detection mark 13 in each sub-region, the manufacturing error corresponding to each sub-region can be obtained, and the compensation vector corresponding to each sub-region can be determined. Using partitioned measurement and partitioned compensation allows for a more precise description of the non-uniform spatial distribution characteristics of the photomask manufacturing error. The manufacturing errors in the center and edge regions of the photomask may differ significantly; partitioned compensation allows for the application of different compensation amounts to different regions, thereby improving the targeting and effectiveness of the compensation. During exposure, the light source can sequentially illuminate each sub-region on the photomask (e.g., by moving the photomask to bring the corresponding sub-region into the field of view of the light source). Exposure operations can then be performed based on multiple sub-regions, and the machine can call the corresponding compensation parameters according to the current position of the exposed area to achieve differentiated compensation for different regions.

[0084] Taking the photomask pattern area as an example, which is divided into 9 sub-regions of 3×3, the sub-regions are denoted as (row 1 column 1), (row 1 column 2), (row 1 column 3), (row 2 column 1), (row 2 column 2), (row 2 column 3), (row 3 column 1), (row 3 column 2), and (row 3 column 3). After measuring the detection marks of each sub-region, the manufacturing errors such as Tx, Ty, Ms, and Rs of each sub-region are obtained. Specifically, the Tx errors of the three sub-regions in the left column (row 1, column 1, row 2, column 1, row 3, column 1) are +2nm, +1.8nm, and +2.1nm, respectively; the Tx errors of the three sub-regions in the middle column (row 1, column 2, row 2, column 2, row 3, column 2) are +0.5nm, +0.3nm, and +0.6nm, respectively; and the Tx errors of the three sub-regions in the right column (row 1, column 3, row 2, column 3, row 3, column 3) are -1.5nm, -1.3nm, and -1.6nm, respectively. Correspondingly, the Tx compensation amounts for each sub-region in the left column are -2nm, -1.8nm, and -2.1nm; for the three sub-regions in the middle column, they are -0.5nm, -0.3nm, and -0.6nm; and for the three sub-regions in the right column, they are +1.5nm, +1.3nm, and +1.6nm. The data above shows that the Tx errors of the three sub-regions in the left column of the photomask are all positive, meaning the actual position is offset in the positive X direction relative to the standard position; the Tx errors of the three sub-regions in the right column are all negative, meaning the actual position is offset in the negative X direction relative to the standard position; and the Tx error of the middle column is close to zero. This spatial distribution characteristic indicates that the photomask has significant edge region errors in the X direction. During exposure, when the exposure position is in the three sub-regions in the left column, the machine uses the corresponding negative translation compensation; when the exposure position is in the three sub-regions in the middle column, the machine uses a smaller compensation amount; and when the exposure position is in the three sub-regions in the right column, the machine uses positive translation compensation. This differentiated compensation by region can effectively correct the spatial non-uniform distribution of photomask fabrication errors. If only a single compensation amount is used to uniformly compensate the entire photomask, it is impossible to simultaneously meet the different compensation requirements of the three sub-regions in the left and right columns, resulting in overcompensation or undercompensation in some areas, and the overlay accuracy cannot reach the optimal level.

[0085] This embodiment obtains the fabrication error of the photomask by measuring the detection marks within the patterned area of ​​the photomask and compensates for this error during the exposure process. This effectively eliminates the pattern position deviation introduced by the photomask fabrication process itself, thereby improving the field-level overlay accuracy. Compared with solutions that rely solely on improving mechanical motion accuracy or optical performance, this embodiment achieves further accuracy improvement at a lower cost through software compensation.

[0086] Example 2

[0087] This embodiment describes a method for independently compensating two photomasks that have an overlay correspondence.

[0088] In semiconductor photolithography, certain critical film layers have an overlay relationship. For example, a device structure needs to be formed by exposing a first photomask and a second photomask separately, and the two patterns are finally superimposed on the wafer to form a complete device structure. To ensure device performance, the relative positions between the two patterns must meet strict overlay accuracy requirements. This embodiment, based on Embodiment 1, further provides a processing method for two photomasks with an overlay relationship.

