A method for improving line width uniformity and topography of photolithography wafers

Abstract

The application provides a method for improving line width uniformity and topography of a photoetching wafer, which comprises the following steps: obtaining a first distribution relationship between line width of a photoresist pattern and exposure dose, and a second distribution relationship between sidewall angle of the photoresist pattern and focus value; setting a target line width and a target sidewall angle, exposing and developing a first wafer using a mask, and obtaining line width data and sidewall angle data of each grating structure on the first wafer; comparing the obtained line width data with the distribution relationship between line width and exposure dose, and comparing the obtained actual sidewall angle data with the distribution relationship between sidewall angle and focus value, and calculating dose offset and focus offset required by each exposure unit in an edge region of the wafer; adjusting exposure parameters of a photoetching machine according to the dose offset and the focus offset, exposing and developing a second wafer, accurately calculating the offset, and improving line width and topography.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more specifically, to a method for improving the linewidth uniformity and morphology of photolithographic wafers. Background Technology

[0002] In semiconductor lithography, linewidth uniformity (CDU) is one of the core indicators for measuring lithography quality. As technology nodes shrink to 55nm and below, the sensitivity of CDU to the uniformity of the preceding thin film growth increases dramatically. Due to the inherent "edge protrusion" and abrupt thickness changes at the wafer edges in chemical vapor deposition or physical vapor deposition processes, the linewidth (CD) and sidewall angle (SWA) of the wafer edge region differ significantly from those of the center region, leading to severe degradation of the overall wafer CDU.

[0003] Currently, the industry mainly uses in-machine compensation for real-time adjustments. While advanced lithography machines are equipped with Dosage Mapping (DOMA) and In-Meter Mapping (IMO) functions, allowing for real-time adjustment of exposure dose and local height based on previous layer thickness feedback during single-wafer exposure, this compensation mechanism only improves the die size (CD). It cannot intervene in real-time for the sidewall angles that determine the final physical shape of the pattern, leading to distortion in the edge pattern morphology. Furthermore, due to the massive computational demands of real-time processing, this compensation is typically only effective for the central wafer region, lacking sufficient response speed and accuracy for edge regions with drastic thickness variations.

[0004] In summary, there is currently a lack of a systematic method for compensating for edge SWA, making it impossible to simultaneously consider the CD size and SWA uniformity at the wafer edge under the condition that the film uniformity remains unchanged. Summary of the Invention

[0005] In view of the problems with the CD size and SWA uniformity of the wafer edge in the prior art, this application provides a method to improve the linewidth uniformity and morphology of photolithographic wafers, which solves the problems in the prior art that take into account both the wafer edge linewidth size and sidewall morphology compensation, and the lack of quantitative correlation between sidewall angle and focus value, which leads to the inability to accurately compensate for edge SWA.

[0006] To achieve the above and other related objectives, the present invention provides a method for improving the linewidth uniformity and morphology of photolithographic wafers, comprising:

[0007] A photomask is provided, the photomask comprising multiple chip pattern regions and scribe line regions located between adjacent chip pattern regions, and multiple grating structures are disposed in the scribe line regions;

[0008] Provide a test wafer to obtain a first distribution relationship between the linewidth of the photoresist pattern and the exposure dose, and a second distribution relationship between the sidewall angle of the photoresist pattern and the focus value;

[0009] Set the target linewidth CD0 and the target sidewall angle SWA0; determine the initial exposure dose D0 according to the first distribution relationship, determine the initial focus value F0 according to the second distribution relationship, expose and develop the first wafer using the mask, and obtain the measured linewidth data CD1 and the measured sidewall angle data SWA1 of the photoresist pattern on the first wafer;

[0010] The measured linewidth data is compared and analyzed with the first distribution relationship, and the measured sidewall angle data is compared and analyzed with the second distribution relationship to calculate the required dose offset ΔD and focus offset ΔF.

[0011] The lithography machine exposure parameters are adjusted according to the dose offset ΔD and the focus offset ΔF to expose and develop the second wafer.

[0012] Optionally, the grating structure includes multiple periodically arranged gratings, the width of which is equal to the distance between two adjacent gratings.

