Wafer edge fixed-point spray leveling process based on trim height measurement

Abstract

The present application relates to chip packaging technical field, especially to a kind of wafer edge fixed-point spray leveling process based on Trim height measurement.The wafer with Trim structure on edge is prepared;Trim structure includes inside transition zone, middle low area and outside edge zone;Height measurement is carried out to Trim structure, to characterize the height distribution of Trim structure;According to height distribution, the characteristics of leveling material are determined, and then the spraying parameters are determined;According to the spraying parameters, leveling material is sprayed to Trim structure, leveling material covers Trim structure, leveling material after spraying is leveled, pre-baked and / or solidified, and leveling layer is formed on Trim structure.The present application can level wafer edge according to the height distribution of Trim structure, make leveling material cover Trim area, reduce the residual height difference after leveling, improve the surface flatness of wafer edge, and provide relatively gentle edge surface for subsequent wafer processing.

Description

Technical Field

[0001] This invention relates to the field of chip packaging technology, and in particular to a wafer edge point spraying and leveling process based on Trim height measurement. Background Technology

[0002] The current mainstream coating process is the Spin coating process, also known as spin coating, rotational coating, or uniform coating. This process uses the centrifugal force generated by high-speed rotation to prepare a uniform thin film on the substrate surface. Its working principle is as follows: liquid coating materials such as photoresist or sol are dropped onto the center of a stationary or slowly rotating substrate. Through high-speed rotation, the coating material diffuses outward and spreads evenly under the action of centrifugal force. As the solvent evaporates, a uniform thin film with a thickness of nanometers to micrometers is finally formed on the substrate surface.

[0003] This process is mainly suitable for planar or near-planar substrates, and it is difficult to effectively coat complex three-dimensional wafers with trim structures on the edges. Such wafers often have a height difference of less than 200μm.

[0004] When wafers with trim structures at the edges are used with traditional spin coating processes, the following technical problems are likely to occur: 1. Due to the significant structural drop, defects such as poor coating and abnormal film continuity are prone to occur in the trim area. If the poorly coated area extends beyond the sealing ring, it will cause the electroplating safety seal test to fail, and the equipment will not be able to operate normally; if the poorly coated area is located outside the sealing area, it will cause electroplating incomplete plating problems.

[0005] 2. The significant height difference in the Trim structure makes it easy for adhesive to accumulate at the edges during spin coating, resulting in excessive edge film thickness and interfering with the normal implementation of subsequent edge washing processes. Summary of the Invention

[0006] Purpose of the invention: In order to overcome the technical defects of the prior art, the present invention provides a wafer edge fixed-point spraying and leveling process based on Trim height measurement.

[0007] The technical solution of the present invention is as follows: A wafer edge-mounted spraying and leveling process based on trim height measurement includes the following steps: Prepare a wafer with a Trim structure at the edge; the Trim structure includes an inner transition region, a central depression region, and an outer edge region along the radial direction of the wafer from the wafer center to the outer periphery; wherein, the surface height of the inner transition region gradually decreases radially outward to the central depression region, the surface height of the central depression region is lower than the effective device surface of the wafer or the height measurement reference plane, and the outer edge region extends from the central depression region to the outer periphery of the wafer. The height of the Trim structure is measured to obtain the average and / or maximum height difference of the Trim structure relative to the effective device surface of the wafer or the height measurement reference plane, thus characterizing the height distribution of the Trim structure. The characteristics of the leveling material are determined based on the height distribution, and the spraying parameters are determined by combining the height distribution and the characteristics of the leveling material. The characteristics of the leveling material include viscosity and / or solid content, and the spraying parameters include at least one of nozzle distance, spraying width, spraying flow rate, and wafer rotation speed. The wafer is clamped on a rotating platform, and a leveling material is sprayed onto the Trim structure according to the spraying parameters. The leveling material covers the Trim structure. The sprayed leveling material is then leveled, pre-baked, and / or cured to form a leveling layer on the Trim structure.

[0008] Furthermore, obtaining the average height difference and / or maximum height difference of the Trim structure relative to the wafer's effective device surface or height measurement reference plane includes: obtaining the average height difference and / or maximum height difference of the inner transition region, the central depression region, and the outer edge region relative to the wafer's effective device surface or height measurement reference plane, respectively; the average height difference is the arithmetic mean of the height differences of each measurement point in the corresponding region relative to the wafer's effective device surface or height measurement reference plane, and the maximum height difference is the maximum value among the height differences of each measurement point in the corresponding region relative to the wafer's effective device surface or height measurement reference plane.

[0009] Furthermore, the leveling material includes a polyimide adhesive.

[0010] Furthermore, the Trim structure has a height difference relative to the effective device surface of the wafer or the height measurement reference plane, and the height difference is 50μm-200μm; the average height difference of the central depression area relative to the effective device surface of the wafer or the height measurement reference plane is 80μm-190μm, and the maximum height difference is 86μm-198μm.

[0011] It should be noted that the height difference of the Trim structure refers to the overall height difference formed by the Trim structure relative to the effective device surface of the wafer or the height measurement reference plane, which is used to characterize the overall morphological scale of the Trim structure to be processed. The height difference of the Trim structure applicable to this invention is 50μm-200μm.

[0012] When measuring the height of the Trim structure, the effective device surface of the wafer or a height measurement reference plane is used as the reference plane. Multiple measurement points are set at different locations on the Trim structure, and the height difference of each measurement point relative to the reference plane is obtained. Based on the height differences of each measurement point, the average height difference and the maximum height difference of the Trim structure are obtained to characterize the height distribution of the Trim structure. Since the surface height of the Trim structure is not completely uniform along the radial and circumferential directions, the average height difference can characterize the overall height variation of the corresponding area, and the maximum height difference can characterize the maximum local height variation of the corresponding area. The combination of the two can reflect the overall and local height distribution characteristics of the Trim structure.

[0013] In the specific implementation process, the average and maximum height differences of the inner transition zone, the central depression zone, and the outer edge zone can be obtained separately. Among them, the central depression zone is the main leveling area, and its average and maximum height differences can serve as important bases for determining the characteristics of the leveling material and spraying parameters. In the embodiment, the average and maximum height differences of the central depression zone are used to characterize the Trim structure at different initial height states.

[0014] Furthermore, the properties of the leveling material include viscosity and / or solids content, including: The viscosity of the leveling material at 25°C ranges from 80 cP to 300 cP, and the solid content of the leveling material ranges from 20 wt% to 50 wt%.

[0015] Spraying parameters include at least one of nozzle distance, spray width, spray flow rate, and wafer rotation speed, including: When spraying the leveling material, the nozzle distance includes the distance between the nozzle and the edge surface of the wafer, which includes 6mm-10mm; the spraying width includes 3mm-5mm; the spraying flow rate includes 0.03mL / s-0.10mL / s; and the wafer rotation speed during the spraying deposition stage includes 30rpm-150rpm.

[0016] Furthermore, the spraying of the leveling material includes the following steps: leveling the Trim structure by applying multiple thin-layer sprays, and performing pre-baking or leveling treatment between adjacent sprays.

[0017] Furthermore, the Trim structure after the formation of the leveling layer is retested to obtain the residual height difference of the Trim structure. When the residual height difference is greater than a preset threshold, local respraying is performed.

[0018] Preferably, before spraying the leveling material onto the Trim structure, a primer is first sprayed onto the Trim structure. The primer continuously covers the inner transition area, the central depression area, and the outer edge area, and the primer is pre-baked to form a continuous base layer. Subsequently, the leveling material is sprayed onto the continuous base layer. The leveling material is mainly deposited in the central depression area and extends towards the inner transition area and the outer edge area, respectively, forming a leveling layer on the continuous base layer.

