Method for regulating wafer warpage and wafer

Abstract

This application discloses a method and a wafer for controlling wafer warpage, relating to the field of semiconductor technology, which can improve the adaptability of wafer fabrication processes. The method for adjusting wafer warpage includes: obtaining an initial warpage distribution of the wafer; determining, based on the initial warpage distribution, a target area on the wafer requiring warpage adjustment and the type of stress required for warpage adjustment, wherein the stress type includes tensile stress and compressive stress, with tensile stress used to reduce the radius of curvature of the wafer warpage and compressive stress used to increase the radius of curvature of the wafer warpage; determining, based on the target area and the corresponding stress type, the number and size of isolation trenches and at least one type of filler material within the target area; etching isolation trenches on the wafer based on the target area and the number and size of the isolation trenches; placing at least one filler material within the isolation trenches; and annealing the wafer with the isolation trenches and filler material.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a method for controlling wafer warpage and a wafer. Background Technology

[0002] In semiconductor manufacturing, multiple thin film deposition processes and etching of the deposited films are required on the wafer. With the increasing complexity of semiconductor processes and the growth in wafer size, the stress introduced during wafer manufacturing can cause significant wafer warping. Currently, wafer warping control technology mainly involves fabricating another thin film layer on top of the wafer. However, this single-layer film material can only achieve compressive or tensile stress, offering only a one-way adjustment of warping direction and failing to adjust warping in different directions in localized areas. This results in poor adaptability to wafer fabrication processes. Summary of the Invention

[0003] This application provides a method and a wafer for controlling wafer warpage, which can improve the adaptability of wafer fabrication processes.

[0004] A first aspect of this application provides a method for adjusting wafer warpage, comprising: Obtain the initial warpage distribution of the wafer; Based on the initial warpage distribution, the target area on the wafer that needs warpage adjustment and the type of stress required to adjust the warpage are determined. The stress type includes tensile stress and compressive stress. The tensile stress is used to reduce the radius of curvature of the wafer warpage, and the compressive stress is used to increase the radius of curvature of the wafer warpage. Based on the target area and the corresponding stress type, determine the number and size of the isolation grooves within the target area, as well as at least one type of filling material; Based on the target area and the number and size of the isolation trenches, isolation trenches are etched on the wafer; At least one of the filling materials is disposed within the isolation groove; The wafer containing the isolation groove and the filling material is annealed.

[0005] In some embodiments, determining the number and size of isolation grooves and at least one type of filling material within the target area, based on the target area and the corresponding stress type, includes: Based on the target area and the corresponding stress type, at least one type of filling material is determined, wherein, when the stress type is tensile stress, the filling material includes at least a stress material with tensile stress characteristics; and when the stress type is compressive stress, the filling material includes at least a stress material with compressive stress characteristics.

[0006] In some embodiments, at least one type of filling material is determined based on the target region and the corresponding stress type, including: Based on the target area and the corresponding stress type, the type and thickness of the filling material are determined, wherein the type of the filling material includes compressive stress characteristic material and tensile stress characteristic material, the compressive stress characteristic material includes multiple types of materials, and the tensile stress characteristic material includes multiple types of materials; When the required stress type in the target area is tensile stress, the number and size of the isolation grooves in the target area are determined based on the fact that the sum of the stresses of the tensile stress characteristic materials in the isolation groove is greater than the sum of the stresses of the compressive stress characteristic materials. The sum of the stresses of the tensile stress characteristic materials is the sum of the products of the thickness of each tensile stress characteristic material and the stress value per unit thickness of the tensile stress characteristic material. The sum of the stresses of the compressive stress characteristic materials is the sum of the products of the thickness of each compressive stress characteristic material and the stress value per unit thickness of the compressive stress characteristic material. When the required stress type in the target area is compressive stress, the number and size of the isolation grooves in the target area are determined based on the fact that the sum of the stresses of the tensile stress characteristic materials set in the isolation groove is less than the sum of the stresses of the compressive stress characteristic materials.

[0007] In some embodiments, determining the number and size of isolation grooves within the target area based on the type, quantity, and thickness of the filling material includes: If the filling material includes a type of stress material and the required stress type for the target area is tensile stress, then a first type of isolation groove is determined to be provided in the target area. When the filling material includes a type of stress material and the required stress type for the target area is compressive stress, a second type of isolation groove is provided in the target area; The diameter of the first type of isolation groove should be less than half the thickness of the tensile stress filling material, and the diameter of the second type of isolation groove should be less than half the thickness of the compressive stress filling material, so as to ensure that both the first type of isolation groove and the second type of isolation groove are filled with the corresponding stress material.

[0008] In some embodiments, the number and size of the isolation grooves within the target area are determined based on the type, quantity, and thickness of the filling material, including: When the filling material includes multiple types and the required stress type for the target area is tensile stress, the thickness ratio of the multiple types of filling materials in the isolation groove is determined based on the fact that the sum of the stresses of the tensile stress characteristic materials in the first type of isolation groove is greater than the sum of the stresses of the compressive stress characteristic materials. The thickness ratio of the multiple stress characteristic materials filling the isolation groove is used to correspond to the stress type of the target area. When the filling material includes multiple types and the target area requires compressive stress, the thickness ratio of the multiple types of filling materials in the isolation groove is determined based on the fact that the sum of the stresses of the tensile stress characteristic materials in the second type of isolation groove is less than the sum of the stresses of the compressive stress characteristic materials. The diameter of the first type of isolation groove should be less than half of the sum of the thicknesses of all tensile stress filling materials, and the diameter of the second type of isolation groove should be less than half of the sum of the thicknesses of all compressive stress filling materials, so as to ensure that both the first type of isolation groove and the second type of isolation groove are filled with the corresponding stress materials.

[0009] In some embodiments, the target region includes a first target region and a second target region, and the method includes: When the filling material includes multiple types, a first type of isolation trench structure is prepared in the first target region by a first round of photolithography and etching processes; A second type of isolation trench structure is fabricated in the second target region through a second round of photolithography and etching processes.