[0013] Optionally, establishing the first distribution relationship between the linewidth and the exposure dose includes:

[0014] Multiple different exposure doses are set, and the photoresist on the test wafer is exposed and developed using the mask to form a photoresist pattern corresponding to the grating structure on the test wafer.

[0015] Obtain the spectral signal reflected by the photoresist pattern;

[0016] Obtain the linewidth value of the photoresist pattern;

[0017] By performing mathematical analysis on the exposure dose and the linewidth value, the distribution relationship between the linewidth and the exposure dose is obtained.

[0018] Optionally, the first distribution relationship between linewidth and exposure dose is as follows: for positive photoresist, the exposure dose is proportional to the linewidth; for negative photoresist, the exposure dose is inversely proportional to the linewidth.

[0019] Optionally, establishing a second distribution relationship between the sidewall angle and the focal value includes:

[0020] Multiple different focus values ​​are set, and the photoresist on the test wafer is exposed and developed using the mask to form a photoresist pattern corresponding to the grating structure on the test wafer.

[0021] Obtain the spectral signal reflected by the photoresist pattern;

[0022] Obtain the angle values ​​of the sidewalls of the photoresist pattern;

[0023] By performing mathematical analysis on the focus value and the sidewall angle value, the distribution relationship between the sidewall angle and the focus value is obtained.

[0024] Optionally, the second distribution relationship between the sidewall angle and the focus value is: the focus value is inversely proportional to the sidewall angle.

[0025] Optionally, using an exposure unit as the compensation unit, the target linewidth CD0 and the target sidewall angle SWA0 within the exposure unit are set, and the target linewidth CD0 and the target sidewall angle SWA0 are the average values ​​within the entire exposure unit; when exposing the second wafer, the dose offset ΔD and the focus offset ΔF corresponding to the exposure unit are obtained, and the same compensation value is used within the same exposure unit.

[0026] Optionally, an exposure unit is divided into multiple exposure areas, and each exposure area is set with its own target linewidth CD0 and target sidewall angle SWA0. When exposing the second wafer, the dose offset ΔD and the focus offset ΔF corresponding to the multiple exposure areas in an exposure unit are obtained.

[0027] Optionally, the grating structures are uniformly distributed in the horizontal and vertical directions within the scribe line area. In one exposure unit, at least N grating structures are provided in the horizontal direction and at least N grating structures are provided in the vertical direction, and N≥7.

[0028] Optionally, it also includes: S6: After exposing and developing the second wafer, measuring and verifying whether the linewidth uniformity and sidewall angle uniformity of the edge region of the second wafer meet the standards; if they meet the standards, locking the dose offset and the focus offset as the production formula for this batch of products, for use in the formal production of the third and subsequent wafers.

[0029] As described above, the method for improving the linewidth uniformity and morphology of photolithographic wafers provided by the present invention has at least the following beneficial technical effects:

[0030] The method for improving the linewidth uniformity and morphology of photolithographic wafers of this invention establishes a first distribution relationship between the photoresist pattern linewidth and the exposure dose, and a second distribution relationship between the sidewall angle and the focus value, thereby achieving simultaneous compensation for the linewidth size and sidewall morphology of the wafer edge region. For the wafer edge region, the preceding thin film exhibits inherent edge protrusions and abrupt thickness changes. This application measures the first wafer to obtain measured linewidth data and measured sidewall angle data for each exposure unit position, and compares and analyzes these data with the first and second distribution relationships, independently calculating the required dose offset and focus offset for each exposure unit. Attached Figure Description

[0031] Figure 1 The flowchart shown is a method for improving the linewidth uniformity and morphology of photolithographic wafers provided in this embodiment.

[0032] Figure 2 The diagram shown is a structural schematic of the mask provided in this embodiment.

[0033] Figure 3 The diagram shown is a schematic diagram of the grating structure provided in this embodiment.

[0034] Figure 4 The image shown is a cross-sectional view of the wafer provided in this embodiment.

[0035] Figure 5 This embodiment shows a schematic diagram illustrating the relationship between linewidth and exposure dose.

[0036] Figure 6 This embodiment shows a schematic diagram illustrating the relationship between the sidewall angle and the focus value.