[0019] It should be noted that the primer and the leveling material serve different purposes. The primer first covers the inner transition area, the central depression area, and the outer edge area of ​​the trim to improve the bonding strength between the leveling material and the wafer surface, and to reduce adhesive breakage or peeling at the trim sidewalls. The leveling material is sprayed on top of the primer and is mainly used to fill the central depression area and reduce the reduction in leveling layer thickness caused by pre-baking and curing.

[0020] Preferably, the preparation method of the primer material includes the following steps: Under nitrogen protection, 4,4'-diaminodiphenyl ether and diaminopropyl-terminated polydimethylsiloxane were added to N-methylpyrrolidone and stirred until dissolved. Then, pyromellitic dianhydride was added and the temperature was controlled. After the addition of materials is completed, stirring is continued for 8-12 hours under nitrogen protection; after the reaction is completed, some N-methylpyrrolidone is removed under reduced pressure, and the solid content and viscosity are adjusted to obtain polyamic acid solution. 3-Glycidyl etheroxypropyltrimethoxysilane was added to the polyamic acid adhesive solution, and after stirring, fumed silica was added. The mixture was then stirred and degassed under vacuum to obtain the primer material.

[0021] It should be noted that the primer material includes polyamic acid containing siloxane segments, 3-glycidyl etheroxypropyltrimethoxysilane, and fumed silica. This primer material is used to cover the trim area before applying the leveling material, forming a continuous base layer in the inner transition area, the central depression area, and the outer edge area, thereby improving the adhesion stability of the subsequent leveling material in the trim area.

[0022] In the preparation of polyamic acid containing siloxane segments, the terminal amino groups of diaminopropyl-terminated polydimethylsiloxane participate in the synthesis of polyamic acid, allowing the polydimethylsiloxane segments to enter the molecular structure of polyamic acid. During subsequent high-temperature curing, the polyamic acid undergoes imidization to form polyimide, and the polydimethylsiloxane segments can improve the flexibility of the cured primer. Therefore, the primer can mitigate the effects of pre-baking and curing shrinkage of the leveling material on the interface, reducing the likelihood of cracking or peeling of the leveling layer in the inner transition zone and sidewalls of the trim.

[0023] 3-Glycidyl etheroxypropyltrimethoxysilane contains a hydrolyzable trimethoxysilane group at one end and an epoxy group at the other. After oxygen plasma treatment, the wettability of the silicon wafer surface is improved, and it has more oxygen-containing groups. The trimethoxysilane group of 3-glycidyl etheroxypropyltrimethoxysilane, after hydrolysis, can combine with the oxygen-containing groups on the wafer surface; its epoxy group can react with amino, carboxyl, and other groups in the primer or leveling material. Through these effects, the bonding strength between the primer and the wafer surface, as well as between the primer and the leveling layer, can be improved, reducing the likelihood of the leveling layer detaching from the trim sidewalls.

[0024] Fumed silica is used to adjust the viscosity and flowability of the primer. The hydroxyl groups on the surface of fumed silica can interact with the polar groups in polyamic acid, preventing the primer from flowing excessively from the inclined trim sidewalls to the central depression area after spraying. Simultaneously, the small amount of fumed silica added does not hinder the primer from being sprayed through the nozzle or spreading on the trim surface. Therefore, the primer can form a thin and continuous base coat in the inner transition zone, the central depression area, and the outer edge area of ​​the trim.

[0025] By combining polyamic acid containing siloxane segments, 3-glycidoxypropyltrimethoxysilane, and fumed silica, the primer material can balance flexibility, adhesion, and flowability after spraying, providing a continuous and stable surface for subsequent leveling materials.

[0026] Preferably, the preparation method of the leveling material includes the following steps: Hollow silica particles were dried, cooled, and then added to anhydrous isopropanol. After stirring and ultrasonic treatment, a hollow silica dispersion was obtained. 3-Aminopropyltriethoxysilane was added to anhydrous isopropanol and stirred until homogeneous. Then it was added to the hollow silica dispersion and stirred. Hollow silica particles were separated, washed, and dried to obtain modified hollow silica particles. Under nitrogen protection, 4,4'-diaminodiphenyl ether was added to N-methylpyrrolidone and stirred until dissolved. Then, pyromellitic dianhydride was added in batches while controlling the temperature. After the addition was completed, stirring was continued for 8-12 hours under nitrogen protection. After the reaction was completed, some N-methylpyrrolidone was removed under reduced pressure, and the solid content and viscosity were adjusted to obtain polyamic acid solution. The modified hollow silica particles were dispersed in N-methylpyrrolidone to obtain a hollow silica dispersion. The hollow silica dispersion was added to the polyamic acid adhesive, followed by the addition of benzoxazine resin and fumed silica. After stirring and vacuum degassing, the leveling material was obtained.

[0027] It should be noted that the leveling material includes polyamic acid, amino-modified hollow silica particles, benzoxazine resin, and fumed silica. This leveling material is mainly sprayed onto the low-lying area in the center of the trim, extending towards the inner transition area and the outer edge area, to reduce the height difference in the trim area.

[0028] Hollow silica particles have internal cavities and are less prone to volume shrinkage during the pre-baking and curing processes of the leveling material. Dispersing hollow silica particles in polyamic acid can reduce the impact of shrinkage caused by solvent evaporation and imidization on the overall thickness of the leveling layer, thus minimizing the reduction in thickness after curing. Compared to solid silica particles, hollow silica particles have a lower apparent density and are less likely to settle significantly due to their own weight in the leveling material, which helps maintain the dispersion of the particles within the material.

[0029] Treating hollow silica particles with 3-aminopropyltriethoxysilane introduces amino groups onto the particle surface. These amino groups can react with or form hydrogen bonds with polar groups such as carboxyl and amide groups in polyamic acid, improving the compatibility between the hollow silica particles and polyamic acid and reducing particle agglomeration in the leveling material. Consequently, the hollow silica particles can be more uniformly dispersed in the leveling layer, reducing localized defects caused by uneven particle distribution.

[0030] During high-temperature curing, benzoxazine resin undergoes ring-opening polymerization to form a cross-linked structure. This cross-linked structure improves the strength and stability of the cured leveling layer and reduces deformation after curing. The curing of benzoxazine resin and the imidization of polyamic acid proceed gradually during the heating process, allowing the leveling material to achieve a certain degree of leveling before curing and gradually curing as the temperature rises, thereby maintaining the surface shape after leveling.

[0031] Fumed silica is used to adjust the viscosity and flowability of the leveling material after spraying. During spraying, the leveling material is atomized and deposited in the trim area by the nozzle. After spraying, fumed silica reduces the continued flow of the leveling material, making it less likely to flow out of the central depression area or excessively accumulate towards the outermost edge of the wafer. Therefore, the leveling material is primarily retained in the central depression area with the largest height deficiency, while also covering the adjacent inner transition area and outer edge area.

[0032] By combining polyamic acid, amino-modified hollow silica particles, benzoxazine resin and fumed silica, the leveling material can maintain sprayability while reducing excessive flow after spraying and thickness reduction after pre-baking and curing, thus ensuring that the leveling layer maintains a small residual height difference after curing.

[0033] Beneficial effects: 1. This invention measures the height of the trim structure at the wafer edge to obtain the average and / or maximum height difference of the trim structure relative to the effective device surface or a height measurement reference plane, characterizing the height distribution of the trim structure. Based on this height distribution, the viscosity and / or solid content of the leveling material are determined, further determining spraying parameters such as nozzle distance, spray width, spray flow rate, and wafer rotation speed, ensuring that the leveling material and spraying conditions match the actual height of the trim structure. Compared to directly spin-coating the entire wafer, this invention can directionally spray the leveling material to the trim area at the wafer edge, reducing ineffective coating of the leveling material on the effective device surface and lowering the possibility of the leveling material being thrown away from the low-lying area of ​​the trim during high-speed spin-coating.