[0089] In this embodiment, based on step S1 of embodiment one, a first photomask and a second photomask with an overlay correspondence are provided. The first and second photomasks each include a peripheral region and a patterned region located inside the peripheral region. A first detection mark is provided within the patterned region of the first photomask, and a second detection mark is provided within the patterned region of the second photomask. Preferably, the positions of the first detection mark on the first photomask and the second detection mark on the second photomask are the same; that is, during photomask layout design, the two photomasks have detection marks with the same positional coordinates in corresponding areas. The advantage of this is that when the two photomasks are subjected to error measurement, the measurement data can be directly compared based on the same positional coordinates, facilitating the subsequent calculation of compensation amounts.

[0090] Based on step S2 of Embodiment 1, the first detection mark is measured to obtain the first manufacturing error of the first photomask, and the second detection mark is measured to obtain the second manufacturing error of the second photomask. Specifically, by measuring the deviation between the actual position and the standard position of the first detection mark, the first manufacturing error (ΔX_1, ΔY_1) of the first photomask in the X and Y directions is obtained; by measuring the deviation between the actual position and the standard position of the second detection mark, the second manufacturing error (ΔX_2, ΔY_2) of the second photomask in the X and Y directions is obtained. The specific measurement operation is the same as in Embodiment 1, that is, the actual position coordinates of the detection mark are read using a measuring device, and then compared with the standard position coordinates to calculate the deviation vector. For each photomask, the actual positions of multiple detection marks within its graphic area can be measured to obtain the manufacturing error data corresponding to each area.

[0091] Based on step S3 of Embodiment 1, a first compensation amount is determined according to a first manufacturing error, and a second compensation amount is determined according to a second manufacturing error. In the independent compensation method of this embodiment, the determination of the first compensation amount depends only on the first manufacturing error of the first photomask itself, and its goal is to make the pattern of the first photomask as close as possible to the standard position during exposure; the determination of the second compensation amount depends only on the second manufacturing error of the second photomask itself, and its goal is to make the pattern of the second photomask as close as possible to the standard position during exposure. That is to say, the two photomasks are compensated independently according to their respective compensation amounts, and each moves closer to the standard position.

[0092] In one specific embodiment, the first detection mark on the first photomask is measured to obtain a first manufacturing error (+1.0 nm, +0.5 nm) relative to a standard position. Based on the first manufacturing error, a first compensation amount is determined to be (-1.0 nm, -0.5 nm), causing the first photomask to move closer to the standard position during exposure. The second detection mark on the second photomask is measured to obtain a second manufacturing error (+1.1 nm, -0.3 nm) relative to a standard position. Based on the second manufacturing error, a second compensation amount is determined to be (-1.1 nm, +0.3 nm), causing the second photomask to move closer to the standard position during exposure.

[0093] Based on step S4 of Embodiment 1, compensation is performed according to a first compensation amount when exposing the first photomask; and compensation is performed according to a second compensation amount when exposing the second photomask. Through separate compensations, the first fabrication error of the first photomask and the second fabrication error of the second photomask are corrected in their respective exposure steps. The loading and execution method of the compensation amount is the same as in Embodiment 1, that is, the compensation parameters are written into the subprogram of the exposure machine, and automatically called and executed by the machine during exposure.

[0094] In the above specific embodiment, if the first photomask with a first manufacturing error of (+1.0nm, +0.5nm) is compensated by a first compensation vector (-1.0nm, -0.5nm), its actual exposure position is corrected to fluctuate around (0nm, 0nm); if the second photomask with a second manufacturing error of (+1.1nm, -0.3nm) is compensated by a second compensation vector (-1.1nm, +0.3nm), its actual exposure position is corrected to fluctuate around (0nm, 0nm). Ultimately, the overlay error vector between the first and second photomasks approaches (0, 0).