[0010] In some embodiments, the annealing process is performed at a temperature greater than the maximum stress release temperature among all stressed materials.

[0011] A second aspect of this application provides a wafer, wherein the wafer is subjected to warpage adjustment using the method for adjusting wafer warpage as described in any one of the first aspects, the wafer comprising: The device region and the non-functional region, wherein the non-functional region at least partially surrounds the device region, or the non-functional region and the device region are alternately arranged; An isolation groove is provided in the non-functional area; Filling material is placed inside the isolation groove.

[0012] In some embodiments, the non-functional area includes a first target area requiring compressive stress and a second target area requiring tensile stress, and the isolation groove includes a first type of isolation groove and a second type of isolation groove, wherein the first target area is provided with a first type of isolation groove and the second target area is provided with a second type of isolation groove; Wherein, the type of stress material filling the first type of isolation groove is different from the type of stress material filling the second type of isolation groove; and / or, The number of different types of stress materials filling the first type of isolation groove is different from the number of different types of stress materials filling the second type of isolation groove.

[0013] In some embodiments, the stress material includes silicon dioxide and polycrystalline silicon; and / or, The orthographic projection shape of the isolation trench on the wafer includes curved edges or chamfered edges; and / or, The first type of isolation trenches are discretely distributed; and / or, The second type of isolation trenches are discretely distributed.

[0014] This application provides a method for controlling wafer warpage. By measuring and obtaining the initial warpage distribution of the wafer, the method determines the target area on the wafer where warpage adjustment is needed, as well as the stress type required for warpage adjustment in the target area. Based on the actual stress type required in the target area, the method determines the number and size of isolation trenches within the target area, and the filling material within the isolation trenches. Through the combination of the number and size of the isolation trenches and the filling material, the method allows for precise adjustment of the warpage in different areas, enabling the adjustment of various stress magnitudes and types in different target areas. By utilizing the combination of the number and size of the isolation trenches and the filling material, the method achieves diverse adjustments to the overall wafer warpage in three-dimensional space, effectively overcoming the limitation of the single direction of traditional two-dimensional surface stress control and improving the adaptability of wafer fabrication processes. Finally, an annealing process is used to fully release and stabilize the stress state of the filling material, improving both the adaptability of wafer fabrication processes and the stability of wafer stress types. Attached Figure Description

[0015] Figure 1 A schematic flowchart illustrating a method for adjusting wafer warpage according to an embodiment of this application; Figure 2 A schematic diagram of an initial warpage distribution of a wafer provided in an embodiment of this application; Figure 3 A schematic flowchart illustrating a process for manufacturing an isolation tank, as provided in an embodiment of this application; Figure 4 A schematic flowchart illustrating a process for manufacturing an isolation tank, as provided in an embodiment of this application; Figure 5 This is a schematic partial cross-sectional view of a wafer provided in an embodiment of this application. Detailed Implementation

[0016] To better understand the technical solutions provided in the embodiments of this specification, the technical solutions of the embodiments of this specification will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this specification and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this specification, rather than limitations on the technical solutions of this specification. In the absence of conflict, the embodiments of this specification and the technical features in the embodiments can be combined with each other.

[0017] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The term "two or more" includes two or more cases.

[0018] As semiconductor manufacturing processes become more complex and wafer sizes increase, the stress introduced during wafer fabrication can lead to significant wafer warpage. For photolithography, wafer warpage affects linewidth accuracy, overlay accuracy, and can cause focusing failure. For thin film deposition processes, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), wafer warpage results in poor contact with the stage, creating localized temperature differences. Simultaneously, uneven flow and adsorption of reactive gases on the wafer surface cause film thickness deviations. The stress from wafer warpage can further accumulate on the deposited film surface, potentially causing cracks and peeling. For dry etching processes, high warpage leads to uneven etching rates and poor sidewall perpendicularity. For wafer bonding processes, warpage directly affects the contact of the bonding surfaces, determining the success or failure of the bonding process. From a holistic process perspective, many semiconductor processing equipment have strict requirements regarding wafer warpage. Whether the stage is vacuum adsorption or electrostatic adsorption (ESC, E-chuck), excessive warpage will trigger equipment alarms, hindering the manufacturing process.

[0019] Typically, wafer warpage adjustment is concentrated on a two-dimensional plane. For example, a thin film is prepared on the surface or back of the wafer. The thin film material prepared in the whole layer can only achieve compressive or tensile stress, and the warpage adjustment range is small. Moreover, the warpage adjustment direction is singular, and it is impossible to adjust different warpage directions in local areas, resulting in poor adaptability of wafer fabrication process.

[0020] A first aspect of this application provides a method for adjusting wafer warpage. Figure 1 This is a schematic flowchart illustrating a method for adjusting wafer warpage according to an embodiment of this application. For example, as shown... Figure 1 As shown, the methods for adjusting wafer warpage include: S101: Obtain the initial warpage distribution of the wafer.

[0021] Figure 2 This is a schematic diagram of the initial warpage distribution of a wafer provided in an embodiment of this application. For example, an optical profilometer or laser interferometer is used to perform a non-contact scan of the entire wafer to obtain height information at multiple points, generating a three-dimensional model of the wafer.

[0022] S102: Based on the initial warpage distribution, determine the target area on the wafer that needs warpage adjustment and the type of stress required to adjust the warpage. The stress types include tensile stress and compressive stress. Tensile stress is used to reduce the radius of curvature of the wafer warpage, and compressive stress is used to increase the radius of curvature of the wafer warpage.

[0023] For example, refer to Figure 2 The central red area represents the standard warpage. The target areas requiring warpage adjustment include the blue and yellow areas. Using the central red area as a reference, the yellow area represents the wafer's upward warpage along the Z-axis. Compared to the red area, the radius of curvature of the yellow area is smaller. Therefore, the radius of curvature of the yellow area needs to be increased; that is, the stress type required for warpage adjustment in the yellow area is compressive stress. The blue area represents the wafer's downward warpage along the Z-axis. Compared to the red area, the radius of curvature of the blue area is larger. Therefore, the radius of curvature of the blue area needs to be decreased; that is, the stress type required for warpage adjustment in the blue area is tensile stress.