[0034] 2. This invention addresses the morphological characteristics of the Trim structure, which sequentially forms an inner transition region, a central depression region, and an outer edge region along the wafer's radial direction. It ensures that the leveling material is primarily deposited in the central depression region, which has a lower surface height, a larger average height difference, and / or a larger maximum height difference, extending towards the inner transition region and the outer edge region. Simultaneously, the amount of material deposited near the outer perimeter of the wafer is controlled. This allows the leveling material to continuously cover the Trim sidewalls and the central depression region while reducing excessive accumulation of the leveling material at the outermost edge of the wafer. This improves the problems of exposed substrate, broken adhesive, and edge adhesive buildup that easily occur in the Trim region, resulting in a smoother wafer edge surface after leveling. This provides a more continuous surface for subsequent full-surface coating, electroplating sealing inspection, or electroplating processes.

[0035] 3. For trim structures with significant height differences, this invention employs multiple thin-layer sprayings, with leveling and / or pre-baking performed between adjacent sprayings. This allows the deposited layer formed by the previous spraying to achieve a certain degree of shape stability before subsequent sprayings. Compared to increasing the wet film thickness all at once, this method reduces the occurrence of sagging of the leveling material at the trim sidewalls and accumulation at the wafer edge, and lowers the risk of cracking or peeling of thick leveling materials during pre-baking and curing. It is suitable for wafer edge trim structures with height differences of 50μm-200μm.

[0036] 4. This invention re-inspects the height of the Trim structure after spraying and, based on the re-inspection results, performs low-flow re-spraying on circumferential local areas with large residual height differences. This method can specifically correct local areas with large residual height differences after the initial leveling without repeating the spraying of the entire Trim structure. This avoids further thickening of the leveling layer in other areas and reduces the residual height difference between different circumferential locations on the wafer, improving the consistency of wafer edge leveling.

[0037] 5. This invention further forms a continuous primer layer before the leveling material is sprayed. The primer layer can first cover the inner transition area, the central depression area, and the outer edge area, providing a continuous adhesion surface for the subsequent leveling material. The polyamic acid containing siloxane segments in the primer layer combines the heat resistance of polyimide and the flexibility of siloxane segments after curing, which can alleviate the interfacial stress between the silicon wafer and the thicker leveling layer; 3-glycidyl etheroxypropyltrimethoxysilane helps to improve the bonding between the primer layer and the oxygen plasma-treated wafer surface and the upper leveling material; fumed silica can regulate the flowability of the primer layer and reduce the excessive flow of the primer layer from the inclined trim sidewalls. Therefore, this primer layer helps to maintain continuous coverage at the trim sidewalls and reduces the possibility of film thinning, adhesive breakage, and sidewall peeling in the inner transition area.

[0038] 6. This invention employs a polyamic acid leveling material containing amino-modified hollow silica particles, benzoxazine resin, and fumed silica. Because hollow silica particles are less prone to volume shrinkage during pre-baking and curing, they reduce the impact of organic resin shrinkage on the overall thickness of the leveling layer. The amino groups on the surface of the hollow silica particles improve their compatibility and interfacial bonding with polyamic acid, resulting in more uniform dispersion of the hollow silica particles in the leveling layer. The benzoxazine resin undergoes ring-opening polymerization during curing, which helps improve the stability of the cured leveling layer. Fumed silica regulates the flowability of the leveling material after spraying, reducing excessive flow from the low-lying area in the center of the trim towards the outer edge of the wafer. The synergistic effect of these components reduces shrinkage during pre-baking and curing, as well as the reduction in thickness after curing, ensuring a smaller residual height difference in the trim area after curing.

[0039] 7. The primer and leveling material serve to cover the interface and compensate for height, respectively. The primer first forms a continuous adhesion interface on the trim structure, and then the leveling layer fills the central depression on the primer, creating a gradual transition between the wafer surface, the primer, and the leveling layer. This setup does not rely solely on increasing the amount of leveling material to fill the trim structure, but simultaneously improves trim sidewall adhesion, thick-layer curing shrinkage, and post-spraying shape retention, thereby achieving a continuous and stable leveling layer on trim structures with significant height differences. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1This is a schematic diagram of the wafer with a Trim structure at its edge, as described in this invention. Figure 2 This is a schematic diagram of the wafer structure after the leveling process is completed according to the present invention.

[0042] The diagram is labeled as follows: 1. Trim structure; 2. Effective device surface of wafer; 3. Leveling layer; 4. Inner transition region; 5. Central depression region; 6. Outer edge region. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, those skilled in the art can make adaptive adjustments to specific parameters, material types, equipment models and process sequences.

[0044] Method 1 This invention provides a wafer edge point spraying and leveling process based on Trim height measurement.

[0045] 1. Reference Figure 1 A wafer with a trim structure 1 at its edge is prepared as the wafer to be processed. The wafer with a trim structure 1 at its edge can be the wafer to be processed after front-end wafer fabrication or wafer-level packaging preprocessing. The wafer can first undergo conventional wafer fabrication, thinning, cleaning and other processes, and then, according to the subsequent packaging or edge processing requirements, the edge area of ​​the wafer is trimmed to form a stepped, sloping, recessed or complex height difference structure relative to the effective device surface 2 or reference plane of the wafer, thereby obtaining a wafer with a trim structure 1 at its edge.

[0046] The edge trimming process can be carried out by mechanical grinding, cutting wheel cutting, laser trimming, dry etching, wet etching, or a combination thereof, to remove material from the edge of the wafer and create a height difference in the outer periphery of the wafer.

[0047] 2. Clean the wafer to be processed. Perform oxygen plasma treatment on the trim area of ​​the wafer edge. It should be noted that oxygen plasma treatment is an optional step and can be performed or not depending on actual needs.

[0048] 3. Using laser confocal inspection equipment, spectral confocal displacement sensor, three-dimensional morphology inspection equipment, or a fully automated semiconductor microscope with automatic focusing height measurement, Z-axis displacement measurement, or multi-focal image reconstruction functions, the height of the wafer edge Trim structure 1 is measured to confirm the height difference of Trim structure 1. This invention's process is suitable for Trim structures 1 with a height difference of 50-200 μm, because when the height difference is less than 50 μm, the impact on the process is negligible. This negligibility is because when the height difference of the Trim structure reaches the aforementioned 50-200 μm range, its impact on subsequent coating continuity and edge morphology is more significant, and the point-spraying leveling method of this invention can achieve a more significant improvement effect.

[0049] 4. Reference Figure 2 Based on the measured height of the Trim structure 1, the average and maximum height differences of the Trim structure 1 relative to the effective device surface 2 of the wafer or the height measurement reference plane are obtained, characterizing the height distribution of the Trim structure 1. The properties of the leveling material are determined based on the height distribution, and the spraying parameters are determined based on the height distribution and the properties of the leveling material. The properties of the leveling material include viscosity and / or solid content; the spraying parameters include at least one of the following: distance between the nozzle and the wafer edge, spray width, spray flow rate, number of sprays, nozzle opening time, wafer rotation speed, and circumferential spraying angle range.

[0050] The purpose of leveling is not to form a uniform thickness of filler layer in the entire Trim area, but to make the leveling material cover different areas in the Trim and control the residual height difference of the Trim area within a preset range after curing.

[0051] For the Trim structure 1 with significant elevation differences, multiple thin-layer spraying is used for leveling, with pre-baking or leveling treatment between adjacent sprays. The deposition amount of each spray is controlled based on the thickness of the pre-baked layer formed after spraying, the amount of adhesive buildup at the edges, and the coverage of the step sidewalls. When a single spray cannot achieve the target leveling effect, the number of sprays is increased to gradually form a leveling layer 3, reducing sagging, adhesive buildup at the edges, cracking, or sidewall peeling caused by a single thick spray.

