Planarization method of composite interface

Abstract

The invention discloses a planarization method of a composite interface. The planarization method of the composite interface comprises the steps that an initial wafer to be ground is provided, the initial wafer comprises a substrate and a composite layer arranged on one side of the substrate, the composite layer comprises a metal part and an organic part which are arranged in a staggered mode, and the initial height of the metal part is larger than that of the organic part; first-stage grinding is conducted on the initial wafer through first grinding liquid to obtain a first-stage wafer, the height of the metal part in the first-stage wafer is larger than that of the organic part, and the height difference between the metal part and the organic part in the first-stage wafer is smaller than that between the metal part and the organic part in the initial wafer; second-stage grinding is conducted on the first-stage wafer through second grinding liquid to obtain a second-stage wafer, and the metal part and the organic part in the second-stage wafer reach the target height; carrying out tempering treatment on the second-stage wafer; and cleaning the second-stage wafer to obtain a target wafer. The method can improve the flatness of the composite interface.

Description

Technical Field

[0001] This application belongs to the field of semiconductor device manufacturing technology, and specifically relates to a method for planarizing composite interfaces. Background Technology

[0002] In semiconductor device manufacturing, chemical mechanical planarization (CMP) is widely used for wafer surface polishing to achieve high-precision, smooth surfaces. With the evolution of 3D integration technology, hybrid bonding methods are increasingly employed in wafer-level packaging, particularly the combination of metallic and organic materials. Metallic materials such as copper or aluminum possess high hardness and low chemical reactivity, while organic materials like polymers exhibit low hardness and high chemical sensitivity. This significant difference in physicochemical properties leads to a slower polishing rate for the metallic portion and a faster polishing rate for the organic portion during traditional planarization, resulting in a noticeable inconsistency on the wafer surface. Current planarization methods struggle to simultaneously regulate the polishing behavior of both materials, causing localized bulges or depressions at the interface and a decrease in surface smoothness. This uneven interface not only interferes with the precise alignment of subsequent bonding processes but also easily leads to defects such as interface delamination and unstable electrical connections, severely impacting the overall performance and reliability of semiconductor devices. Summary of the Invention

[0003] To address the aforementioned technical problems, this application provides a method for planarizing composite interfaces, which can effectively improve the flatness and cleanliness of composite interfaces.

[0004] The technical solution adopted to achieve the purpose of this application is as follows: This application provides a method for planarizing a composite interface, including: An initial wafer to be polished is provided; the initial wafer includes a substrate and a composite layer disposed on one side of the substrate, the composite layer including staggered metal portions and organic portions, the initial height of the metal portions being greater than the initial height of the organic portions; The initial wafer is polished in a first stage using a first polishing slurry to obtain a first-stage wafer; the height of the metal portion in the first-stage wafer is greater than the height of the organic portion, and the height difference between the metal portion and the organic portion in the first-stage wafer is less than the height difference between the metal portion and the organic portion in the initial wafer. The first-stage wafer is polished in a second stage using a second polishing slurry to obtain a second-stage wafer, and the metal and organic portions in the second-stage wafer reach the target height. The second-stage wafer is tempered. The second-stage wafer is cleaned to obtain the target wafer.

[0005] In some embodiments, the ratio of the initial height of the metal portion to the initial height of the organic portion ranges from 1.1 to 1.2.

[0006] In some embodiments, the ratio of the initial height of the metal part to the target height of the metal part ranges from 1.05 to 1.2; and / or, the ratio of the initial height of the organic part to the target height of the organic part ranges from 1.05 to 1.2.

[0007] In some embodiments, prior to performing a second-stage polishing on the first-stage wafer using a second polishing slurry, the method further includes: The first-stage wafer is tempered. The wafer in the first stage is cleaned.

[0008] In some embodiments, when tempering the first-stage wafer, the processing temperature range is 80~300°C, and the processing time ranges from 20~120 min; and / or, When cleaning the wafer in the first stage, the processing gas includes oxygen and argon, the volume ratio of oxygen to argon is in the range of 1 to 3, the processing temperature is in the range of -20℃ to 10℃, and the processing time is in the range of 10 to 20 seconds.

[0009] In some embodiments, when tempering the second-stage wafer, the processing temperature range is 60~100°C, and the processing time ranges from 3~5 hours; and / or, When cleaning the wafer in the second stage, the processing gas includes argon, the processing temperature range is -20℃ to 10℃, and the processing time ranges from 30 to 50 seconds.