[0024] S103: Determine the number and size of isolation grooves to be set in the target area and at least one type of filling material, based on the target area and the corresponding stress type.

[0025] For example, a simulation software can be used to build a similar... Figure 2The same 3D model of the wafer is used, with the wafer's material properties, geometric dimensions, and the measured target area for warpage adjustment serving as initial boundary conditions. The simulation software can simulate the effect of filling the isolation trenches with at least one type of filler material on the stress type in the yellow and blue regions, using different numbers and sizes of isolation trenches. The software can also systematically adjust key parameters such as the layout, planar shape, depth, density of the isolation trenches in the yellow and blue regions, as well as the stress type and combination ratio of the filler material, to ensure that the radii of curvature of the yellow and blue regions are consistent with those of the red region.

[0026] For example, refer to Figure 2 Using the central red area as a baseline, representing the standard radius of curvature region without warping, the yellow area shows upward warping along the Z-axis, while the blue area shows downward warping. The number and size of isolation trenches were determined using simulation software. Two circular isolation trenches with a diameter of 12μm and a depth of 200μm were selected in the non-functional area of ​​the yellow region. A 2μm thick layer of silicon dioxide and a 6μm thick layer of polysilicon were sequentially grown inside the isolation trenches to ensure complete filling. Similarly, two circular isolation trenches with a diameter of 8μm and a depth of 200μm were selected in the non-functional area of ​​the blue region. A 3μm thick layer of silicon dioxide and a 4μm thick layer of polysilicon were grown inside these isolation trenches to ensure complete filling. The determination of the isolation trenches and filling materials in the yellow and blue regions reduces the warping difference between them, improves wafer surface flatness, and ensures the smooth operation of subsequent processes such as photolithography, thin film deposition, dry etching, and wafer bonding, thereby improving the adaptability of wafer fabrication processes.

[0027] It should be noted that the number of isolation grooves, the depth of the isolation grooves, and the type of filling material in the isolation grooves can all be adjusted according to the actual stress type required by the warpage of the target area, so as to meet the adjustment of different stress types.

[0028] S104: Etch isolation trenches on the wafer according to the target area and the number and size of the isolation trenches.

[0029] Figure 3 This is a schematic flowchart illustrating a process for fabricating an isolation tank, as provided in an embodiment of this application. For example, refer to... Figure 3 Steps S111-S112: Two compressive stress circular isolation trenches with a diameter of 8 μm and a depth of 200 μm are prepared on one side of the wafer using deep reactive ion (DRIE) etching process.

[0030] S105: At least one filling material is provided in the isolation groove.

[0031] For example, refer to Figure 3 Step S103 includes steps S111, S112, S113 and S114, where steps S111 to S114 are the first round of photolithography and etching processes.

[0032] Step S113: First, a silicon dioxide 121 with a thickness of 2 μm is grown on the side of the isolation tank 120 away from the wafer 100 using a furnace tube process. The silicon dioxide 121 is a compressive stress material. Then, a polycrystalline silicon 122 with a thickness of 6 μm is grown using a thin film deposition (LPCVD) process. The polycrystalline silicon 122 is a tensile stress material.

[0033] Step S114: The wafer is polished alternately on the front and back sides using a chemical mechanical polishing (CMP) process, with each side thinned by 2μm each time, for a total of 8 times, to completely remove the two materials outside the isolation trench. The front side of the wafer is the surface with the isolation trench 120, and the back side of the wafer is the side without the isolation trench.

[0034] S106: Annealing the wafer with isolation trenches and filling material.

[0035] For example, a wafer with isolation grooves and filling material can be annealed at a temperature of 1050°C to fully release the stress of the filling material, solidify the stress type of the wafer, prevent changes in subsequent processes, and improve the stability of the wafer stress distribution.

[0036] This application provides a method for controlling wafer warpage. By measuring and obtaining the initial warpage distribution of the wafer, the method determines the target area on the wafer where warpage adjustment is needed, as well as the stress type required for warpage adjustment in the target area. Based on the actual stress type required in the target area, the method determines the number and size of isolation trenches within the target area, and the filling material within the isolation trenches. Through the combination of the number and size of the isolation trenches and the filling material, the method allows for precise adjustment of the warpage in different areas, enabling the adjustment of various stress magnitudes and types in different target areas. By utilizing the combination of the number and size of the isolation trenches and the filling material, the method achieves diverse adjustments to the overall wafer warpage in three-dimensional space, effectively overcoming the limitation of the single direction of traditional two-dimensional surface stress control and improving the adaptability of wafer fabrication processes. Finally, an annealing process is used to fully release and stabilize the stress state of the filling material, improving both the adaptability of wafer fabrication processes and the stability of wafer stress types.

[0037] In some examples, the multiple isolation trenches within the target area are not arranged continuously or connected, but rather distributed independently and separately within the target area, with gaps between each isolation trench. These gaps are non-isolation trench structural areas. By setting the isolation trenches as a discrete distribution rather than a continuous structure, each isolation trench independently undertakes the function of local stress regulation. This allows for precise control of the overall stress magnitude and distribution pattern in the target area by adjusting the number, density, and spatial arrangement of the isolation trenches. On the other hand, the discrete distribution combined with a somewhat chaotic arrangement design effectively avoids the directional accumulation of stress in a specific direction, significantly reducing the risk of wafer mechanical damage caused by stress concentration and improving process safety.

[0038] In some embodiments, step S103 includes: determining at least one type of filling material based on the target area and the corresponding stress type, wherein, when the stress type is tensile stress, the filling material includes at least a stress material having tensile stress characteristics; and when the stress type is compressive stress, the filling material includes at least a stress material having compressive stress characteristics.