[0037] Figure 7 The results shown are the measurement results of the wafer edge region before compensation using existing technology.

[0038] Figure 8 The display shows the measurement results of the wafer edge region after compensation using the method provided in this embodiment to improve the uniformity and morphology of the photolithographic wafer linewidth.

[0039] Figure reference numerals: 10, mask; 11, chip pattern area; 12, dicing area; 13, grating structure; 131, grating; 20, wafer. Detailed Implementation

[0040] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components, the shape, quantity, positional relationship and proportion of each component can be arbitrarily changed under the premise of realizing the technical solution of this invention, and the layout of the components may also be more complex.

[0042] Example 1

[0043] This embodiment provides a method for improving the linewidth uniformity and morphology of photolithographic wafers, such as... Figure 1 The diagram shown is a flowchart of a method for improving the uniformity and morphology of the edge linewidth of a photolithographic wafer according to this embodiment, including the following steps:

[0044] S1: Provide a photomask containing multiple chip pattern areas and scribe lines located between adjacent chip pattern areas, with multiple grating structures set within the scribe lines. S2: Provide a test wafer, and obtain a first distribution relationship between the linewidth of the photoresist pattern and the exposure dose, and a second distribution relationship between the sidewall angle of the photoresist pattern and the focus value. S3: Set a target linewidth and a target sidewall angle, determine the initial exposure dose and initial focus value based on the first and second distribution relationships, expose and develop the first wafer using the photomask, and obtain the linewidth data and sidewall angle data of each grating structure on the first wafer. S4: Compare and analyze the measured linewidth data with the first distribution relationship, and compare and analyze the measured sidewall angle data with the second distribution relationship to calculate the required dose offset and focus offset. S5: Adjust the lithography machine exposure parameters based on the dose offset and focus offset, and expose and develop the second wafer.

[0045] Specifically, S1: A mask is provided, each exposure unit of the mask includes multiple chip pattern areas and a dicing track area located between adjacent chip pattern areas, and multiple grating structures are set in the dicing track area;

[0046] like Figure 2 The diagram shown illustrates the structure of the photomask provided in this embodiment. This embodiment provides a photomask 10, which includes multiple chip pattern regions 11 and scribe lines 12 located between adjacent chip pattern regions 11. Taking the plane of the photomask 10 as the X-direction along a certain scribe line direction, and the direction perpendicular to the X-direction within the plane of the photomask 10 as the Y-direction, in this embodiment, the horizontal direction is defined as the X-direction and the vertical direction as the Y-direction. The chip pattern regions 11 are used to form photolithographic patterns for chip functional circuits, and the scribe lines 12 are located between the chip pattern regions 11, crisscrossing in the horizontal and vertical directions to form a grid-like distribution.

[0047] like Figure 3 The diagram shows a schematic of the grating structure provided in this embodiment; multiple grating structures 13 are arranged within the dicing track region 12. Each grating structure 13 includes multiple periodically arranged gratings 131. Generally, the width d1 of each grating 131 and the spacing d2 between two adjacent gratings 131 can be equal or unequal, depending on the actual measurement requirements and process window. In this embodiment, d1 equals d2, meaning the linewidth and spacing of the gratings are equal to obtain the optimal optical diffraction signal intensity and signal-to-noise ratio. Generally, the width of the grating 131 is determined based on the exposure equipment resolution and process window. In this embodiment, the width d1 of the grating 131 is greater than or equal to 0.3 μm, and optionally, it can be 0.3 μm, 0.5 μm, or other values.

[0048] Generally, the overall width L2 of the grating structure 13 (i.e., the total width of all gratings 131 and their spacing) is determined based on the spot size measured by the scattering instrument. Generally, L2 is 20μm-100μm, and more preferably 40μm-60μm. In this embodiment, the length L1 of any grating 131 is 57.5μm. The overall length L1 of the grating structure 13 (i.e., the extension length of each grating 131) is determined based on the width of the scribe line region 12. Generally, L1 is smaller than the width of the scribe line region 12 to ensure that the grating structure 13 is completely located inside the scribe line region 12. Generally, the width of the scribe line region 12 is 60μm-80μm, therefore L1 is 30μm-70μm, preferably 50μm-60μm. In this embodiment, the overall width L2 of the grating structure 13 is 50μm.