[0010] In some embodiments, the second-stage polishing of the first-stage wafer using a second polishing slurry includes: The first stage wafer is polished for the first time using a second polishing slurry, so that the height difference between the metal part and the organic part is less than the height difference between the metal part and the organic part in the first stage wafer. The first-stage wafer is polished a second time using the second polishing slurry, so that the height of the metal part and the organic part reaches the transition height. The first-stage wafer is polished a third time using the second polishing slurry, so that the height of the metal part and the organic part reaches the target height.

[0011] In some implementations, the ratio of the transition height to the target height ranges from 1.05 to 1.2.

[0012] In some embodiments, the second polishing fluid includes the first polishing fluid and an additive, wherein the volume ratio of the first polishing fluid to the additive is in the range of 100:1 to 20:1.

[0013] In some embodiments, the height difference between the metal portion and the organic portion in the first stage wafer is less than or equal to 5 μm; after the first stage wafer is polished for the first time using the second polishing slurry, the height difference between the metal portion and the organic portion ranges from 0.5 to 2 μm.

[0014] As can be seen from the above technical solution, this application overcomes the problem of poor compatibility in handling composite interfaces by setting the height of the metal portion in the initial wafer to be greater than the height of the organic portion and adopting a staged grinding strategy. This allows for flexible adjustment of the grinding slurry formulation and grinding parameters according to the planarization requirements of different stages throughout the planarization process. Furthermore, by adding tempering and cleaning treatments after grinding, the structure and properties of the material can be optimized, providing a more stable surface for subsequent processes, while ensuring the cleanliness of the wafer surface and avoiding the negative impact of grinding residues on subsequent bonding. These post-processing steps, combined with staged grinding, form a complete and efficient planarization technology system, significantly improving the flatness of the composite interface and thus providing a solid foundation for high-reliability wafer-level bonding. Attached Figure Description

[0015] Figure 1 A flowchart illustrating a method for flattening a composite interface as provided in an embodiment of this application; Figure 2 Provided for the embodiments of this application Figure 1 A schematic diagram of the structure corresponding to the completion of step S100; Figure 3 Provided for the embodiments of this application Figure 1 A schematic diagram of the structure corresponding to the completion of step S200; Figure 4 Provided for the embodiments of this application Figure 1 A schematic diagram of the structure corresponding to step S300 in the manufacturing process; Figure 5 Provided for the embodiments of this application Figure 1 A schematic diagram of the structure corresponding to the completion of step S500.

[0016] Explanation of reference numerals in the attached figures: 1-Initial wafer; 11-Substrate; 12-Composite layer; 121-Metal section; 122-Organic section; 2 - First-stage wafer; 3 - Second-stage wafer; 4 - Target wafer; h1 - Transition height; h2 - Target height Detailed Implementation To enable those skilled in the art to better understand this application, the technical solution of this application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] In semiconductor device manufacturing, chemical mechanical polishing (CMP) is used to planarize dielectric materials. However, the differences in physical and chemical properties between metallic and organic materials mean that existing polishing processes cannot simultaneously meet the polishing requirements of both. Metallic materials have higher hardness and lower chemical reactivity, while organic materials have lower hardness and higher chemical reactivity. This mismatch in polishing rates under single polishing conditions results in excessive surface height differences. This issue affects the flatness of the wafer bonding interface, thereby reducing bonding strength and the reliability of electrical connections.

[0018] In response, this application provides a method for planarizing composite interfaces. Please refer to [link to relevant documentation]. Figure 1 The method mainly includes the following steps: S100, Provide an initial wafer 1 to be polished; the initial wafer 1 includes a substrate 11 and a composite layer 12 disposed on one side of the substrate 11, the composite layer 12 includes metal portions 121 and organic portions 122 disposed alternately, the initial height of the metal portions 121 is greater than the initial height of the organic portions 122.

[0019] First, provide an initial wafer 1 to be ground. (See also...) Figure 2 The initial wafer 1 can be fabricated using semiconductor manufacturing processes. It includes a substrate 11 and a composite layer 12 disposed on one side of the substrate 11. The composite layer 12 is composed of staggered metal portions 121 and organic portions 122. In the initial state, due to differences in material deposition or etching processes, the initial height of the metal portions 121 can be designed to be greater than the initial height of the organic portions 122. For example, the initial wafer 1 can be obtained by forming a copper interconnect layer and a polymer dielectric layer on a silicon substrate 11 using a damascus process, wherein the height of the copper layer is higher than that of the polymer layer.