[0039] For example, when the stress type required for warpage adjustment in the target area is tensile stress, the isolation groove can be filled with only one type of stress material with tensile stress characteristics, or multiple types of stress materials with tensile stress characteristics, or a combination of stress materials with tensile stress characteristics. Similarly, when the stress type required for warpage adjustment in the target area is compressive stress, the isolation groove can be filled with only one type of stress material with compressive stress characteristics, or multiple types of stress materials with compressive stress characteristics, or a combination of stress materials with tensile stress characteristics. The stress characteristics of the filling materials in the isolation groove and the types of stress materials can be set according to the actual stress requirements to achieve flexibility and diversity in wafer warpage adjustment, thereby improving the adaptability of the wafer fabrication process.

[0040] In some embodiments, step S103 includes: determining the type, quantity, and thickness of the filling material based on the target area and the corresponding stress type, wherein the type of filling material includes compressive stress characteristic material and tensile stress characteristic material, the compressive stress characteristic material includes multiple types of materials, and the tensile stress characteristic material includes multiple types of materials; when the required stress type in the target area is tensile stress, determining the number and size of the isolation grooves in the target area based on the fact that the sum of the stresses of the tensile stress characteristic materials set in the isolation groove is greater than the sum of the stresses of the compressive stress characteristic materials; when the required stress type in the target area is compressive stress, determining the number and size of the isolation grooves in the target area based on the fact that the sum of the stresses of the tensile stress characteristic materials set in the isolation groove is less than the sum of the stresses of the compressive stress characteristic materials.

[0041] For example, the initial warpage value and positional distribution of the wafer can be measured using characterization instruments, and the target area to be adjusted and the direction of the applied stress can be determined in conjunction with specific process requirements. Then, based on the results of physical simulation or engineering experiments, the number and size of the isolation trenches are determined to avoid functional areas of the product and prevent stress concentration. On this basis, according to the type of stress required in the target area, one or more compressive stress characteristic materials and tensile stress characteristic materials are selected for filling, and the magnitude and direction of the stress applied outward by the final isolation trench structure are precisely controlled by adjusting the thickness ratio of the two materials in the isolation trench. For example, in areas requiring tensile stress, the thickness of the filling tensile stress characteristic material is greater than the thickness of the compressive stress material, ensuring that the sum of the tensile stresses generated is greater than the sum of the compressive stresses generated by the compressive stress characteristic materials. Conversely, in areas requiring compressive stress, the thickness of the filling tensile stress characteristic material is less than the thickness of the compressive stress material, ensuring that the sum of the tensile stresses generated is less than the sum of the compressive stresses generated by the compressive stress characteristic materials, thereby achieving precise control of the overall tensile stress output of the target area.

[0042] In some examples, determining the number and size of the isolation grooves requires a comprehensive approach, considering the type and thickness of the filling material and the magnitude of the stress it generates, along with the stress type required by the target area. The net stress value provided by a single isolation groove is determined by the stress characteristics and thickness ratio of the various materials filling it, as well as the groove's geometry, such as depth and diameter. Once the stress contribution of a single isolation groove is determined, the required number of isolation grooves can be calculated based on the total stress adjustment needed for the target area. By combining multiple filling materials with different stress directions within the same isolation groove and precisely controlling their thickness ratios, the limitations of traditional single-material filling in stress control range are overcome. This achieves a high degree of control over the magnitude and direction of stress in a single isolation groove structure, significantly improving the flexibility and accuracy of warpage adjustment.

[0043] In some examples, when there are multiple isolation trenches, each trench can be filled with a different type of material. After determining the stress contribution of a single isolation trench, the total stress can be adjusted according to the required stress in the target area, and the required number and depth of isolation trenches can be calculated. If multiple isolation trenches have the same depth, in a target area where the required stress type is tensile stress, the number of isolation trenches filled with tensile stress material is greater than the number filled with compressive stress material; conversely, in a target area where the required stress type is compressive stress, the number of isolation trenches filled with tensile stress material is less than the number filled with compressive stress material. Furthermore, the multiple isolation trenches are arranged discretely within the target area to avoid overly regular distributions that could lead to stress accumulation in a specific direction, thereby inducing structural damage to the wafer in that direction. By constructing isolation trench structures with specific stress magnitudes and directions in different regions of the wafer, flexible and precise control of the local and overall wafer warpage can be achieved.

[0044] For example, in the yellow area requiring tensile stress, the isolation groove can contain two types of tensile stress characteristic materials and one type of compressive stress characteristic material. In the blue area requiring compressive stress, the isolation groove can contain one type of tensile stress characteristic material and two types of compressive stress characteristic materials. The stress characteristics of the filling material and the types of stress characteristic materials in the isolation groove can be set according to the actual stress requirements to achieve flexibility and diversity in wafer warpage adjustment, thereby improving the adaptability of the wafer fabrication process.

[0045] In some implementations, step S103 includes: when the filling material includes a type of stress material and the required stress type for the target area is tensile stress, determining to set a first type of isolation groove in the target area; when the filling material includes a type of stress material and the required stress type for the target area is compressive stress, setting a second type of isolation groove in the target area; the diameter of the first type of isolation groove should be less than half the thickness of the tensile stress filling material, and the diameter of the second type of isolation groove should be less than half the thickness of the compressive stress filling material, to ensure that both the first type of isolation groove and the second type of isolation groove are filled with the corresponding stress material.

[0046] For example, a first type of isolation trench can be used to achieve tensile stress control, and the first type of isolation trench is filled only with a material having tensile stress characteristics, such as polycrystalline silicon grown by low-pressure chemical vapor deposition. A second type of isolation trench can be used to achieve compressive stress control, and the second type of isolation trench is filled only with a material having compressive stress characteristics, such as silicon dioxide grown by furnace tube thermal oxidation. In this single-material filling scheme, the diameter of the isolation trench must match the thickness of the filling material to ensure that the isolation trench can be completely and defect-free filled.