[0095] The independent compensation method in this embodiment is applicable to situations where the errors of the two photomasks are independent of each other. For example, when the two photomasks come from different photomask manufacturers or use different manufacturing processes, their respective manufacturing error characteristics may differ significantly. In this case, independent compensation can ensure that each photomask achieves a high absolute positional accuracy.

[0096] Example 3

[0097] This embodiment describes a method for differential compensation of two photomasks that have an overlay correspondence.

[0098] In this embodiment, based on step S1 of Embodiment 1, a first photomask and a second photomask with an overlay correspondence are provided. The first and second photomasks each include a peripheral region and a patterned region located inside the peripheral region. A first detection mark is provided within the patterned region of the first photomask, and a second detection mark is provided within the patterned region of the second photomask. The first and second detection marks are respectively located at the same positions on the first and second photomasks to facilitate spatial correspondence and comparison of error data between the two photomasks.

[0099] Based on step S2 of Embodiment 1, the first detection mark is measured to obtain the first manufacturing error of the first photomask; the second detection mark is measured to obtain the second manufacturing error of the second photomask. Specifically, the first manufacturing error of the first photomask is obtained by measuring the deviation between the actual position and the standard position of the first detection mark; the second manufacturing error of the second photomask is obtained by measuring the deviation between the actual position and the standard position of the second detection mark. The first and second manufacturing errors are vectors, including X-direction components and Y-direction components. The positive and negative signs of the first and second manufacturing errors indicate the offset direction.

[0100] Specifically, if the standard position coordinates of the first detection mark on the first photomask are (X_standard, Y_standard), and the actual measured position coordinates are (X_1_actual, Y_1_actual), then the first manufacturing error is (ΔX_1, ΔY_1) = (X_1_actual - X_standard, Y_1_actual - Y_standard). If ΔX_1 is positive, it indicates that the actual position of the first photomask is offset in the positive X direction relative to the standard position; if it is negative, it indicates an offset in the negative X direction. Similarly, the sign of ΔY_1 indicates the offset direction in the Y direction.

[0101] If the standard position coordinates of the second detection mark on the second photomask are also (X_standard, Y_standard), and the actual measured position coordinates are (X_2_actual, Y_2_actual), then the second manufacturing error is (ΔX_2, ΔY_2) = (X_2_actual - X_standard, Y_2_actual - Y_standard). If ΔX_2 is positive, it indicates that the actual position of the second photomask is offset in the positive X direction relative to the standard position; if it is negative, it indicates an offset in the negative X direction. Similarly, the sign of ΔY_2 indicates the offset direction in the Y direction.

[0102] Based on step S3 of Embodiment 1, a compensation amount is determined according to the first manufacturing error and the second manufacturing error. In this embodiment, the method for determining the compensation amount differs from that of Embodiment 2. Specifically, the difference between the first manufacturing error and the second manufacturing error is used as the compensation amount. Let the first manufacturing error at the position of the first detection mark on the first photomask be (ΔX_1, ΔY_1), and the second manufacturing error at the position of the second detection mark on the second photomask be (ΔX_2, ΔY_2), then the compensation amount is (ΔX_1 - ΔX_2, ΔY_1 - ΔY_2).

[0103] The principle of this differential compensation method is as follows: For two photomasks with an overlay correspondence, if the two photomasks are compensated independently (i.e., in Example 2), the compensation amount for the first photomask is (-ΔX_1, -ΔY_1), and the compensation amount for the second photomask is (-ΔX_2, -ΔY_2). In this case, the overlay error between the two photomasks depends on the manufacturing errors of each photomask. However, by using the differential compensation method, with the difference between the first and second manufacturing errors as the compensation amount, the relative deviation between the two photomasks can be eliminated more directly, rather than eliminating their absolute deviations relative to the standard position.