[0020] The initial thickness of the metal part 121 and the organic part 122 can be set in the range of 20~200μm, for example, 20μm, 50μm, 100μm, 150μm or 200μm, etc. The specific thickness value can be selected and adjusted according to the actual design requirements, and no special limitation is made here.

[0021] S200. The initial wafer 1 is polished in the first stage using the first polishing slurry to obtain the first stage wafer 2. The height of the metal part 121 in the first stage wafer 2 is greater than the height of the organic part 122, and the height difference between the metal part 121 and the organic part 122 in the first stage wafer 2 is less than the height difference between the metal part 121 and the organic part 122 in the initial wafer 1.

[0022] Next, please refer to Figure 3 The initial wafer 1 is ground in a first stage using a first polishing slurry to obtain a first-stage wafer 2. This first-stage polishing can employ chemical mechanical polishing (CMP) technology. In this stage, the selection of the first polishing slurry and the control of the polishing parameters aim to effectively remove the metal portion 121, thereby effectively reducing the height difference between the two. For example, a polishing slurry with a high removal rate for metal materials can be selected, while also having some removal capability for organic materials. By controlling the polishing time, polishing pressure, and polishing slurry flow rate, the height of the metal portion 121 in the first-stage wafer 2 can still be greater than the height of the organic portion 122, but the height difference is significantly smaller than the height difference between the metal portion 121 and the organic portion 122 in the initial wafer 1. The purpose of the first-stage polishing is to quickly eliminate most of the initial height unevenness, laying the foundation for subsequent fine planarization.

[0023] S300, The first stage wafer 2 is polished in the second stage using the second polishing slurry to obtain the second stage wafer 3, and the metal part 121 and the organic part 122 in the second stage wafer 3 reach the target height h2.

[0024] Please see Figure 4 Subsequently, the first-stage wafer 2 is polished using a second polishing slurry to obtain the second-stage wafer 3, achieving a target height h2 for the metal portion 121 and the organic portion 122 within the second-stage wafer 3. This second-stage polishing is also achieved using chemical mechanical polishing (CMP) technology. Unlike the first-stage polishing, the second-stage polishing focuses more on achieving precise control over the final surface flatness and the target height h2. The second polishing slurry can be a slurry with a more balanced removal rate for the metal portion 121 and the organic portion 122, or a slurry capable of achieving finer polishing. By precisely adjusting polishing parameters, such as the polishing disc speed, polishing pressure, and polishing slurry formulation, it can be ensured that the height of the metal portion 121 and the organic portion 122 ultimately reaches the preset target height h2, and that the surface has a high degree of flatness.

[0025] S400, Tempering treatment is performed on the second-stage wafer 3.

[0026] After the grinding step is completed, the second-stage wafer 3 undergoes tempering. Tempering is a heat treatment process aimed at improving the physical and chemical properties of the wafer surface material. For example, for metallic materials, tempering can promote grain growth, reduce film stress, and improve the material's density and conductivity; for organic materials, tempering can help improve the material's mechanical strength and dielectric properties, thereby repairing the grinding defects of composite layer 12.

[0027] S500, the second-stage wafer 3 is cleaned to obtain the target wafer 4.

[0028] Finally, please see Figure 5 The second stage involves cleaning wafer 3 to obtain target wafer 4. Cleaning is a critical step in semiconductor manufacturing, designed to remove polishing slurry particles, chemical residues, and other contaminants that may remain on the wafer surface during polishing and tempering. This ensures a clean and flawless surface for target wafer 4, providing a high-quality substrate for subsequent bonding or packaging processes. For example, wet cleaning techniques such as deionized water rinsing, brushing, or ultrasonic cleaning can be used, as well as dry cleaning techniques such as plasma cleaning.

[0029] This embodiment of the application sets the height of the metal portion 121 in the initial wafer 1 to be greater than the height of the organic portion 122, and adopts a staged grinding strategy. This allows for flexible adjustment of the grinding slurry formulation and grinding parameters according to the planarization requirements of different stages throughout the planarization process, thereby overcoming the problem of poor compatibility in handling composite interfaces using traditional methods. Furthermore, by adding tempering and cleaning treatments after grinding, the structure and properties of the material can be optimized, providing a more stable surface for subsequent processes, while ensuring the cleanliness of the wafer surface and avoiding the negative impact of grinding residues on subsequent bonding. These post-processing steps, combined with staged grinding, form a complete and efficient planarization technology system, significantly improving the flatness of the composite interface, thus providing a solid foundation for high-reliability wafer-level bonding.