[0047] In some examples, since there are usually process limits on the deposition or growth thickness of a single material, to ensure that both the first and second type of isolation trenches are completely filled with the corresponding stress-filling material, the diameter of the first type of isolation trench should be smaller than the thickness of the tensile stress-filling material, and the diameter of the second type of isolation trench should be smaller than the thickness of the compressive stress-filling material. In specific process designs, the diameter of the isolation trench is set to be less than half the thickness of the filling material, serving as a safety boundary for process tolerance. This addresses factors such as deposition rate fluctuations, substrate morphology influences, and etching morphology deviations that may occur in actual processes, thereby ensuring that the isolation trench is completely filled with the filling material after thin film deposition or growth, with no depressions or gaps on the surface. For example, when using furnace tube thermal oxidation to grow silicon dioxide as the compressive stress filler material, if the achievable growth thickness is 2 μm, the diameter of the second type of isolation trench is designed to be less than 2 μm, preferably less than 1 μm, to ensure that the silicon dioxide can achieve complete closure and filling of the trench after continuous growth on the sidewalls and bottom. When using low-pressure chemical vapor deposition to grow polycrystalline silicon as the tensile stress filler material, if the deposition thickness is 6 μm, the diameter of the first type of isolation trench is designed to be less than 6 μm, preferably less than 3 μm, to ensure that the polycrystalline silicon can fully fill the trench without creating voids during deposition. Through these dimensional constraints, reliable fabrication of the isolation trench structure under a single material filling scheme is achieved, providing a structural basis for subsequent stress control.

[0048] In some embodiments, step S103 includes: determining to set a first type of isolation groove in the target area when the filling material includes a type of stress material and the required stress type for the target area is tensile stress; and setting a second type of isolation groove in the target area when the filling material includes a type of stress material and the required stress type for the target area is compressive stress, wherein the depth of the first type of isolation groove is the same as the depth of the second type of isolation groove, and the type of filling material set in the first type of isolation groove and the second type of isolation groove is different.

[0049] For example, when the filler material includes a type of stress material, a first type of isolation trench is set in the yellow area, and a second type of isolation trench is set in the blue area. The first and second type of isolation trenches have the same depth, but the types of filler materials used in the first and second type of isolation trenches are different. Specifically, the filler material in the first type of isolation trench includes a stress material with tensile stress characteristics, and the filler material in the second type of isolation trench also includes a stress material with tensile stress characteristics. By setting the same depth in different areas of the wafer, the consistency of the processing can be improved, and the processing difficulty can be reduced. Simultaneously, by using filler materials with different stress characteristics in isolation trenches of the same depth in different areas, the warpage of different areas of the wafer can be adjusted, further reducing the difficulty of wafer processing and improving the efficiency of the wafer processing technology.

[0050] It should be noted that the depths of the first type of isolation groove and the second type of isolation groove can be different, as long as the sum of the stresses of the filling materials inside the isolation groove in the target area meets the corresponding stress requirements. This application does not specifically limit this.

[0051] In some embodiments, step S103 includes: when the filling material includes multiple types of stress materials and the required stress type for the target area is tensile stress, determining that the sum of the filling stresses of the tensile stress characteristic materials among the multiple materials disposed in the first type of isolation groove is greater than the sum of the stresses of the compressive stress characteristic materials, wherein the thickness ratio of the multiple stress characteristic materials filling the isolation groove is used to correspond to the stress type of the target area; when the filling material includes multiple types and the required stress type for the target area is compressive stress, determining that the sum of the stresses of the tensile stress characteristic materials among the multiple materials disposed in the second type of isolation groove is less than the sum of the stresses of the compressive stress characteristic materials.

[0052] For example, when the filling material includes multiple types of stress-prone materials, in the yellow area, the sum of the stresses of the tensile stress-prone materials in the first type of isolation groove is greater than the sum of the stresses of the compressive stress-prone materials, and the diameter of the first type of isolation groove should be less than or equal to the total thickness of the multiple stress-prone materials, meaning that the multiple stress-prone materials fill the first type of isolation groove. In the blue area, the sum of the stresses of the tensile stress-prone materials in the second type of isolation groove is less than the sum of the stresses of the compressive stress-prone materials, and the diameter of the second type of isolation groove should be less than or equal to the total thickness of the multiple stress-prone materials, meaning that the multiple stress-prone materials fill the second type of isolation groove. By setting the filling thickness of different stress-prone materials in the isolation groove, the warpage in the target area can be adjusted more precisely. At the same time, setting the stress-prone materials to fill the isolation groove improves the accuracy of warpage zoning adjustment and improves the flatness of the wafer surface, providing a good process foundation for subsequent wafer fabrication.

[0053] In some examples, where the filling material includes multiple types of stress materials, the diameter of the first type of isolation groove should be less than half the sum of the thicknesses of all tensile stress filling materials, and the diameter of the second type of isolation groove should be less than half the sum of the thicknesses of all compressive stress filling materials, to ensure that both the first and second types of isolation grooves are filled with the corresponding stress materials.

[0054] Figure 4 This is a schematic flowchart illustrating a process for fabricating an isolation tank, as provided in an embodiment of this application. For example, refer to... Figures 3 to 4 In some examples, the target region includes a first target region A and a second target region B. The first target region A includes a yellow area, and the second target region B includes a blue area. A first round of photolithography and etching processes is performed through steps S111 to S114 to form a first type of isolation trench 129 in the first target region A. Step S103 further includes steps S115, S116, S117, and S118, where steps S115 to S118 constitute a second round of photolithography and etching processes to fabricate a second type of isolation trench 139 in the second target region B.

[0055] Steps S111-S112: Two compressive stress circular first-type isolation trenches 129 with a diameter of 8 μm and a depth of 200 μm are prepared on one side of the wafer using deep reactive ion (DRIE) etching process.

[0056] Step S113: First, a silicon dioxide 121 with a thickness of 2 μm is grown on the side of the first type of isolation tank 129 away from the wafer 100 using a furnace tube process. The silicon dioxide 121 is a compressive stress material. Then, a polycrystalline silicon 122 with a thickness of 6 μm is grown using a thin film deposition (LPCVD) process. The polycrystalline silicon 122 is a tensile stress material.