[0104] In one specific embodiment, if the first detection mark in a certain area of ​​the first photomask measures a first manufacturing error (ΔX_1, ΔY_1) = (+1.0nm, +0.5nm), it indicates that the actual position of the first photomask is offset by 1.0nm in the positive X direction and 0.5nm in the positive Y direction relative to the standard position. If the second detection mark in the corresponding area of ​​the second photomask measures a second manufacturing error (ΔX_2, ΔY_2) = (+1.1nm, -0.3nm), it indicates that the actual position of the second photomask is offset by 1.1nm in the positive X direction and 0.3nm in the negative Y direction relative to the standard position. Then the compensation amount is (ΔX_1 - ΔX_2, ΔY_1 - ΔY_2) = (+1.0nm - 1.1nm, +0.5nm - (-0.3nm)) = (-0.1nm, +0.8nm). This compensation amount indicates that the second photomask is offset 0.1nm to the left in the X direction and 0.8nm upward in the Y direction relative to the first photomask.

[0105] Based on step S4 of Embodiment 1, compensation is performed during exposure of the first or second photomask according to the aforementioned compensation amount. Specifically, it is possible to use the first photomask as a reference and apply the aforementioned compensation amount when exposing the second photomask, so that the exposure position of the second photomask approaches the actual position of the first photomask; alternatively, it is possible to use the second photomask as a reference and apply the aforementioned compensation amount when exposing the first photomask. Regardless of which method is chosen, the purpose is to eliminate the relative positional deviation between the two photomasks.

[0106] If compensation is chosen to be performed during the exposure of the second photomask, the compensation amount for the second photomask is (-0.1nm, +0.8nm). This compensation means that during exposure, the stage of the second photomask needs to move 0.1nm in the negative X direction and 0.8nm in the positive Y direction. After this compensation, the actual exposure position deviation of the second photomask is corrected from (+1.1nm, -0.3nm) to (+1.1nm - 0.1nm, -0.3nm + 0.8nm) = (+1.0nm, +0.5nm), which is consistent with the fabrication error vector of the first photomask (+1.0nm, +0.5nm). At this point, the relative deviation between the two photomasks is zero, and the overlay error is ideally zero.

[0107] This differential compensation method differs fundamentally from the independent compensation method in Example 2. In the independent compensation method of Example 2, the first compensation amount is (-1.0nm, -0.5nm), and the second compensation amount is (-1.1nm, +0.3nm). After independent compensation, the actual exposure position of the first photomask is corrected to (0nm, 0nm), and the actual exposure position of the second photomask is corrected to (0nm, 0nm). The absolute positions of both photomasks are close to the standard positions, but the required compensation amounts are (-1.0nm, -0.5nm) and (-1.1nm, +0.3nm), respectively. In contrast, in the differential compensation method of this example, only a compensation amount of (-0.1nm, +0.8nm) needs to be applied when exposing the second photomask to make the relative deviation between the two photomasks zero. The two compensation methods differ in the calculation method of the compensation amount, the timing of application, and the technical effect: independent compensation makes each layer approach the standard position, while differential compensation aligns the two layers together.

[0108] The differential compensation method in this embodiment is particularly suitable for scenarios where the manufacturing errors of two photomasks have similar characteristics, such as when the two photomasks are manufactured by the same manufacturer using the same process, or when there is a systematic correlation between the manufacturing errors of the two photomasks. In this case, the difference in the actual positional deviation of the two photomasks can effectively reflect the relative deviation between the two layers, thereby achieving ideal overlay accuracy through a single compensation.

[0109] In summary, the lithography compensation method and photomask provided in the embodiments of this application obtain the fabrication error of the photomask by setting detection marks within the patterned area of ​​the photomask and measuring the deviation of the actual position of the detection marks relative to the standard position. Depending on different application scenarios, appropriate compensation strategies can be flexibly selected: for independent use of a single photomask, the compensation amount is directly determined and compensation is performed based on the fabrication error of the photomask; for a first photomask and a second photomask with an overlay correspondence, if the fabrication errors of the first and second photomasks are independent and both need to be corrected to the standard position, an independent compensation method can be adopted, determining and compensating for their respective compensation amounts based on the fabrication errors of the first and second photomasks; if the fabrication errors of the first and second photomasks have similar characteristics and the main goal is to eliminate interlayer relative deviations, a difference compensation method can be adopted, using the difference between the fabrication errors of the first and second photomasks as the compensation amount, and compensation is performed when one of the photomasks is exposed.