[0030] In some embodiments, the ratio of the initial height of the metal portion 121 to the initial height of the organic portion 122 ranges from 1.1 to 1.2. This ratio defines a precise range of the initial height difference between the metal portion 121 and the organic portion 122 in the composite layer 12 before polishing begins, ensuring that the metal portion 121 has a moderate and controllable amount of protrusion before polishing. For example, during the preparation of the initial wafer 1, the metal deposition and organic material filling processes can be precisely controlled so that the initial height ratio of the metal portion 121 and the organic portion 122 falls within the range of 1.1 to 1.2 after the composite layer 12 is formed. Furthermore, after the initial wafer 1 is prepared, the initial heights of the metal portion 121 and the organic portion 122 can be detected using high-precision measurement equipment such as non-contact optical measurement or atomic force microscopy, and the preparation process can be adjusted based on the measurement results to ensure that the ratio meets the requirements.

[0031] In the actual design process, the ratio of the initial height of the metal part 121 to the initial height of the organic part 122 can be set to 1.1, 1.15 or 1.2, etc. The specific ratio can be selected and adjusted according to the actual design requirements, and no special limitation is made here.

[0032] This embodiment limits the ratio of the initial height of the metal portion 121 to the initial height of the organic portion 122 to a range of 1.1 to 1.2, ensuring that at the start of the first stage of grinding, the metal portion 121 has a moderate and controllable protrusion relative to the organic portion 122. When the initial wafer 1 is ground using the first polishing slurry, because the height of the metal portion 121 is relatively high and the height difference with the organic portion 122 is within a controlled range, the polishing slurry can preferentially and efficiently act on the metal portion 121, thereby effectively reducing the height of the metal portion 121 and decreasing the height difference between the metal portion 121 and the organic portion 122. Simultaneously, because the initial height of the organic portion 122 is relatively low, unnecessary over-grinding or damage to the organic portion 122 can be avoided during the first stage of grinding. This precise control of the initial height ratio lays a good foundation for the subsequent second stage of grinding, enabling the first stage of grinding to more effectively converge the height difference between the metal portion 121 and the organic portion 122, thereby improving the efficiency and accuracy of the overall planarization process.

[0033] In some embodiments, the ratio of the initial height of the metal portion 121 to its target height h2 ranges from 1.05 to 1.2; and / or, the ratio of the initial height of the organic portion 122 to its target height h2 ranges from 1.05 to 1.2. That is, before grinding begins, the initial thickness of the metal portion 121 and / or the organic portion 122 should be slightly higher than its final required thickness, and this excess should be within a controllable range. By precisely defining the ratio of the initial height of the metal portion 121 and the organic portion 122 in the initial wafer 1 to their respective target height h2, an optimized starting condition is set for the subsequent grinding process. During the planarization of the composite interface, the metal portion 121 and the organic portion 122 have different material properties and grinding rates. If the initial height is too high, it will result in excessively long grinding time, increased consumption of grinding slurry and production costs, and may introduce the risk of over-grinding, causing surface defects such as pitting or corrosion. Conversely, if the initial height is too low, the material may be completely removed before the target flatness is achieved, resulting in the inability to achieve the desired flatness effect and even exposing the underlying structure.

[0034] By controlling these ratios within the range of 1.05 to 1.2, sufficient material allowance is ensured at the start of grinding to remove surface irregularities and achieve global planarization, while avoiding unnecessary material waste and excessively long grinding times. This preset material budget allows for more efficient and precise first-stage and second-stage grinding, making it easier for the metal portion 121 and the organic portion 122 to reach the target height h2 and obtain a high-quality planarized wafer.

[0035] In the actual design process, this ratio can be set to 1.05, 1.1, 1.15 or 1.2, etc. The specific ratio can be selected and adjusted according to the actual design requirements, and no special limitation is made here.

[0036] Since the first-stage grinding may result in stress or residue on the wafer surface, affecting the uniformity of subsequent grinding and the final planarization effect, in some embodiments, before performing the second-stage grinding on the first-stage wafer 2 using the second polishing slurry, the process further includes tempering the first-stage wafer 2 and cleaning the first-stage wafer 2.

[0037] Tempering the first-stage wafer 2 is a heat treatment process designed to eliminate internal stresses generated during processing and improve the material's microstructure and properties. For the first-stage wafer 2, surface stress or microscopic damage may occur due to mechanical action during the first-stage grinding process. Tempering effectively releases these stresses, stabilizing the wafer surface structure and providing a more uniform and stable starting surface for the subsequent second-stage grinding. Tempering can be achieved by heating the wafer in a specific temperature environment, such as in a vacuum furnace or inert gas furnace, or through localized heating methods such as laser annealing.