[0049] During photolithography, the pattern on the mask 10, including the chip pattern area 11, the dicing area 12, and the grating structure 103, is projected onto the wafer surface to form the pattern of an exposure unit. An exposure unit is the area covered by the photolithography machine in a single exposure on the wafer surface; its size is determined by the field of view of the photolithography machine. Figure 2 The dashed box shown represents an exposure unit, and each exposure unit contains multiple chip pattern areas 11, dicing areas 12, and grating structures 13.

[0050] Specifically, the grating structure 13 is uniformly distributed along the X and Y directions within the scribe line region 12. Generally, within an exposure unit, the grating structure 13 is arranged in an N*N two-dimensional array, where N≥7, and is located at different positions within the exposure unit to cover the entire exposure unit region, ensuring that complete spatial distribution data can be acquired subsequently.

[0051] Specifically, the grating structure 13 is only located within the dicing area 12 and is completely isolated from the chip pattern area 11 in physical position, thus not occupying the effective area of ​​the chip.

[0052] Optionally, multiple sets of grating structures 13 of different sizes can be provided on the photomask 10, corresponding to the central and edge regions of the wafer, respectively. For example, the first set of grating structures 13 has a first period, used to characterize the edge region of the wafer, where there are abrupt changes or other regions; the second set of grating structures 13 has a second period, used to characterize the central region of the wafer. Grating structures 13 with different periods can be respectively set at different positions of the dicing area 12 within the same exposure unit.

[0053] S2: Provide a test wafer to obtain the first distribution relationship between the linewidth of the photoresist pattern and the exposure dose, and the second distribution relationship between the sidewall angle of the photoresist pattern and the focus value.

[0054] like Figure 4 The diagram shows a cross-sectional view of a wafer provided in this embodiment. A test wafer is provided, and a photoresist layer is coated on the surface of the test wafer. The photoresist layer includes positive photoresist and negative photoresist. This embodiment uses positive photoresist for illustration, meaning that the exposed areas are dissolved and removed during development, while the unexposed areas are retained. The top width of the retained photoresist pattern is the linewidth (CD). For negative photoresist, its development characteristics are the opposite of positive photoresist; that is, the exposed areas are retained during development, while the unexposed areas are dissolved and removed.

[0055] Establishing the first distribution relationship between the linewidth and the exposure dose includes: setting multiple different exposure doses; using the mask to expose and develop the photoresist on the test wafer to form a photoresist pattern corresponding to the grating structure on the test wafer; acquiring the spectral signal reflected by the photoresist pattern; acquiring the linewidth value of the photoresist pattern; and performing mathematical analysis on the exposure dose and the linewidth value to obtain the relationship between the linewidth and the exposure dose.

[0056] Specifically, multiple different exposure doses are set in different exposure unit areas of the test wafer 20, while other process conditions remain unchanged. The exposure dose range is determined according to the photoresist type and process window, including 28mJ, 29mJ, 30mJ, 31mJ, 32mJ, etc. The mask 10 provided in step S1 is used to expose and develop each exposure unit area, forming a photoresist pattern corresponding to the grating structure 13 in each area.

[0057] like Figure 5The diagram illustrates the relationship between linewidth and exposure dose provided in this embodiment. Due to different exposure doses, the linewidth (CD) of the photoresist pattern varies in different regions. For positive photoresist, a higher exposure dose results in more complete photoresist decomposition, more dissolution during development, and a smaller retained linewidth (CD) for the photoresist pattern. In other words, there is a negative correlation between exposure dose and linewidth; a higher exposure dose results in a smaller retained linewidth. Similarly, a higher exposure dose results in more photoresist remaining in the exposed area, leading to a larger retained linewidth (CD) for the photoresist pattern. Therefore, there is a positive correlation between exposure dose and linewidth.

[0058] In this embodiment, taking positive photoresist as an example, the first distribution relationship between linewidth and exposure dose is: CD = k1 × D + b1, where CD is linewidth, D is exposure dose, k1 is slope, and b1 is intercept.