[0052] Specifically, the wafer is securely clamped onto the rotating platform using vacuum adsorption or a non-vacuum chuck. A leveling material is then applied to the trim area at the wafer edge using a spray-coating process. During the spray deposition stage, the wafer rotation speed is preferably 30 rpm-150 rpm; during the leveling stage after spraying, the wafer rotation speed is preferably 50 rpm-300 rpm. With the nozzle closed, the wafer can be rotated briefly at 300 rpm-1000 rpm to homogenize the edges or remove excess adhesive from non-target areas. The leveling material, under the influence of surface tension, adhesion, and the circumferential spreading effect generated by the low-speed rotation, covers different areas of the trim, forming a continuous leveling layer 3, which smooths the surface of the wafer edge area.

[0053] 5. After leveling, the wafer edge trim area is inspected again. Only if the inspection is qualified can the wafer proceed to the subsequent full-surface coating, electroplating sealing inspection, or electroplating process. The qualification criteria are: the residual height difference after leveling does not affect the subsequent process, and the leveling layer 3 continuously covers the trim area. No obvious exposure of the substrate, broken adhesive, cracks, sidewall peeling, or abnormal adhesive buildup on the outer periphery of the wafer that would affect the subsequent process are observed.

[0054] The following section details the implementation of method 1 described above, providing more detailed steps.

[0055] It should be noted that, in specific implementation, a wafer with Trim structure 1 at the edge, such as... Figure 1 As shown, the high-level flat region in the center of the wafer is the wafer's effective device surface 2 or the height measurement reference plane. The regions located on both sides of the high-level flat region and recessed downwards relative to the reference plane are called Trim regions. The Trim regions on the left and right sides are basically symmetrical with respect to the wafer center.

[0056] For any side of the Trim region, along the wafer radial direction from the wafer center to the outer periphery, it successively includes an inner transition region 4, a central depression region 5, and an outer edge region 6. The inner transition region 4 is adjacent to the wafer's effective device surface 2, and its surface height gradually decreases radially outward, transitioning from the higher position of the wafer's effective device surface 2 to the central depression region 5. The inclined or arc-shaped surface of the inner transition region 4 constitutes the Trim sidewall.

[0057] The central depression area 5 is located between the inner transition area 4 and the outer edge area 6. It is a region in the Trim region with a large height difference relative to the effective device surface 2 of the wafer or the height measurement reference plane, and the height change along the radial direction is relatively gentle. The central depression area 5 constitutes the main deposition area of ​​the leveling material.

[0058] The outer edge region 6 is located on the side of the central depression region 5 near the outer periphery of the wafer and extends to the outer periphery of the wafer. The outer edge region 6 may include an arc-shaped surface, a slope, or a locally raised surface that transitions from the central depression region 5 to the outer periphery of the wafer. Because the outer edge region 6 is close to the outer periphery of the wafer, the leveling material tends to accumulate in this area, therefore the amount of coating per unit area in the outer edge region 6 is less than that in the central depression region 5.

[0059] During the spraying and leveling process, the leveling material is mainly deposited in the central low-lying area 5, and gradually thins along the Trim sidewall of the inner transition area 4 towards the effective device surface 2 of the wafer; the leveling material also extends to the outer edge area 6, but its deposition at the outermost edge of the wafer is controlled to reduce edge adhesive buildup. After the leveling material cures, a leveling layer 3 is formed on the Trim structure 1.

[0060] More specifically, at any circumferential measurement position, using the wafer's effective device surface 2 or the height measurement reference plane as the reference plane, multiple measurement points are set along the wafer's radial direction to obtain the height difference between each measurement point and the reference plane, and the maximum height difference is determined. A continuous radial region where the height difference reaches 90% or more of the maximum height difference is defined as the central depression region 5; the region between the side of the central depression region 5 closest to the wafer center and the wafer's effective device surface is defined as the inner transition region 4; the region between the side of the central depression region 5 closest to the wafer's outer perimeter and the wafer's outer perimeter end face is defined as the outer edge region 6. The arithmetic mean and / or maximum value of the height differences between each measurement point in the inner transition region 4, the central depression region 5, and the outer edge region 6 relative to the reference plane are calculated respectively, and these are taken as the average height difference and / or maximum height difference of the corresponding regions.

[0061] The Trim structure of the wafer will not be repeated below.

[0062] Example 1 This embodiment provides a wafer edge point spraying and leveling process based on Trim height measurement.

[0063] 1. Prepare a wafer with a Trim structure 1 at its edge as the wafer to be processed. Specifically, the wafer is a 12-inch silicon wafer with a diameter of approximately 300 mm and a thickness of 775 μm. After the wafer edge is trimmed, a Trim structure 1 is formed within a range of approximately 2.0 mm to 5.0 mm from the outer periphery of the wafer. This Trim structure 1 has a height difference relative to the effective device surface 2 of the wafer.

[0064] 2. Clean the wafer to be processed. Specifically, place the wafer in a cleaning device, rinse with deionized water, and then dry with nitrogen. Perform oxygen plasma treatment on the wafer edge trim area. The oxygen plasma power is 100W, and the treatment time is 60 seconds to improve the wettability and adhesion of the subsequent polyimide adhesive on the trim area.

[0065] 3. The height of the wafer edge Trim structure 1 was measured using a laser confocal inspection device. During measurement, the effective device surface 2 of the wafer was used as the reference plane. A measurement angle was selected every 5° along the wafer circumference, and multiple measurement points were selected radially at each measurement angle. The measurement area covered a range of 0.5mm-8.0mm from the outer circumference of the wafer. The measurements showed that the average height difference of the inner transition region 4 of the Trim relative to the reference plane was 38μm, and the maximum height difference was 68μm. The average height difference of the low-lying region 5 in the middle of the Trim relative to the reference plane was 80μm, and the maximum height difference was 86μm. The average height difference of the outer edge region 6 of the Trim relative to the reference plane was 56μm, and the maximum height difference was 72μm.

[0066] 4. Based on the measured average and maximum height differences in the Trim area, and considering the solid content, viscosity, and single-pass deposition capacity of the polyimide adhesive used, it was determined that a thin-layer spraying method with two or more coats would be used for leveling. During the spraying process, the number of subsequent sprays and the spraying time were adjusted according to the leveling status after each spray, the coverage of the step sidewalls, and the deposition thickness after pre-baking, so that the leveling material was mainly deposited in the low-lying area in the middle of the Trim, avoiding the formation of abnormally thick adhesive at the outermost edge of the wafer.

[0067] Specifically, the wafer is fixed on the vacuum chuck of the rotating platform to keep it horizontal. The spray nozzle is positioned above the wafer edge, with the spray direction facing the trim area. The vertical distance between the nozzle and the wafer edge surface is 10 mm, and the spray width is 3 mm. The leveling material is a polyimide adhesive with a viscosity of 80 cP-150 cP and a solid content of 25 wt%-35 wt%.

[0068] During the spraying process, the wafer rotates at 80 rpm, and the spray nozzle sprays leveling material onto the trim area of ​​the wafer edge at a flow rate of 0.05 mL / s. During each round of spraying, the nozzle remains open while the wafer rotates continuously for several revolutions, ensuring uniform deposition of the leveling material along the circumference of the trim area. After one round of spraying, the wafer is rotated at 120 rpm for 20-30 seconds for initial leveling and then pre-baked at 100°C. The next round of spraying continues based on the height distribution of the trim area and the coverage of the leveling layer 3 after pre-baking. This embodiment involves two rounds of thin-layer spraying, with the nozzle opening time for each round adjusted according to the deposition thickness after pre-baking.

[0069] If subsequent processes require complete curing, it can be further cured at 300°C for 60 minutes under a nitrogen atmosphere.

[0070] After leveling is completed, the wafer edge trim area is inspected again using a three-dimensional morphology inspection device. Only when the inspection is qualified can the wafer proceed to the subsequent full-surface coating, electroplating sealing inspection or electroplating process.

[0071] Example 2 This embodiment provides a wafer edge point spraying and leveling process based on Trim height measurement.