[0038] Simultaneously, the cleaning process for wafer 2 in the first stage aims to remove any residual polishing slurry, polishing particles, metal debris, or other contaminants that may remain on the wafer surface after the first stage of polishing. If these residues are not removed promptly, they may cause secondary contamination, scratch the wafer surface, or even affect the chemical action of the polishing slurry during the subsequent second stage of polishing, thereby reducing planarization quality. Cleaning can be performed in various ways, such as rinsing with deionized water combined with ultrasonic cleaning to enhance particle removal; or using cleaning solutions containing specific chemical reagents, such as dilute acids, dilute alkalis, or organic solvents, to dissolve or remove specific types of contaminants; or employing dry cleaning techniques such as plasma cleaning.

[0039] In some embodiments, when tempering the first-stage wafer 2, the processing temperature range can be set to 80~300℃, and the processing time can be set to 20~120min; and / or, when cleaning the first-stage wafer 2, the processing gas can be oxygen and argon, the ratio of the volume of oxygen to the volume of argon can be set to 1~3, the processing temperature range can be set to -20℃~10℃, and the processing time range can be set to 10~20s.

[0040] Tempering aims to eliminate internal stresses generated during the first stage of wafer polishing through thermal energy, stabilize the material's microstructure, and improve its surface condition. Controlling the processing temperature within the range of 80–300°C ensures effective stress release and structural rearrangement while avoiding excessive material diffusion or wafer damage that may result from excessively high temperatures. Setting the processing time to 20–120 minutes ensures sufficient stress relief while maintaining process efficiency. In addition to single-temperature tempering, segmented heating or cooling tempering profiles can be used to more precisely control the stress release process.

[0041] The cleaning process removes residual polishing slurry, particulate contaminants, and any oxide layers that may have formed on the wafer surface after the first stage of polishing. The processing gas contains oxygen and argon. Oxygen effectively oxidizes organic residues, making them easier to remove, or forms a thin, uniform oxide layer on the metal surface for subsequent processing. Argon, as an inert gas, provides physical bombardment to aid in particle removal and acts as a dilution gas to adjust the oxygen concentration. By setting the oxygen-to-argon volume ratio to 1–3, a balance between oxidation and physical removal is ensured. The power during the cleaning process can be set to 600–1000 W, the oxygen flow rate to 100–800 Sccm, and the pressure to 50–200 mTorr.

[0042] By setting the processing temperature range to -20℃ to 10℃, low-temperature cleaning can be achieved, effectively reducing the impact of thermal stress on the wafer. This is particularly suitable for temperature-sensitive materials, while avoiding surface chemical reactions or contaminant solidification that may be caused by high temperatures. By setting the processing time range to 10~20s, the thoroughness of contaminant removal is ensured, while avoiding surface erosion that may be caused by prolonged processing.

[0043] In some embodiments, when tempering the second-stage wafer 3, the processing temperature range can be set to 60~100℃ and the processing time range can be set to 3~5h; and / or, when cleaning the second-stage wafer 3, the processing gas may include argon, the processing temperature range can be set to -20℃~10℃ and the processing time range can be set to 30~50s.

[0044] For wafers, tempering effectively releases stress generated during grinding, repairs lattice damage, and promotes homogenization of the internal structure of the composite layer 12. Setting the processing temperature in a relatively low range of 60–100°C aims to gently release stress, avoiding thermal damage or decomposition of the organic portion 122 in the composite layer 12, while ensuring proper grain rearrangement or stress relaxation of the metal portion 121. For example, a resistance furnace or non-contact heating via an infrared lamp array can be used. Setting the processing time in a relatively long range of 3–5 hours helps ensure sufficient heat penetration into the wafer, making the stress release and structural stabilization process more thorough.

[0045] The cleaning process aims to remove particles, organic matter, metal ions, or other contaminants that may remain on the wafer surface after grinding and tempering, ensuring surface cleanliness and guaranteeing the performance of subsequent processes or the final product. Argon can be selected as the processing gas. Argon is an inert gas that serves as a carrier gas or auxiliary medium in the cleaning process. It can physically purge surface particles or act as a plasma source in plasma cleaning, removing contaminants through physical bombardment without chemically reacting with the wafer surface, thus avoiding the introduction of new contamination or damage. The argon flow rate can be set to 100–300 sccm, and the pressure to 50–200 mTorr.