[0059] Establishing a second distribution relationship between the sidewall angle and the focus offset includes: setting multiple different focus values, using a mask to expose and develop the photoresist on the test wafer to form a photoresist pattern corresponding to the grating structure on the test wafer; acquiring the spectral signal reflected by the photoresist pattern; acquiring the sidewall angle value of the photoresist pattern; and performing mathematical analysis on the focus value and the sidewall angle value to obtain the relationship between the sidewall angle and the focus value.

[0060] Specifically, the exposure dose of the lithography machine is fixed at the optimal dose point, and multiple different focus values ​​are set for different exposure unit areas of the test wafer 20, while other process conditions remain unchanged. The mask 10 provided in step S1 is used to expose and develop each exposure unit area, forming a photoresist pattern corresponding to the grating structure 13 in each area.

[0061] Specifically, such as Figure 4 As shown, the sidewall angle (SWA) of a photoresist pattern is the angle between the photoresist sidewall and the wafer surface, i.e., the horizontal plane. Ideally, the SWA is 90°, meaning the sidewall of the photoresist pattern is perpendicular to the wafer surface, resulting in the optimal pattern morphology. When the focus value deviates from the optimal focal point, the sidewall angle changes. The further the focus value deviates from the optimal focal point, the smaller the sidewall angle of the photoresist pattern (the more tilted the sidewall), and the worse the pattern morphology becomes. The physical mechanism is that when the lithography lens deviates from the optimal focal plane, the light intensity distribution along the photoresist thickness direction changes, causing the cross-sectional profile of the photoresist pattern after development to change from rectangular to trapezoidal, resulting in a tilted sidewall.

[0062] like Figure 6The diagram illustrates the relationship between the sidewall angle and the focus value provided in this embodiment. By changing the focus value, the photoresist patterns in different regions exhibit differences in sidewall angle (SWA). By linearly fitting the focus value of each exposure unit with the measured sidewall angle value at the corresponding location, a second distribution relationship between the sidewall angle and the focus value can be obtained. The focus value and the sidewall angle are negatively correlated; that is, the larger the focus value, the smaller the sidewall angle. The formula expresses this as: Second distribution relationship between sidewall angle and focus value: SWA = k2 × F + b2, where SWA is the sidewall angle, F is the focus value, k2 is the slope, and b3 is the intercept.

[0063] Specifically, the slopes and intercepts in the first and second distribution relationships are not fixed constants, but vary depending on factors such as wafer material type, photoresist type, exposure equipment model, and optical parameters. By conducting experiments under specific process conditions using the method provided in this application, specific relationships applicable to the current process conditions can be obtained.

[0064] Optionally, in step S2, a scattering instrument is used to read the spectral signal reflected by the photoresist pattern in each exposure unit area, and the spectral characteristic data corresponding to each exposure unit is recorded. A scanning electron microscope is used to acquire the top of the photoresist pattern to obtain the true linewidth (CD) value of the photoresist pattern in each exposure unit area. A scanning electron microscope or a transmission electron microscope (TEM) is used to acquire the cross-section of the photoresist pattern to obtain the actual sidewall angle (SWA) value of the photoresist pattern in each exposure unit area.

[0065] Optionally, the first distribution relationship between the linewidth of the photoresist pattern and the exposure dose, and the second distribution relationship between the sidewall angle of the photoresist pattern and the focus value, can be obtained by combining them on the same test wafer 20. Specifically, focus values ​​or exposure doses are set in different exposure unit regions of the test wafer 20, and photoresist pattern arrays covering different combinations of focus values ​​and exposure doses can be obtained simultaneously through a single exposure and development. Then, two sets of linear relationships can be fitted separately. This method can reduce the impact of inter-wafer process differences on the calibration results.

[0066] S3: Set CD0 and target sidewall angle SWA0, determine initial exposure dose D0 and initial focus value F0 according to the first distribution relationship and the second distribution relationship, expose and develop the first wafer using a mask, and obtain the measured linewidth data and measured sidewall angle data of the photoresist pattern on the first wafer;

[0067] Specifically, the target linewidth CD0 and target sidewall angle SWA0 are first set according to the product design specifications. Generally, the target sidewall angle is 90°, that is, the sidewall is perpendicular to the wafer surface.