[0057] Step S114: The wafer is polished alternately on the front and back sides using a chemical mechanical polishing (CMP) process, with each side thinned by 2μm each time, for a total of 8 times, to completely remove the two materials outside the isolation trench. The front side of the wafer is the surface with the isolation trench 120, and the back side of the wafer is the side without the isolation trench.

[0058] Step S115: Deposit an optical adhesive layer 200 on the surface of polysilicon 122 away from wafer 100.

[0059] Step S116: Two second-type isolation trenches 139 with a diameter of 12 μm and a depth of 120 μm are formed on one side of polysilicon 122 using a deep reactive ion (DRIE) etching process.

[0060] Step S117: A silicon dioxide material 131 with a thickness of 6 μm is grown in the second type of isolation tank 139 using furnace tube technology. The silicon dioxide material 131 is a compressive stress characteristic material. Then, a polycrystalline silicon material 132 with a thickness of 3 μm is grown using furnace tube technology. The polycrystalline silicon material 132 is a tensile stress characteristic material.

[0061] Step S118: Using a chemical mechanical polishing (CMP) process, alternate grinding is performed on the front and back sides, thinning each side by 2 μm each time, for a total of 6 times, to completely remove the two materials on the surface. The front side of the wafer is the surface with the isolation trench 120, and the back side of the wafer is the side without the isolation trench.

[0062] It should be noted that the etching of the isolation groove can be done in multiple rounds, achieving the ability to control the position, stress magnitude, and direction in multiple dimensions.

[0063] This application's embodiments, through the setting of isolation trenches, ensure that stress-inducing materials are no longer confined to the front or back of the wafer, thus avoiding restrictions or removal from subsequent processes and allowing stress adjustment to be implemented throughout the entire wafer manufacturing lifecycle. Furthermore, by employing two or more rounds of isolation trench fabrication steps, multi-dimensional control over different locations, stress magnitudes, and directions is achieved. Simultaneously, wafer stress can be adjusted through a mixed-material filling scheme to achieve warpage adjustment. This increases the flexibility of material thickness and type combinations, making stress control and filling processes more flexible while reducing process complexity. The stress influence of the material within the isolation trenches is fixed through annealing at a specific temperature, maintaining the stability of warpage adjustment throughout the entire wafer manufacturing lifecycle.

[0064] In some examples, referring to steps S111 to S118, the depth of the first type of isolation trench 129 is the same as the depth of the second type of isolation trench 139, and the type of stress material filled in the first type of isolation trench 129 is different from the type of stress material filled in the second type of isolation trench 139. Specifically, the first type of isolation trench 129 in the first target region A is filled with a filling material with tensile stress characteristics and a filling material with compressive stress characteristics, such as silicon dioxide 121 and polysilicon 122, wherein the sum of the stresses of the silicon dioxide 121 in the first type of isolation trench 129 is greater than the thickness of the polysilicon 122; the second type of isolation trench 139 in the second target region B is filled with a filling material with compressive stress characteristics and a filling material with tensile stress characteristics, such as silicon dioxide material 131 and polysilicon material 132, wherein the sum of the stresses of the silicon dioxide material 131 in the second type of isolation trench 139 is less than the thickness of the polysilicon material 132. By setting the same depth in different regions of the wafer, the consistency of the processing can be improved and the difficulty of the processing can be reduced. At the same time, by setting filling materials with different stress characteristics in the isolation trenches of the same depth in different regions, the warpage of different regions of the wafer can be adjusted.

[0065] In some implementations, the target region includes a first target region and a second target region, and step S103 includes: When the filling material includes multiple types and the stress type required to be provided in the target area is tensile stress, it is determined that the multiple isolation grooves in the first target area have a first arrangement density, and it is determined that the multiple isolation grooves in the second target area have a second arrangement density, wherein the first arrangement density is greater than the second arrangement density. When the filling material includes multiple types and the stress type required to be provided in the target area is compressive stress, it is determined that the multiple isolation grooves in the first target area have a first arrangement density, and it is determined that the multiple isolation grooves in the second target area have a second arrangement density, wherein the first arrangement density is less than the second arrangement density.

[0066] For example, a wafer may include device regions and non-functional regions. The non-functional regions may partially surround the device regions, and the non-functional regions and device regions may be alternately arranged. The target region is located within the non-functional region and may be a scribe line or a reserved dummy region. Setting isolation trenches within the non-functional region to adjust warpage can avoid the functional regions of the product, reducing interference with integrated circuits or microelectromechanical systems (MEMS) devices. When the filler material includes multiple types, multiple isolation trenches are respectively set in a first target region and a second target region, wherein the second target region is located between the device region and the first target region. The multiple isolation trenches in the first target region have a first arrangement density, and the multiple isolation trenches in the second target region have a second arrangement density, with the first arrangement density being greater than the second arrangement density. Alternatively, when the filler material includes multiple types, multiple isolation trenches are respectively set in the first target region and the second target region, wherein the first target region is located between the device region and the second target region, the multiple isolation trenches in the first target region have a first arrangement density, and the multiple isolation trenches in the second target region have a second arrangement density, with the first arrangement density being less than the second arrangement density. By setting isolation trenches with a lower density in a sub-region closer to the device area, the impact of isolation trench fabrication and filling material filling processes on the device area can be reduced. At the same time, setting isolation trenches with a higher density in a sub-region farther from the device area ensures the adjustment of the stress type required for the target area, avoids affecting subsequent processes, and avoids damage to the device, thereby improving the reliability and process adaptability of the wafer.

[0067] It should be noted that regardless of whether the isolation trenches are arranged in the first or second row, the arrangement of the isolation trenches is non-matrix. The isolation trenches have a certain degree of disorder, which can prevent stress concentration in a specific direction due to the overly regular distribution of the isolation trenches, which could cause cracks to appear on the wafer in that direction.

[0068] In some implementations, the annealing process temperature is higher than the maximum value of subsequent process temperatures or the maximum stress release temperature among all stress-relieving materials filling the isolation trenches in different target areas of the wafer. This ensures sufficient stress release of the filling material, solidifies the stress adjustment results, prevents changes in subsequent processes, and improves the stability of the wafer stress distribution.