[0046] Setting the processing temperature within a relatively low range of -20°C to 10°C helps avoid thermal damage to the wafer surface during cleaning, especially for the composite layer 12 containing the organic portion 122, where low temperatures effectively inhibit the degradation or deformation of organic matter. Setting the processing time within a relatively short range of 30 to 50 seconds allows for efficient removal of surface contaminants while reducing excessive exposure to the wafer surface and mitigating the risk of potential damage.

[0047] In the second-stage grinding process, directly grinding to the target height h2 in one go may make it difficult to precisely control the grinding amount, leading to over- or under-grinding, which in turn affects the flatness and surface quality of the final wafer, especially in the planarization of composite interfaces requiring extremely high flatness. In some embodiments, please refer to... Figure 4 When performing a second-stage polishing on the first-stage wafer 2 using a second polishing slurry, the following steps can be adopted: The first-stage wafer 2 is polished for the first time using the second polishing slurry, so that the height difference between the metal part 121 and the organic part 122 is less than the height difference between the metal part 121 and the organic part 122 in the first-stage wafer 2; the first-stage wafer 2 is polished for the second time using the second polishing slurry, so that the height of the metal part 121 and the organic part 122 reaches the transition height h1; and the first-stage wafer 2 is polished for the third time using the second polishing slurry, so that the height of the metal part 121 and the organic part 122 reaches the target height h2.

[0048] In this process, the first-stage wafer 2 is polished using a second polishing slurry to reduce the height difference between the metal portion 121 and the organic portion 122 to a smaller value than the height difference between the metal portion 121 and the organic portion 122 in the first-stage wafer 2. This step marks the beginning of the second-stage polishing, and its main purpose is to initially reduce the height difference between the metal portion 121 and the organic portion 122 while ensuring polishing efficiency. Through this first polishing, the wafer is further planarized from its state after the first-stage polishing (the height of the metal portion 121 is still greater than the height of the organic portion 122, but the height difference has been reduced), laying the foundation for subsequent fine polishing. Lower polishing pressure and / or shorter polishing time can be used to gently remove some material and avoid over-polishing. Furthermore, the polishing rate can be controlled by adjusting the flow rate of the polishing slurry or the rotation speed of the polishing disc to ensure effective reduction of the height difference.

[0049] The first-stage wafer 2 is polished a second time using a second polishing slurry, bringing the height of the metal portion 121 and the organic portion 122 to a transition height h1. This step is crucial, aiming to polish the wafer to a preset "transition height h1." This transition height h1 is slightly higher than the final target height h2, its purpose being to allow for a certain margin in the final fine polishing, while ensuring that the overall flatness of the wafer has reached a high level before reaching the target height h2. The polishing time can be precisely calculated based on the material removal rate and the target transition height h1, and the polishing parameters can be adjusted in real time using an online monitoring system. Alternatively, a second polishing slurry with a specific polishing selectivity ratio (the polishing rate ratio of metal to organic material) can be selected to more effectively control the height of the metal portion 121 and the organic portion 122.

[0050] The first-stage wafer 2 is polished a third time using a second polishing slurry to bring the height of the metal portion 121 and the organic portion 122 to the target height h2. This is the final step of the second-stage polishing, and its core objective is to achieve final and precise planarization, ensuring that the height of the metal portion 121 and the organic portion 122 reaches the preset target height h2. Since the first two polishing processes have significantly reduced the height difference and brought it close to the target, the third polishing can be more precisely controlled to obtain a high-quality surface. Ultra-precision polishing can be performed using extremely low polishing pressure, extremely short polishing time, or more diluted polishing slurry to achieve nanometer-level planarity requirements. Furthermore, endpoint detection technologies, such as optical interferometers or capacitive sensors, can be combined to monitor the wafer surface height in real time, stopping polishing once the target height h2 is reached, ensuring precise control.

[0051] By subdividing the second-stage grinding process into three stages, finer control over the planarization process of the composite interface is achieved. First, the first grinding stage aims to quickly and effectively reduce the significant height difference between the metal portion 121 and the organic portion 122, creating conditions for subsequent precision grinding. Then, the second grinding stage grinds the wafer to a preset transition height h1, slightly higher than the final target height h2, thus ensuring overall planarity while providing operational margin for the final precision grinding. Finally, the third grinding stage performs ultra-precision grinding on the basis that the height difference is now very small and close to the target height h2, ensuring that the metal portion 121 and the organic portion 122 accurately reach the target height h2 and achieve extremely high surface flatness. This staged, progressive grinding strategy effectively avoids the problems of over-grinding or under-grinding that may occur with traditional one-stage grinding, significantly improving grinding accuracy and the final wafer quality.