[0068] It should be noted that the exposure dose and focus value can be values ​​for the entire exposure unit, or values ​​for a specific exposure point or local area within an exposure unit. For example, in scenarios where the front-layer film has good uniformity and the wafer surface is relatively flat, the lithography machine can uniformly expose each exposure unit on the wafer surface with the same exposure dose and focus value. Specifically, the target linewidth CD0 and target sidewall angle SWA0 are set using a complete exposure unit as the setting unit, and the target linewidth CD0 and target sidewall angle SWA0 are the average values ​​within the entire exposure unit.

[0069] For the exposure unit in the wafer edge region, due to the inherent non-uniformity of the front thin film at the edge (such as edge protrusion or abrupt change in film thickness), an exposure unit is divided into multiple exposure regions. Each exposure region is set with its own target linewidth CD0 and target sidewall angle SWA0. Different exposure regions can be set with different target values ​​to accurately adapt to the actual deviations at different positions of the wafer, especially the severe fluctuations caused by thin film non-uniformity in the edge region.

[0070] Based on the first distribution relationship between linewidth and exposure dose established in step S2, the target linewidth CD0 is used to obtain the initial exposure dose D0 according to the first distribution relationship. Based on the second distribution relationship between sidewall angle and focus value established in step S2, the target sidewall angle SWA0 is used to obtain the initial focus value F0 according to the second distribution relationship. The initial exposure dose D0 and the initial focus value F0 are used as the starting process parameters for the lithography machine to expose the first wafer.

[0071] Using the mask 10 provided in step S1, the first wafer is exposed and developed with the initial exposure dose D0 and initial focus value F0. After exposure and development, a scatterometer is used to read the spectral signals reflected by the grating structures 13 in each exposure unit on the first wafer. These spectral signals are then substituted into the spectral-physical quantity correspondence calibrated in step S2 to obtain the measured linewidth data CD1 and the measured sidewall angle data SWA1 for each corresponding position of the grating structure 13.

[0072] It should be noted that in this embodiment, the first wafer is any wafer from the official product batch, and its exposure and development conditions are completely consistent with those of subsequent product wafers. After the first wafer completes the measurement, it will not proceed to the subsequent etching process. The decision on whether to continue the wafer fabrication or rework will be made after the compensation value is calculated and verified.

[0073] S4: Compare and analyze the measured linewidth data with the first distribution relationship, and compare and analyze the measured sidewall angle data with the second distribution relationship to calculate the required dose offset ΔD and focus offset ΔF;

[0074] The measured linewidth data CD1 of each exposure unit obtained in step S3 is compared and analyzed with the first distribution relationship. Specifically, for one exposure unit on the wafer surface, the measured linewidth is CD1. The measured value is substituted into the inverse function of the first distribution relationship to calculate the actual exposure dose D1 corresponding to the exposure unit. The actual exposure dose D1 is compared with the initial exposure dose D0 set in step S3 to calculate the dose offset ΔD required for the exposure unit: ΔD = D0 − D1. When ΔD is positive, it indicates that the actual exposure dose of the exposure unit is too small, resulting in a larger linewidth, and the dose ΔD needs to be increased in subsequent wafer exposures. When ΔD is negative, it indicates that the actual exposure dose is too large, resulting in a smaller linewidth, and the dose |ΔD| needs to be reduced in subsequent exposures.

[0075] Optionally, for the wafer edge region, the exposure unit is divided into multiple exposure regions. Each exposure region independently calculates its dose offset ΔD and focus offset ΔF. Each exposure region corresponds to a set of independent compensation values ​​to achieve differentiated compensation within the exposure unit.

[0076] Similarly, the measured sidewall angle data SWA1 of each exposure unit is compared and analyzed with the second distribution relationship. The measured sidewall angle value is substituted into the inverse function of the second distribution relationship to calculate the actual focus value F1 corresponding to the exposure unit. The actual focus value F1 is compared with the initial focus value F0 set in step S3 to calculate the required focus offset ΔF for the exposure unit: ΔF = F0 − F1. When ΔF is positive, it indicates that the actual focus value of the exposure unit is too small, resulting in a small sidewall angle, requiring an increase in the focus value in subsequent wafer exposures, with the increase being ΔF. When ΔF is negative, it indicates that the actual focus value is too large, requiring a decrease in the focus value in subsequent exposures, with the decrease being |ΔF|.