[0072] 1. Prepare a wafer with a Trim structure 1 at its edge as the wafer to be processed. Specifically, the wafer is a 12-inch wafer with a diameter of approximately 300 mm and a thickness of 775 μm. The Trim structure 1 is located approximately 1.5 mm to 6.0 mm inward from the outer periphery of the wafer. This Trim structure 1 has a height difference relative to the effective device surface 2 of the wafer.

[0073] 2. Clean the wafer to be processed. Specifically, place the wafer in a cleaning device, rinse with deionized water, and then dry with nitrogen. Perform oxygen plasma treatment on the wafer edge trim area. The oxygen plasma power is 100W, and the treatment time is 60 seconds to improve the wettability and adhesion of the subsequent polyimide adhesive on the trim area.

[0074] 3. The height of the wafer edge Trim structure 1 was measured using a fully automated semiconductor microscope. During measurement, the effective device surface 2 of the wafer was used as the reference plane. A measurement angle was selected every 3° along the wafer circumference, and multiple measurement points were selected radially at each measurement angle. The measurement area covered a range of 0.5mm-8.0mm from the outer circumference of the wafer. The measurements showed that the average height difference of the inner transition region 4 of the Trim relative to the reference plane was 72μm, and the maximum height difference was 118μm. The average height difference of the central low-lying region 5 of the Trim relative to the reference plane was 140μm, and the maximum height difference was 152μm. The average height difference of the outer edge region 6 of the Trim relative to the reference plane was 98μm, and the maximum height difference was 132μm.

[0075] 4. The leveling material uses polyimide adhesive with a viscosity of 120 cP-250 cP and a solid content of 30 wt%-40 wt%.

[0076] The wafer is fixed on a vacuum adsorption chuck. During the spray deposition stage, the wafer rotates at a speed of 60 rpm to 100 rpm; the distance between the spray nozzle and the edge of the wafer is 8 mm, the spray width is 4 mm, and the spray flow rate is 0.06 mL / s to 0.08 mL / s.

[0077] The coating process employs a multi-stage spraying method: The first spray primarily covers the central low-lying area 5 of the Trim. With the nozzle open, the wafer is continuously rotated several times to form a thin leveling layer 3 in the central low-lying area 5. After the first spray, the wafer is rotated at 120 rpm for 20 seconds for initial leveling and then pre-baked at a low temperature. The second spray covers the central low-lying area 5 of the Trim and extends towards the inner transition area 4 and the outer edge area 6. The nozzle opening time in the central low-lying area 5 is longer than that in the transition areas on both sides. After spraying, the wafer continues to level at 120-150 rpm for 30 seconds. The third spray is a supplementary spray only on the circumferential local area corresponding to the maximum height difference in the height distribution.

[0078] After spraying, the wafer is placed on a hot plate for stepped baking. First, it is baked at 90°C for 3 minutes to allow the solvent to evaporate slowly; then it is baked at 120°C for 5 minutes to improve the shape stability of the leveling layer 3; and then baked at 200°C for 20 minutes. If the leveling layer 3 is used as a permanent dielectric layer, it is further cured at 320°C for 60 minutes in a nitrogen atmosphere.

[0079] After leveling, a retest is conducted. Only when the retest is passed can the wafer proceed to the subsequent full-surface coating, electroplating sealing test, or electroplating process.

[0080] Example 3 This embodiment provides a wafer edge point spraying and leveling process based on Trim height measurement.

[0081] 1. Prepare a wafer with a Trim structure 1 at its edge as the wafer to be processed. Specifically, the wafer is a 12-inch silicon wafer with a diameter of approximately 300 mm and a thickness of 775 μm. The Trim structure 1 is located in the range of approximately 2.0 mm to 8.0 mm from the outer periphery of the wafer.

[0082] 2. Clean the wafer to be processed. Specifically, place the wafer in a cleaning device, rinse with deionized water, and then dry with nitrogen. Perform oxygen plasma treatment on the wafer edge trim area. The oxygen plasma power is 100W, and the treatment time is 60 seconds to improve the wettability and adhesion of the subsequent polyimide adhesive on the trim area.

[0083] 3. The height of the Trim structure 1 was measured using a laser confocal imaging device to obtain a three-dimensional height distribution map of the Trim region. Measurements showed that the average height difference between the inner transition zone 4 of the Trim and the reference plane was 105 μm, with a maximum height difference of 162 μm. The average height difference between the central low-lying area 5 of the Trim and the reference plane was 190 μm, with a maximum height difference of 198 μm. The average height difference between the outer edge area 6 of the Trim and the reference plane was 136 μm, with a maximum height difference of 178 μm.

[0084] Since the height difference of Trim structure 1 in this embodiment is large, if too much leveling material is sprayed at once, it is easy to cause local sagging, edge glue buildup or uneven curing shrinkage. Therefore, a combination of multiple thin-layer spraying and intermediate pre-baking is used to gradually level the material.

[0085] 4. The leveling material is made of polyimide liquid with a viscosity of 150 cP-300 cP and a solid content of 35 wt%-45 wt%.

[0086] The wafer is fixed on a rotating platform, and the wafer rotation speed is 50 rpm-80 rpm during the spray deposition stage. The distance between the spray nozzle and the edge surface of the wafer is 6 mm, the spray width is 5 mm, and the spray flow rate is 0.08 mL / s-0.10 mL / s.

[0087] After the first coating, pre-bake at 100℃ for 3 minutes; after the second coating, pre-bake at 110℃ for 5 minutes; after the third coating, pre-bake at 120℃ for 5 minutes; after the fourth coating, rotate the wafer at 150rpm-200rpm for 60 seconds to ensure thorough leveling. The thickness of the deposited layer formed after each coating and pre-bake is 15μm-40μm, reducing the risk of sagging and edge buildup caused by a single thick coating.

[0088] If the leveling layer 3 is used as a permanent substrate layer, then a final curing process is performed. The curing process includes: baking at 100°C for 5 minutes, baking at 180°C for 20 minutes, baking at 250°C for 30 minutes, and curing at 320°C for 60 minutes under a nitrogen atmosphere.

[0089] After leveling, a three-dimensional morphology inspection device is used for retesting. Only when the retest is qualified can the wafer enter the subsequent whole-surface coating, electroplating sealing inspection or electroplating process.

[0090] Comparative Example 1 This comparative example uses a traditional full-surface spin coating process to process a wafer with a Trim structure 1 at the edge.

[0091] 1. Prepare a wafer with a Trim structure 1 at the edge as the wafer to be processed. Specifically, the wafer is a 12-inch wafer with a diameter of approximately 300 mm and a Trim height difference of approximately 100 μm.

[0092] 2. Select polyimide liquid as the leveling material, drop the leveling material onto the center of the wafer, and then spin-coat the entire surface at 1500rpm-3000rpm. After spin-coating, pre-bake and cure.

[0093] Due to the significant elevation difference in the trim area at the wafer edge, the polyimide adhesive is rapidly ejected outwards under the centrifugal force of high-speed rotation. This makes it difficult to achieve stable coverage of the trim step sidewalls and low-lying areas, leading to discontinuous film layers or exposed substrate in some areas. Simultaneously, some adhesive accumulates at the trim step edges and the outer periphery of the wafer, forming thick edge adhesive. This thick edge adhesive may interfere with subsequent edge washing processes, and poor localized coating in the trim area may also lead to abnormal sealing tests or the risk of incomplete electroplating.

[0094] Compared with Comparative Example 1, the embodiment of the present invention first measures the height of the Trim structure, characterizes the height distribution of the Trim structure based on the average height difference and the maximum height difference, determines the characteristics of the leveling material and the corresponding spraying parameters based on the height distribution, and then directly levels the Trim area by using a Spray point spraying method. Therefore, it is possible to match the characteristics of the leveling material and the spraying process with the actual height state of the Trim structure.