[0052] In some embodiments, the ratio of the transition height h1 to the target height h2 ranges from 1.05 to 1.2. The transition height h1 refers to an intermediate height reached by the metal portion 121 and the organic portion 122 after the second polishing of the first-stage wafer 2 using the second polishing slurry. It sets a preset starting state for the subsequent third polishing, breaking down the complex polishing process into more controllable stages and avoiding the risks of over-polishing or under-polishing that might occur if the target height h2 is reached all at once. The target height h2 refers to the height expected to be reached at the end of the entire composite interface planarization process, i.e., the ideal flatness that the metal portion 121 and the organic portion 122 should ultimately achieve.

[0053] By limiting the ratio of the transition height h1 to the target height h2 within the range of 1.05 to 1.2, the aim is to ensure that there is still sufficient material allowance for the subsequent third grinding when the transition height h1 is reached, while avoiding excessive allowance that would lead to an overly long or inefficient third grinding process. For example, if the ratio is too small, the transition height h1 and the target height h2 may become too close, increasing the difficulty of controlling the third grinding process and making over-grinding more likely; if the ratio is too large, it means that the transition height h1 is still much higher than the target height h2, which would increase the burden and time of the third grinding process.

[0054] In some embodiments, the second polishing slurry comprises a first polishing slurry and an additive. The additive is a substance added to the first polishing slurry to modify its polishing properties, thereby forming the second polishing slurry. These additives can be selected based on the polishing target and material properties to optimize polishing rate, selectivity, surface roughness, or flatness. The additive can be a chemical substance capable of improving the selective polishing of the organic component 122, such as a complexing agent, corrosion inhibitor, or surfactant. For example, when photoresist or BCB (benzocyclobutene) is used as the organic component 122, PGMEA (Propylene Glycol Monomethyl Ether Acetate) can be selected as the additive to achieve polishing of the organic material during the second-stage polishing process. Furthermore, the additive can also be an acid or base used to adjust the pH of the polishing slurry, or a dispersant used to change the dispersion state of the polishing particles.

[0055] The volume ratio of the first polishing slurry to the additive ranges from 100:1 to 20:1. This ratio is crucial for controlling the polishing performance of the second polishing slurry. For example, when the additive ratio is low (close to 100:1), the performance of the second polishing slurry may be closer to that of the first slurry, suitable for stages requiring high polishing rates on metals; while when the additive ratio is high (close to 20:1), the additive's effect is more significant, potentially leading to a decrease in polishing rate or increased selectivity, suitable for stages requiring fine control and high flatness, such as polishing efficiency compatible with both metals and organic materials. Precise control of this ratio helps optimize the polishing process and ensures the quality of the final wafer.

[0056] It should be noted that the second polishing slurry is not entirely independent of the first polishing slurry, but rather formed by adding specific additives to the first polishing slurry. This design allows the second polishing slurry to inherit some of the basic polishing characteristics of the first polishing slurry, while its polishing performance can be finely controlled through the introduction of additives. This method of customizing the performance of the second polishing slurry by adjusting the proportion of additives allows the entire polishing process to better adapt to the needs of different stages, thus effectively solving the technical problem that a single fixed-component polishing slurry cannot simultaneously achieve both efficiency and precision, ensuring efficient and high-precision planarization of the composite interface.

[0057] In some embodiments, the height difference between the metal portion 121 and the organic portion 122 in the first-stage wafer 2 is less than or equal to 5 μm. This limitation aims to ensure that after the first-stage grinding, the height difference between the metal portion 121 and the organic portion 122 on the wafer surface is controlled within a small range. This provides a flatter starting surface for subsequent fine grinding stages, thereby reducing the difficulty of fine grinding and minimizing the risk of grinding defects caused by initial unevenness. This can be achieved by precisely controlling the process parameters of the first-stage grinding, for example, adjusting the formulation of the first grinding slurry to optimize the selective removal rate of the metal portion 121 and the organic portion 122, or by adjusting mechanical parameters such as grinding pressure, grinding disc speed, and grinding time to ensure that most of the initial height difference is removed while avoiding over-grinding or introducing new inhomogeneities. For example, a first grinding slurry with a high metal removal rate and a low organic removal rate can be used, combined with appropriate grinding pressure and time, to achieve the desired flatness at the end of the first stage.