[0069] For example, the stress-relieving material may include silicon dioxide grown by thermal oxidation and polycrystalline silicon grown by chemical vapor deposition. Silicon dioxide grown by thermal oxidation has a higher growth temperature, generally exceeding 1000℃, and rarely requires annealing to release stress. Polycrystalline silicon grown by chemical vapor deposition typically has a growth temperature between 400 and 600℃, and its stress changes more significantly with temperature. Therefore, the maximum value of the subsequent process temperature or a temperature above 900℃ can be selected for annealing to release stress changes in advance.

[0070] A second aspect of the embodiments of this application provides a wafer whose warpage can be adjusted using the method for adjusting wafer warpage as described in the first aspect. Figure 5 This is a schematic partial cross-sectional view of a wafer provided for an embodiment of this application. For example, as shown... Figure 5 As shown, the wafer includes a device region C and a non-functional region. The non-functional region may partially surround the device region C, and the non-functional region and the device region can be alternately arranged. Isolation trenches are set in the non-functional region, and filling material is placed within the isolation trenches. By setting isolation trenches in the non-functional region of the wafer and filling the isolation trenches with a stress-sensitive material, diverse adjustments to the overall warpage of the wafer are achieved in three-dimensional space. This effectively overcomes the limitation of the single direction of traditional two-dimensional surface stress control, improving the adaptability of wafer fabrication processes. Finally, an annealing process is used to fully release and stabilize the stress state of the filling material, improving both the adaptability of wafer fabrication processes and the stability of wafer stress types.

[0071] In some embodiments, the non-functional region includes a first target region requiring compressive stress and a second target region requiring tensile stress. The first target region is provided with a first type of isolation groove, and the second target region is provided with a second type of isolation groove. The depth of the first type of isolation groove is the same as the depth of the second type of isolation groove, but the type of stress material filling the first type of isolation groove is different from the type of stress material filling the second type of isolation groove; the number of different types of stress material filling the first type of isolation groove is also different from the number of different types of stress material filling the second type of isolation groove.

[0072] For example, refer to Figure 5The non-functional regions include a first target region A requiring compressive stress and a second target region B requiring tensile stress. The first target region A includes a yellow area, and the second target region B includes a blue area. The first target region A is provided with a first type of isolation groove 129, and the second target region B is provided with a second type of isolation groove 139. The depth of the first type of isolation groove 129 is the same as the depth of the second type of isolation groove 139, but the type of stress material filling the first type of isolation groove 129 is different from the type of stress material filling the second type of isolation groove 139. Specifically, the first type of isolation groove 129 in the first target region A is filled with one or more filling materials with tensile stress characteristics, such as silicon dioxide, and the second type of isolation groove 139 in the second target region B is filled with one or more filling materials with compressive stress characteristics, such as polycrystalline silicon. By setting the same depth in different regions of the wafer, the consistency of the processing can be improved and the difficulty of the processing can be reduced. At the same time, by setting filling materials with different stress characteristics in the isolation trenches of the same depth in different regions, the warpage of different regions of the wafer can be adjusted, while reducing the difficulty of wafer processing and improving the efficiency of wafer processing technology.

[0073] For example, the non-functional regions include a first target region requiring compressive stress and a second target region requiring tensile stress. The first target region includes a yellow area, and the second target region includes a blue area. The first target region is provided with a first type of isolation trench, and the second target region is provided with a second type of isolation trench. The depth of the first type of isolation trench is the same as the depth of the second type of isolation trench, but the types and quantities of stress-reducing materials filling the first type of isolation trench are different from those filling the second type of isolation trench. Specifically, the first type of isolation trench in the first target region is filled with two types of filling materials with tensile stress characteristics and one or more filling materials with compressive stress characteristics. The second type of isolation trench in the second target region is filled with two types of filling materials with compressive stress characteristics and one filling material with tensile stress characteristics. By setting the same depth in different regions of the wafer, the consistency of the processing can be improved, and the difficulty of the processing can be reduced. Simultaneously, by setting different types and quantities of stress-reducing materials in isolation trenches of the same depth in different regions, the warpage of different regions of the wafer can be adjusted, while reducing the difficulty of wafer processing and improving the efficiency of the wafer processing technology.

[0074] In some implementations, the orthographic projection shape of the isolation trench on the wafer includes a curved edge or a chamfered edge.

[0075] For example, the orthographic projection shape of the isolation trench on the wafer includes a circle, an ellipse, or a quadrilateral with rounded corners. By setting the edges of the isolation trench to curved or chamfered edges, it is beneficial for subsequent filling with filler material, and it can also avoid stress concentration on the wafer in sharp edge areas, thereby improving the reliability of wafer surface stress.

[0076] In some examples, both the first and second types of isolation trenches are discretely distributed. When the required stress type in the target area is tensile stress, the multiple first-type isolation trenches in the target area are not arranged continuously or connected to each other, but are distributed in a separated and independent manner in the target area. There is a gap between each first-type isolation trench, which is a non-isolation trench structure area, i.e., the wafer body material. When the required stress type in the target area is compressive stress, the multiple second-type isolation trenches in the target area are also discretely distributed in a separated and independent manner, with adjacent second-type isolation trenches separated by the wafer body material. By setting the isolation trenches as a discrete distribution rather than a continuous structure, each isolation trench independently undertakes the function of local stress regulation, which makes it easy to accurately control the overall stress magnitude and distribution pattern of the target area by adjusting the number, density, and spatial arrangement of the isolation trenches. On the other hand, the discrete distribution combined with a certain degree of disorder in the arrangement design effectively avoids the directional accumulation of stress in a specific direction, significantly reduces the risk of wafer mechanical damage caused by stress concentration, and improves process safety.

[0077] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0078] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

[0079] Although preferred embodiments have been described in this specification, 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 specification.

[0080] Obviously, those skilled in the art can make various modifications and variations to this specification without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims and their equivalents, this specification is also intended to include such modifications and variations.