[0095] Furthermore, for Trim structures 1 with a height difference of 50μm-200μm, if only ordinary polyimide adhesive is used for spraying and leveling, problems such as solvent evaporation shrinkage, resin curing shrinkage, sidewall sagging of Trim structure 1, adhesive buildup at the wafer edge, and stress concentration at the interface of leveling layer 3 are prone to occur during spraying, leveling, pre-baking, and curing. Especially for Trim structures 1 with a height difference greater than 160μm, simply increasing the number of spraying passes or increasing the wet film thickness can easily lead to cracking of leveling layer 3, sidewall peeling, or an increase in the residual height difference after curing.

[0096] To address the aforementioned issues, this invention further improves the leveling material.

[0097] It should be noted that in Example 6 and Comparative Example 2 below, the inner transition area, the middle low-lying area, and the outer edge area use the same average elevation difference and maximum elevation difference data as in Example 3.

[0098] The above settings do not imply that Examples 3, 6, and Comparative Example 2 were performed using the same wafer repeatedly. Instead, different wafer samples with matching initial trim height distributions were selected. Example 3 specifically illustrates the process implementation of multiple thin-layer point spraying using ordinary polyimide adhesive under conditions of large height difference trim structures. It mainly discloses the corresponding material parameters, spraying parameters, and process flow. Example 6, under the condition of having the same or basically the same initial trim height distribution as Example 3, further uses a layered material composed of a primer and a leveling material. Comparative Example 2 uses Example 6 as a direct control. While maintaining the initial trim structure, spraying process, total solids supply, pre-baking, touch-up spraying, and curing conditions basically the same, it replaces the primer and leveling material in Example 6 with a conventional polyimide precursor adhesive to compare the influence of different material systems on the leveling effect. Therefore, Example 3 mainly illustrates the basic spraying implementation under conditions of large height difference, while Example 6 and Comparative Example 2 are used to verify the technical effects produced by the layered material system.

[0099] Example 4 The specific steps for preparing the primer material are as follows: 1. Prepare the ingredients: 4,4'-Diaminodiphenyl ether: purity 98%; Pyromellitic dianhydride: purity 98%; Diaminopropyl-terminated polydimethylsiloxane: Sigma-Aldrich product, product number 481688, Poly(dimethylsiloxane), bis(3-aminopropyl) terminated, number average molecular weight approximately 2500; N-Methylpyrrolidone: Anhydrous grade, purity 99.5%; 3-Glycidyl etheroxypropyltrimethoxysilane: purity 98%; Fumed silica: HDK® N20 from Wacker.

[0100] The following preparation will be carried out using the prepared raw materials: 2. Preparation of the first polyamic acid adhesive solution Nitrogen gas was introduced into a dry three-necked flask, followed by the addition of 144 g of N-methylpyrrolidone, 11.4 g of 4,4'-diaminodiphenyl ether, and 0.6 g of diaminopropyl-terminated polydimethylsiloxane. The mixture was stirred until dissolved at room temperature. Subsequently, 13.08 g of pyromellitic dianhydride was added in batches, controlling the system temperature to not exceed 30°C during the addition process. After the addition was complete, stirring was continued for 8-12 hours under nitrogen protection to obtain a polyamic acid solution containing siloxane segments.

[0101] After the reaction was completed, some N-methylpyrrolidone was removed under reduced pressure below 50°C, and the solid content of the polyamic acid solution was adjusted to 23wt%, and the viscosity at 25°C was 100cP. This solution was named the first polyamic acid solution.

[0102] 3. Preparation of primer material Weigh 100g of the first polyamic acid adhesive solution and add 0.5g of 3-glycidyl etheroxypropyltrimethoxysilane. Stir at 300rpm for 45min at room temperature. Then add 0.1g of fumed silica and continue stirring for 30min. Finally, degas under vacuum at -0.09MPa for 17min to obtain the primer material. The obtained primer material has a viscosity of 118cP at 25℃ and a solid content of approximately 23.5wt%.

[0103] Example 5 The specific steps for preparing the leveling material are as follows: 1. Prepare the ingredients: 4,4'-Diaminodiphenyl ether: purity 98%; Pyromellitic dianhydride: purity 98%; N-Methylpyrrolidone: Anhydrous grade, purity 99.5%; Benzoxazine resin: JBZ-OP100I from JFE Chemical Corporation was used.

[0104] Hollow silica particles: Hollow Silica Nanoparticles from Nanochemazone, product number NCZ-NP-433 / 23, are used. They are in powder form, with a purity of not less than 99% and a particle size of 90nm. 3-Aminopropyltriethoxysilane: 99% purity; Fumed silica: HDK® N20 from Wacker. Isopropanol: analytical grade.

[0105] The following preparation will be carried out using the prepared raw materials: 2. Surface treatment with hollow silica particles Weigh 5.0 g of hollow silica particles, vacuum dry them at 120 °C for 4 h, cool them to room temperature, add them to 100 mL of anhydrous isopropanol, stir at 500 rpm for 30 min, and ultrasonically disperse them for 20 min to obtain a hollow silica dispersion.

[0106] Weigh 0.3 g of 3-aminopropyltriethoxysilane and add it to 20 mL of anhydrous isopropanol. After stirring until homogeneous, slowly add the mixture to the above hollow silica dispersion and stir at room temperature for 2 h. Subsequently, collect the hollow silica particles by centrifugation or filtration and wash them twice with anhydrous isopropanol. The washed particles are then vacuum dried at 80 °C for 6 h to obtain amino-modified hollow silica particles.

[0107] 3. Preparation of the second polyamic acid adhesive solution Nitrogen gas was bubbled through a dry three-necked flask, and 120 g of N-methylpyrrolidone and 10.0 g of 4,4'-diaminodiphenyl ether were added. The mixture was stirred at room temperature until completely dissolved. Subsequently, 10.9 g of pyromellitic dianhydride was added in batches, controlling the system temperature to not exceed 30°C during the addition process. After the addition was complete, stirring was continued for 8-12 hours under nitrogen protection to obtain a polyamic acid resin.

[0108] After the reaction was completed, some N-methylpyrrolidone was removed under reduced pressure below 50°C, and the solid content of the polyamic acid solution was adjusted to 28wt%, and the viscosity at 25°C was 225cP. This solution was named the second polyamic acid solution.

[0109] 4. Preparation of leveling material Weigh 5g of amino-modified hollow silica particles and add them to 15g of N-methylpyrrolidone. Stir at 500rpm for 30min and then sonicate for 20min to obtain a hollow silica dispersion.

[0110] Weigh 100g of the second polyamic acid solution and place it in a brown glass bottle. Stir at 300rpm at room temperature. Slowly add the hollow silica dispersion to the second polyamic acid solution while stirring. After the addition is complete, continue stirring at 500rpm for 60min.

[0111] Then, 5g of benzoxazine resin was added, and stirring was continued for 60 minutes. Next, 0.3g of fumed silica was weighed and added to the mixed adhesive solution in three portions, stirring for 10 minutes after each addition. After all the silica was added, stirring was continued for 40 minutes. The mixed adhesive solution was then placed in a vacuum degassing device and degassed at -0.09MPa for 20 minutes to obtain the leveling material.

[0112] The resulting leveling material has a viscosity of 265 cP at 25°C and a solid content of approximately 30.6 wt%.

[0113] Example 6 This embodiment provides a wafer edge point spraying and leveling process based on Trim height measurement.

[0114] 1. Prepare a wafer with a Trim structure 1 at its edge as the wafer to be processed. Specifically, the wafer is a 12-inch silicon wafer with a diameter of approximately 300 mm and a thickness of 775 μm. The Trim structure 1 is located in the range of approximately 2.0 mm to 8.0 mm from the outer periphery of the wafer.