[0110] Through the above methods, this application can effectively eliminate the pattern position deviation introduced by the photomask fabrication process itself, and improve the field-level overlay accuracy. In each embodiment, the application of compensation is achieved through a subprogram of the exposure machine. The machine performs corresponding adjustments according to the direction and magnitude of the compensation, thereby accurately transferring the photomask pattern to the target position on the wafer surface. The technical solutions of the above embodiments can be combined with each other or implemented individually according to actual process requirements, without departing from the protection scope of this application.

Claims

1. A method of lithography compensation, characterized by, include: At least one photomask is provided, each of the at least one photomask including a peripheral region and a graphic region located inside the peripheral region, the graphic region being provided with a detection mark; The manufacturing error of the at least one photomask is obtained by measuring the detection mark; The compensation amount is determined based on the manufacturing error. The compensation is performed when the at least one photomask is exposed, according to the compensation amount.

2. The photolithographic compensation method according to claim 1, characterized in that, The graphic region includes multiple sub-regions, and the detection mark is provided in each sub-region. The detection marks within each sub-region are measured separately to obtain the manufacturing error corresponding to each sub-region; The compensation amount for each sub-region is determined based on the manufacturing error corresponding to each sub-region.

3. The photolithographic compensation method according to claim 1, characterized in that, The patterned area includes a chip patterned area and a kerf patterned area surrounding the chip patterned area, and the detection mark is disposed in the chip patterned area and / or the kerf patterned area.

4. The photolithographic compensation method according to any one of claims 1-3, characterized in that, The at least one photomask includes a first photomask and a second photomask having an overlay relationship, and the detection mark includes a first detection mark disposed in the graphic area of ​​the first photomask and a second detection mark disposed in the graphic area of ​​the second photomask; Measuring the detection mark to obtain the manufacturing error of the at least one photomask further includes: Measure the first detection mark to obtain the first manufacturing error of the first photomask, and measure the second detection mark to obtain the second manufacturing error of the second photomask; The step of determining the compensation amount based on the manufacturing error further includes: The compensation amount is determined based on the first manufacturing error and the second manufacturing error.

5. The photolithographic compensation method according to claim 4, characterized in that, Determining the compensation amount based on the first manufacturing error and the second manufacturing error further includes: The difference between the first manufacturing error and the second manufacturing error is used as the compensation amount; The step of compensating according to the compensation amount when the at least one photomask is exposed further includes: The compensation is performed during exposure using the first or second photomask, based on the compensation amount.

6. The photolithographic compensation method according to claim 4, characterized in that, Determining the compensation amount based on the first manufacturing error and the second manufacturing error further includes: The compensation amount includes a first compensation amount and a second compensation amount, wherein the first compensation amount is determined based on the first manufacturing error, and the second compensation amount is determined based on the second manufacturing error; The step of compensating according to the compensation amount when the at least one photomask is exposed further includes: Compensation is performed when the first photomask is exposed according to the first compensation amount, and compensation is performed when the second photomask is exposed according to the second compensation amount.

7. The method for improving photolithographic alignment accuracy according to claim 4, characterized in that, The position of the first detection mark on the first photomask is the same as the position of the second detection mark on the second photomask.

8. A photomask, characterized in that, include: Outer area; as well as The graphic area located inside the outer perimeter area contains a chip graphic and detection marks. The detection marks are used to measure the manufacturing error of the photomask.

9. The photomask according to claim 8, characterized in that, The pattern area includes a chip pattern area and a kerf pattern area surrounding the chip pattern area, and the detection mark is disposed in the chip pattern area and / or the kerf pattern area.

10. The photomask according to claim 8 or 9, characterized in that, The graphic area is divided into multiple sub-regions, and each sub-region is provided with the detection mark.

Images