[0077] S5: Adjust the lithography machine exposure parameters according to the dose offset and focus offset to expose and develop the second wafer.

[0078] Specifically, the calculated dose offset ΔD and focus offset ΔF are stored in the lithography machine control system or advanced process control system. When exposing the second wafer, the lithography machine superimposes ΔD and ΔF on the initial exposure dose D0 and initial focus value F0 according to the compensation value corresponding to each exposure unit, thereby achieving precise compensation for each exposure unit.

[0079] Specifically, when exposing the second wafer, the lithography machine superimposes ΔD and ΔF onto the initial exposure dose D0 and initial focus value F0 based on the compensation values ​​corresponding to each exposure unit, i.e.: D2 = D0 + ΔD, F2 = F0 + ΔF; where D2 and F2 are the average exposure dose and focus value actually executed by one exposure unit, respectively. During the scanning exposure process, the lithography machine adjusts the exposure dose and focus value in real time according to the pre-stored compensation values ​​of each exposure unit, achieving precise point-by-point compensation for the linewidth and sidewall angle of the wafer edge region.

[0080] Optionally, the lithography machine superimposes ΔD and ΔF on the initial exposure dose D0 and initial focus value F0 respectively, based on the compensation value corresponding to each exposure area within each exposure unit, to achieve differentiated compensation for each exposure area within the exposure unit.

[0081] Optionally, it also includes: S6: After exposing and developing the second wafer, measuring and verifying whether the linewidth uniformity and sidewall angle uniformity of the edge region of the second wafer meet the standards; if they meet the standards, locking the dose offset and the focus offset as the production formula for this batch of products, for use in the formal production of the third and subsequent wafers.

[0082] According to step S5, the second wafer is exposed and developed using the adjusted exposure parameters based on mask 10. The second wafer is from the same product batch as the first wafer, and its front-layer thin film conditions, photoresist coating conditions, and other process environments are completely consistent with those of the first wafer. After exposure and development, a scatterometer is used to read the spectral signals reflected by each grating structure 13 on the second wafer, and the measured linewidth data and measured sidewall angle data of each exposure unit on the second wafer are obtained. The measured data of the second wafer are compared with the target values ​​to verify the compensation effect.

[0083] If the verification is successful, the dose offset ΔD(i) and focus offset ΔF(i) are locked as the production formula for this batch of products and used for the formal production of the third and subsequent wafers. Subsequent wafers are exposed using the same compensation parameters as the second wafer, eliminating the need to repeat the measurement and calculation process of the first wafer for each wafer.

[0084] If the verification fails, check whether the compensation value calculation is correct, or check the status of the lithography machine and whether there are abnormal fluctuations in the previous layer process. If necessary, repeat steps S3 to S5 to redo the measurement of the first wafer, the compensation value calculation, and the verification exposure of the second wafer until the compensation effect meets the process specifications.

[0085] Figure 7 The results are shown as measurement results of the wafer edge region before compensation using existing technology. Figure 8The display shows the measurement results of the wafer edge region after compensation using the method provided in this embodiment to improve the uniformity and morphology of the photolithographic wafer linewidth.

[0086] Before compensation, the sidewall angle uniformity (SWA 3σ) was 2.9; after compensation, the sidewall angle uniformity was 2.03, an overall improvement of about 30%; before compensation, the overall linewidth uniformity (CDU 3σ) was 1.7; after compensation, the overall linewidth uniformity (CDU 3σ) was 1.2, an overall improvement of about 29.4%.