Claims

1. A method for adjusting wafer warpage, characterized in that, include: Obtain the initial warpage distribution of the wafer; Based on the initial warpage distribution, the target area on the wafer that needs warpage adjustment and the type of stress required to adjust the warpage are determined. The stress type includes tensile stress and compressive stress. The tensile stress is used to reduce the radius of curvature of the wafer warpage, and the compressive stress is used to increase the radius of curvature of the wafer warpage. Based on the target area and the corresponding stress type, determine the number and size of the isolation grooves within the target area, as well as at least one type of filling material; Based on the target area and the number and size of the isolation trenches, isolation trenches are etched on the wafer; At least one of the filling materials is disposed within the isolation groove; The wafer containing the isolation groove and the filling material is annealed.

2. The method for controlling wafer warpage according to claim 1, characterized in that, The step of determining the number and size of isolation grooves and at least one type of filling material within the target area, based on the target area and the corresponding stress type, includes: Based on the target area and the corresponding stress type, at least one type of filling material is determined, wherein, when the stress type is tensile stress, the filling material includes at least a stress material with tensile stress characteristics; and when the stress type is compressive stress, the filling material includes at least a stress material with compressive stress characteristics.

3. The method for controlling wafer warpage according to claim 2, characterized in that, Based on the target area and the corresponding stress type, at least one type of filling material is determined, including: Based on the target area and the corresponding stress type, the type and thickness of the filling material are determined, wherein the type of the filling material includes compressive stress characteristic material and tensile stress characteristic material, the compressive stress characteristic material includes multiple types of materials, and the tensile stress characteristic material includes multiple types of materials; When the required stress type in the target area is tensile stress, the number and size of the isolation grooves in the target area are determined based on the fact that the sum of the stresses of the tensile stress characteristic materials in the isolation groove is greater than the sum of the stresses of the compressive stress characteristic materials. The sum of the stresses of the tensile stress characteristic materials is the sum of the products of the thickness of each tensile stress characteristic material and the stress value per unit thickness of the tensile stress characteristic material. The sum of the stresses of the compressive stress characteristic materials is the sum of the products of the thickness of each compressive stress characteristic material and the stress value per unit thickness of the compressive stress characteristic material. When the required stress type in the target area is compressive stress, the number and size of the isolation grooves in the target area are determined based on the fact that the sum of the stresses of the tensile stress characteristic materials set in the isolation groove is less than the sum of the stresses of the compressive stress characteristic materials.

4. The method for controlling wafer warpage according to claim 3, characterized in that, The step of determining the number and size of isolation grooves within the target area based on the type, quantity, and thickness of the filling material includes: If the filling material includes a type of stress material and the required stress type for the target area is tensile stress, then a first type of isolation groove is determined to be provided in the target area. When the filling material includes a type of stress material and the required stress type for the target area is compressive stress, a second type of isolation groove is provided in the target area; The diameter of the first type of isolation groove should be less than half the thickness of the tensile stress filling material, and the diameter of the second type of isolation groove should be less than half the thickness of the compressive stress filling material, so as to ensure that both the first type of isolation groove and the second type of isolation groove are filled with the corresponding stress material.

5. The method for controlling wafer warpage according to claim 4, characterized in that, Based on the type, quantity, and thickness of the filling material, the number and size of the isolation grooves to be set in the target area are determined, including: When the filling material includes multiple types and the required stress type for the target area is tensile stress, the thickness ratio of the multiple types of filling materials in the isolation groove is determined based on the fact that the sum of the stresses of the tensile stress characteristic materials in the first type of isolation groove is greater than the sum of the stresses of the compressive stress characteristic materials. The thickness ratio of the multiple stress characteristic materials filling the isolation groove is used to correspond to the stress type of the target area. When the filling material includes multiple types and the target area requires compressive stress, the thickness ratio of the multiple types of filling materials in the isolation groove is determined based on the fact that the sum of the stresses of the tensile stress characteristic materials in the second type of isolation groove is less than the sum of the stresses of the compressive stress characteristic materials. The diameter of the first type of isolation groove should be less than half of the sum of the thicknesses of all tensile stress filling materials, and the diameter of the second type of isolation groove should be less than half of the sum of the thicknesses of all compressive stress filling materials, so as to ensure that both the first type of isolation groove and the second type of isolation groove are filled with the corresponding stress materials.

6. The method for controlling wafer warpage according to claim 3, characterized in that, The target region includes a first target region and a second target region, and the method includes: When the filling material includes multiple types, a first type of isolation trench is prepared in the first target region by a first round of photolithography and etching processes; A second type of isolation trench is prepared in the second target region through a second round of photolithography and etching processes.

7. The method for controlling wafer warpage according to claim 1, characterized in that, The annealing process is performed at a temperature greater than the maximum stress release temperature among all stressed materials.

8. A wafer, characterized in that, The wafer is subjected to warpage adjustment using the method for adjusting wafer warpage as described in any one of claims 1 to 7, the wafer comprising: The device region and the non-functional region, wherein the non-functional region at least partially surrounds the device region, or the non-functional region and the device region are alternately arranged; An isolation groove is provided in the non-functional area; Filling material is placed inside the isolation groove.

9. The wafer according to claim 8, characterized in that, The non-functional area includes a first target area requiring compressive stress and a second target area requiring tensile stress. The isolation groove includes a first type of isolation groove and a second type of isolation groove. The first target area is provided with a first type of isolation groove, and the second target area is provided with a second type of isolation groove. Wherein, the type of stress material filling the first type of isolation groove is different from the type of stress material filling the second type of isolation groove; and / or, The number of different types of stress materials filling the first type of isolation groove is different from the number of different types of stress materials filling the second type of isolation groove.

10. The method for controlling wafer warpage according to claim 9, characterized in that, The stress material includes silicon dioxide and polycrystalline silicon; and / or, The orthographic projection shape of the isolation trench on the wafer includes curved edges or chamfered edges; and / or, The first type of isolation trenches are discretely distributed; and / or, The second type of isolation trenches are discretely distributed.

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