[0115] 2. Clean the wafer to be processed. Specifically, place the wafer in a cleaning device, rinse with deionized water, and then dry with nitrogen. Perform oxygen plasma treatment on the wafer edge trim area. The oxygen plasma power is 100W, and the treatment time is 60 seconds to improve the wettability and adhesion of subsequent leveling materials in the trim area.

[0116] 3. The height of the Trim structure 1 was measured using a laser confocal imaging device to obtain a three-dimensional height distribution map of the Trim region. Measurements showed that the average height difference between the inner transition zone 4 of the Trim and the reference plane was 105 μm, with a maximum height difference of 162 μm. The average height difference between the central low-lying area 5 of the Trim and the reference plane was 190 μm, with a maximum height difference of 198 μm. The average height difference between the outer edge area 6 of the Trim and the reference plane was 136 μm, with a maximum height difference of 178 μm.

[0117] 4. Apply primer. Using the primer material prepared in Example 4, the first layer of the primer material is sprayed onto the Trim region at the edge of the wafer, so that the primer material continuously covers the inner transition region 4, the central depression region 5 and the outer edge region 6, forming a continuous primer layer.

[0118] During the spray deposition stage, the wafer rotation speed is 50 rpm-100 rpm, the distance between the spray nozzle and the wafer edge surface is 6 mm-10 mm, the spray width is 3 mm-5 mm, and the spray flow rate is 0.03 mL / s-0.06 mL / s. After spraying, pre-baking is carried out at 90℃-110℃ for 3 min-8 min.

[0119] 5. Spraying leveling material The leveling material prepared in Example 5 was used to apply a second layer to the Trim area. The leveling material was mainly deposited in the central depression area 5 and extended towards the inner transition area 4 and the outer edge area 6, respectively.

[0120] During the spray deposition stage, the wafer rotation speed is 50rpm-80rpm, the distance between the spray nozzle and the wafer edge surface is 6mm, the spray width is 5mm, and the spray flow rate is 0.06mL / s-0.10mL / s.

[0121] The second coating is applied using a multi-layer thin-coat method. After the first coat, it is pre-baked at 100°C for 3 minutes; after the second coat, it is pre-baked at 110°C for 5 minutes; after the third coat, the wafer is rotated at 150-200 rpm for 60 seconds to level, followed by pre-baking at 120°C for 5 minutes. This reduces the risk of sagging and edge buildup caused by a single thick coat.

[0122] 6. Retesting and touch-up spraying After spraying, the trim area is re-measured using a 3D morphology inspection device. If the re-measurement reveals that the residual height difference in the trim area is still greater than 15 μm, a low-flow-rate re-spray is performed based on the residual height difference. During the re-spray, the wafer rotation speed is 50 rpm-80 rpm, and the spray flow rate is 0.03 mL / s-0.04 mL / s. After the re-spray, the wafer is pre-baked at 100℃ to 120℃ for 3 min-8 min.

[0123] 7. Final curing After the touch-up spraying is completed, a step curing process is performed. The curing process includes: baking at 100℃ for 5 minutes, baking at 180℃ for 20 minutes, baking at 250℃ for 30 minutes, and curing at 320℃ for 60 minutes under a nitrogen atmosphere, so that the polyamic acid is converted into polyimide, and at the same time the benzoxazine resin undergoes ring-opening polymerization to form the leveling layer 3.

[0124] Comparative Example 2 The main difference between this comparative example and Example 6 is that the primer material prepared in Example 4 was replaced with a polyimide precursor adhesive, and the leveling material prepared in Example 5 was replaced with a polyimide precursor adhesive. All other conditions were the same as in Example 6. The polyimide precursor adhesive used was HD MicroSystems™ PI 2611 polyimide precursor adhesive. The specific steps are as follows: 1. Prepare a 12-inch silicon wafer with the same specifications as in Example 6. The Trim structure 1 is located approximately 2.0mm-8.0mm inward from the outer periphery of the wafer. Laser confocal analysis shows that the average height difference of the inner transition region 4 of the Trim relative to the reference plane is 105μm, and the maximum height difference is 162μm. The average height difference of the central depression region 5 of the Trim relative to the reference plane is approximately 190μm, and the maximum height difference is approximately 198μm. The average height difference of the outer edge region 6 of the Trim relative to the reference plane is 136μm, and the maximum height difference is 178μm.

[0125] 2. The wafer was cleaned with deionized water and dried with nitrogen gas, and then the Trim area was treated with oxygen plasma at 100W for 60 seconds.

[0126] 3. Polyimide precursor adhesive was used as the first and second layer spraying materials. Before spraying, the polyimide precursor adhesive was brought back to room temperature and stirred and vacuum degassed. According to the atomization requirements of the spraying equipment, the polyimide precursor adhesive was diluted with N-methylpyrrolidone, adjusting the viscosity of the diluted adhesive at 25°C to 240-300 cP. The actual solid content of the diluted adhesive was measured, and the nozzle opening time was determined based on the measured solid content. Based on the actual solid supply of the primer and leveling material in Example 6, the supply of the diluted polyimide precursor adhesive was adjusted to keep the total solid supply of both as consistent as possible.

[0127] 4. Apply the first layer of diluted polyimide precursor adhesive to the entire Trim area, continuously covering the inner transition area 4, the central low-lying area 5, and the outer edge area 6. During spraying, the wafer rotation speed is 50-100 rpm, the distance between the nozzle and the wafer edge surface is 6 mm-10 mm, the spray width is 3 mm-5 mm, and the spray flow rate is 0.03 mL / s-0.06 mL / s. After spraying, rotate the wafer at 100-150 rpm for 20-40 seconds to level it, and then pre-bake it at 90℃-110℃ for 3-8 minutes.

[0128] 5. Continue with the diluted polyimide precursor adhesive for the second layer of multiple thin-layer spraying. The sprayed material is mainly deposited in the central low-lying area 5, extending towards the inner transition area 4 and the outer edge area 6. The wafer rotation speed is 50rpm-80rpm, the distance between the nozzle and the wafer edge surface is 6mm, the spray width is 5mm, and the spray flow rate is 0.06mL / s-0.10mL / s.

[0129] After the first coating, the wafer is rotated at 120 rpm for 30 seconds to level, and then pre-baked at 100°C for 3 minutes. After the second coating, the wafer is rotated at 150 rpm for 40 seconds to level, and then pre-baked at 110°C for 5 minutes. After the third coating, the wafer is rotated at 150 rpm to 200 rpm for 60 seconds to level, and then pre-baked at 120°C for 5 minutes.

[0130] 6. Re-measurement was performed using a three-dimensional morphology inspection device. When the residual height difference in a local area exceeded 15 μm, local touch-up spraying was performed using diluted polyimide precursor adhesive. During touch-up spraying, the wafer rotation speed was 50 rpm-80 rpm, the spraying flow rate was 0.03 mL / s-0.04 mL / s, and the wafer was pre-baked at 100℃-120℃ for 3 min-8 min after touch-up spraying.

[0131] 7. After spraying, bake at 100℃ for 5 minutes, at 180℃ for 20 minutes, and at 250℃ for 30 minutes in sequence, and then cure at 320℃ for 60 minutes under nitrogen atmosphere to form leveling layer 3.

[0132] Detection To verify the leveling effect of the present invention, leveling effect tests were conducted on Example 6 and Comparative Example 2. For Example 6 and Comparative Example 2, wafers with the same or essentially identical initial trim height distribution were selected as test samples. Except for the material systems to be compared, the spraying process, total solids supply, pre-baking conditions, touch-up spraying conditions, and final curing conditions were kept as consistent as possible. One wafer was taken from each group for testing. Measurements were taken at four circumferential positions (0°, 90°, 180°, and 270°) along the circumference of each wafer, and the arithmetic mean of the test results at the four circumferential positions was calculated.