[0058] Correspondingly, after the first polishing of the first-stage wafer 2 using the second polishing slurry, the height difference between the metal portion 121 and the organic portion 122 ranges from 0.5 to 2 μm. This limitation further clarifies the height difference between the metal portion 121 and the organic portion 122 after the completion of the first polishing sub-stage in the second-stage polishing. Controlling this height difference within a narrow range of 0.5 to 2 μm indicates that this sub-stage aims to achieve a finer planarization of the wafer surface, preparing for subsequent polishing to reach the target height h2. This can be achieved by optimizing the composition of the second polishing slurry and the process conditions of the first polishing. For example, the second polishing slurry can be designed to have closer removal rates for the metal portion 121 and the organic portion 122 to achieve gentler and more uniform material removal. At the same time, lower polishing pressure, slower polishing disc speed, and shorter polishing time can be used to precisely control the amount of material removed, ensuring that the height difference is effectively and stably reduced to the target range.

[0059] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0060] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for planarizing a composite interface, characterized in that, The method includes: An initial wafer to be polished is provided; the initial wafer includes a substrate and a composite layer disposed on one side of the substrate, the composite layer including staggered metal portions and organic portions, the initial height of the metal portions being greater than the initial height of the organic portions; The initial wafer is polished in a first stage using a first polishing slurry to obtain a first-stage wafer; the height of the metal portion in the first-stage wafer is greater than the height of the organic portion, and the height difference between the metal portion and the organic portion in the first-stage wafer is less than the height difference between the metal portion and the organic portion in the initial wafer. The first-stage wafer is polished in a second stage using a second polishing slurry to obtain a second-stage wafer, and the metal and organic portions in the second-stage wafer reach the target height. The second-stage wafer is tempered. The second-stage wafer is cleaned to obtain the target wafer.

2. The planarization method for composite interfaces according to claim 1, characterized in that, The ratio of the initial height of the metal part to the initial height of the organic part is in the range of 1.1 to 1.

2.

3. The planarization method for composite interfaces according to claim 1, characterized in that, The ratio of the initial height of the metal part to the target height of the metal part is in the range of 1.05 to 1.2; and / or, the ratio of the initial height of the organic part to the target height of the organic part is in the range of 1.05 to 1.

2.

4. The method for planarizing composite interfaces according to claim 1, characterized in that, Before performing the second-stage polishing on the first-stage wafer using the second polishing slurry, the method further includes: The first-stage wafer is tempered. The wafer in the first stage is cleaned.

5. The planarization method for composite interfaces according to claim 4, characterized in that, When tempering the wafer in the first stage, the processing temperature range is 80~300℃, and the processing time ranges from 20~120min; and / or, When cleaning the wafer in the first stage, the processing gas includes oxygen and argon, the volume ratio of oxygen to argon is in the range of 1 to 3, the processing temperature is in the range of -20℃ to 10℃, and the processing time is in the range of 10 to 20 seconds.

6. The method for planarizing composite interfaces according to claim 1, characterized in that, When tempering the wafer in the second stage, the processing temperature range is 60~100℃, and the processing time ranges from 3~5h; and / or, When cleaning the wafer in the second stage, the processing gas includes argon, the processing temperature range is -20℃ to 10℃, and the processing time ranges from 30 to 50 seconds.

7. The method for planarizing composite interfaces according to claim 1, characterized in that, The second-stage polishing of the first-stage wafer using a second polishing slurry includes: The first stage wafer is polished for the first time using a second polishing slurry, so that the height difference between the metal part and the organic part is less than the height difference between the metal part and the organic part in the first stage wafer. The first-stage wafer is polished a second time using the second polishing slurry, so that the height of the metal part and the organic part reaches the transition height. The first-stage wafer is polished a third time using the second polishing slurry, so that the height of the metal part and the organic part reaches the target height.

8. The method for planarizing composite interfaces according to claim 7, characterized in that, The ratio of the transition height to the target height ranges from 1.05 to 1.

2.

9. The method for planarizing composite interfaces according to claim 7, characterized in that, The second polishing fluid includes the first polishing fluid and an additive, wherein the volume ratio of the first polishing fluid to the additive is in the range of 100:1 to 20:

1.

10. The method for planarizing composite interfaces according to claim 7, characterized in that, The height difference between the metal portion and the organic portion in the first stage wafer is less than or equal to 5 μm; after the first stage wafer is polished for the first time using the second polishing slurry, the height difference between the metal portion and the organic portion ranges from 0.5 to 2 μm.

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