[0087] This invention establishes a first distribution relationship between linewidth and exposure dose, and a second distribution relationship between sidewall angle and focus value through wafer calibration. Then, it obtains full-image distribution data through measurement of the first wafer, and calculates dose compensation value and focus compensation value in reverse, thereby achieving synchronous compensation for linewidth and morphology in the wafer edge region. This can effectively improve the linewidth uniformity and sidewall angle uniformity in the wafer edge region at the same time, and significantly improve the overall pattern quality and product yield of the wafer.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for improving the linewidth uniformity and morphology of photolithographic wafers, characterized in that, include: A photomask is provided, the photomask comprising multiple chip pattern regions and scribe line regions located between adjacent chip pattern regions, and multiple grating structures are disposed in the scribe line regions; Provide a test wafer to obtain a first distribution relationship between the linewidth of the photoresist pattern and the exposure dose, and a second distribution relationship between the sidewall angle of the photoresist pattern and the focus value; Set the target linewidth CD0 and the target sidewall angle SWA0; determine the initial exposure dose D0 according to the first distribution relationship, determine the initial focus value F0 according to the second distribution relationship, expose and develop the first wafer using the mask, and obtain the measured linewidth data CD1 and the measured sidewall angle data SWA1 of the photoresist pattern on the first wafer; The measured linewidth data is compared and analyzed with the first distribution relationship, and the measured sidewall angle data is compared and analyzed with the second distribution relationship to calculate the required dose offset ΔD and focus offset ΔF. The lithography machine exposure parameters are adjusted according to the dose offset ΔD and the focus offset ΔF to expose and develop the second wafer.

2. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 1, characterized in that, The grating structure includes multiple periodically arranged gratings, the width of which is equal to the distance between two adjacent gratings.

3. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 1, characterized in that, Establishing the first distribution relationship between the linewidth and the exposure dose includes: Multiple different exposure doses are set, and the photoresist on the test wafer is exposed and developed using the mask to form a photoresist pattern corresponding to the grating structure on the test wafer. Obtain the spectral signal reflected by the photoresist pattern; Obtain the linewidth value of the photoresist pattern; By performing mathematical analysis on the exposure dose and the linewidth value, the distribution relationship between the linewidth and the exposure dose is obtained.

4. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 3, characterized in that, The first distribution relationship between linewidth and exposure dose is as follows: for positive photoresist, the exposure dose is directly proportional to the linewidth; for negative photoresist, the exposure dose is inversely proportional to the linewidth.

5. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 1, characterized in that, Establishing the second distribution relationship between the sidewall angle and the focal value includes: Multiple different focus values ​​are set, and the photoresist on the test wafer is exposed and developed using the mask to form a photoresist pattern corresponding to the grating structure on the test wafer. Obtain the spectral signal reflected by the photoresist pattern; Obtain the angle values ​​of the sidewalls of the photoresist pattern; By performing mathematical analysis on the focus value and the sidewall angle value, the distribution relationship between the sidewall angle and the focus value is obtained.

6. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 5, characterized in that, The second distribution relationship between the sidewall angle and the focus value is: the focus value is inversely proportional to the sidewall angle.

7. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 1, characterized in that, Using an exposure unit as the compensation unit, the target linewidth CD0 and the target sidewall angle SWA0 within the exposure unit are set, and the target linewidth CD0 and the target sidewall angle SWA0 are the average values ​​within the entire exposure unit; when exposing the second wafer, the dose offset ΔD and the focus offset ΔF corresponding to the exposure unit are obtained, and the same compensation values ​​are used within the same exposure unit.

8. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 1, characterized in that, An exposure unit is divided into multiple exposure areas. Each exposure area is set with its own target linewidth CD0 and target sidewall angle SWA0. When exposing the second wafer, the dose offset ΔD and focus offset ΔF corresponding to the multiple exposure areas in an exposure unit are obtained.

9. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 1, characterized in that, The grating structures are uniformly distributed in the horizontal and vertical directions within the scribe line area. In one exposure unit, at least N grating structures are set along the horizontal direction and at least N grating structures are set along the vertical direction, and N≥7.

10. The method for improving the linewidth uniformity and morphology of photolithographic wafers according to claim 1, characterized in that, Also includes: After exposing and developing the second wafer, the linewidth uniformity and sidewall angle uniformity of the edge region of the second wafer are measured and verified to see if they meet the standards. If the target is met, the dose offset and the focus offset will be locked as the production formula for this batch of products, and used for the formal production of the third and subsequent wafers.

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