[0133] 1. Residual height difference test A laser confocal inspection device was used to measure the central depression area 5 of the trim before and after leveling. Before leveling, the effective device surface 2 of the wafer was used as a reference plane, and the initial height difference of the central depression area 5 relative to the reference plane was measured at four circumferential positions: 0°, 90°, 180°, and 270°. After leveling and curing, the remaining height difference of the central depression area 5 relative to the reference plane was measured again at the same circumferential positions, and the remaining height difference was taken as the residual height difference at the corresponding circumferential position. At each circumferential position, multiple measurement points were set radially along the central depression area 5, and the arithmetic mean of the height differences of each measurement point relative to the reference plane was taken as the residual height difference at that circumferential position.

[0134] It should be noted that the residual height difference is mainly measured and evaluated for the central depression area 5 of the Trim. This is because the central depression area 5 is the region in the Trim structure with a large height difference relative to the reference plane and plays a major role in height compensation. The leveling material is also mainly deposited in this region. Therefore, the residual height difference of the central depression area 5 after leveling, relative to the reference plane, can directly reflect the height compensation effect of this invention on the main depression area of ​​the Trim. In contrast, the inner transition area 4 and the outer edge area 6 are regions that transition from the wafer's effective device surface 2 to the central depression area 5 and from the central depression area 5 to the outer peripheral end face of the wafer, respectively. Their surfaces themselves have tilted, arc-shaped, or other height gradient characteristics. Including the inherent height changes of these regions in the residual height difference statistics will affect the evaluation of the main height compensation effect. Therefore, for the inner transition area 4 and the outer edge area 6, their leveling status is mainly evaluated by whether the leveling layer continuously covers the area and whether there are phenomena such as film thinning, adhesive breakage, sidewall peeling, or abnormal adhesive buildup at the edges.

[0135] The results are shown in Table 1.

[0136] Table 1

[0137] 2. Observation of appearance and continuous coverage The leveling status of Trim structure 1 was observed using a fully automated semiconductor microscope, and the presence of exposed substrate, broken adhesive, sidewall peeling, and abnormal adhesive buildup at the edges was recorded.

[0138] If the inner transition zone 4, the central depression zone 5, and the outer edge zone 6 of the Trim are all continuously covered by the leveling layer 3, and no obvious film breakage or substrate exposure is observed, it is evaluated as continuous coverage; if the film layer becomes thinner, the film breaks, or the substrate is exposed in a local location, it is evaluated as local discontinuity.

[0139] The results are as follows: Example 6: Continuous coverage, with no obvious glue breakage, exposed substrate, or sidewall peeling observed; Comparative Example 2: The inner transition zone 4 is thinned, and some areas show glue breakage.

[0140] Analysis: In Example 6, the average height difference in the low-lying area 5 of the Trim before leveling was approximately 190 μm, and the maximum height difference was approximately 198 μm. After layered, targeted spraying of primer and leveling material, multiple thin-layer depositions, re-measurement and re-spraying, and step-curing, the residual height differences at the four measurement positions of 0°, 90°, 180°, and 270° were 10.4 μm, 11.2 μm, 10.1 μm, and 11.0 μm, respectively, with an average residual height difference of 10.7 μm. The residual height differences at all four positions were less than 15 μm, and the difference between the maximum and minimum values ​​was only 1.1 μm. This indicates that Example 6 can not only reduce the height difference in the Trim area but also achieve a relatively consistent leveling effect at different positions along the wafer circumference.

[0141] Comparative Example 2 used a conventional polyimide precursor adhesive to replace the primer and leveling material in Example 6, while maintaining consistency in the spraying process, total solids supply, pre-baking conditions, touch-up spraying conditions, and final curing conditions as much as possible. The residual height differences at four measurement positions (0°, 90°, 180°, and 270°) in Comparative Example 2 were 32.8 μm, 36.5 μm, 34.1 μm, and 34.7 μm, respectively, with an average residual height difference of 34.5 μm, significantly higher than the 10.7 μm in Example 6. Compared to Comparative Example 2, the average residual height difference in Example 6 was reduced by approximately 69.0%, indicating that the leveling effect achieved in Example 6 was not solely due to multiple sprays or increased solids supply, but was closely related to the layered material system formed by the primer and leveling material.

[0142] Microscopic observations showed that the leveling layer 3 formed in Example 6 continuously covered the inner transition region 4, the central depression region 5, and the outer edge region 6 of the trim, without any obvious adhesive breakage, substrate exposure, or sidewall peeling. In contrast, Comparative Example 2 showed localized film thinning in the inner transition region 4, with adhesive breakage in some areas. The inner transition region 4 is located between the effective device surface 2 of the wafer and the central depression region 5 of the trim, and its surface height varies significantly, making it an area where the leveling material is prone to shrinkage, sagging, and interface detachment. The fact that Example 6 was able to maintain continuous coverage in this area indicates that its layered material system is superior to a single conventional polyimide precursor liquid in terms of trim sidewall wetting, interface bonding, and shape retention.

[0143] Based on the combined results of residual height difference and microscopic observation, it can be seen that even when using a process similar to that of Example 6, such as spot spraying, multiple thin-layer spraying, pre-baking, touch-up spraying, and curing, conventional polyimide precursor adhesives still exhibit significant height drop and localized discontinuities in coverage after curing. Example 6, through the coordinated efforts of the base coating and leveling layer 3, simultaneously achieves height compensation and continuous coverage on the Trim structure 1 with a height difference of approximately 200 μm. This meets the preset leveling requirement of a residual height difference of no more than 15 μm, providing a smoother and more continuous edge surface for subsequent wafer coating, sealing inspection, or electroplating processes.

[0144] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A wafer edge-point spraying and leveling process based on trim height measurement, characterized in that, Includes the following steps: Prepare a wafer with a Trim structure at the edge; the Trim structure includes an inner transition region, a central depression region, and an outer edge region along the radial direction of the wafer from the wafer center to the outer periphery; wherein, the surface height of the inner transition region gradually decreases radially outward to the central depression region, the surface height of the central depression region is lower than the effective device surface of the wafer or the height measurement reference plane, and the outer edge region extends from the central depression region to the outer periphery of the wafer. The height of the Trim structure is measured to obtain the average and / or maximum height difference of the Trim structure relative to the effective device surface of the wafer or the height measurement reference plane, thus characterizing the height distribution of the Trim structure. The characteristics of the leveling material are determined based on the height distribution, and the spraying parameters are determined by combining the height distribution and the characteristics of the leveling material. The characteristics of the leveling material include viscosity and / or solid content, and the spraying parameters include at least one of nozzle distance, spraying width, spraying flow rate, and wafer rotation speed. The wafer is clamped on a rotating platform, and a leveling material is sprayed onto the Trim structure according to the spraying parameters. The leveling material covers the Trim structure. The sprayed leveling material is then leveled, pre-baked, and / or cured to form a leveling layer on the Trim structure.

2. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 1, characterized in that, Obtaining the average and / or maximum height difference of the Trim structure relative to the wafer's effective device surface or height measurement reference plane includes: obtaining the average and / or maximum height difference of the inner transition region, the central depression region, and the outer edge region relative to the wafer's effective device surface or height measurement reference plane, respectively; the average height difference is the arithmetic mean of the height differences of each measurement point in the corresponding region relative to the wafer's effective device surface or height measurement reference plane, and the maximum height difference is the maximum value among the height differences of each measurement point in the corresponding region relative to the wafer's effective device surface or height measurement reference plane.

3. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 1, characterized in that, The leveling material includes polyimide liquid.

4. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 2, characterized in that, The Trim structure has a height difference relative to the effective device surface of the wafer or the height measurement reference plane, and the height difference is 50μm-200μm; the average height difference of the central depression area relative to the effective device surface of the wafer or the height measurement reference plane is 80μm-190μm, and the maximum height difference is 86μm-198μm.

5. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 4, characterized in that, The properties of the leveling material include viscosity and / or solids content, and the spraying parameters include at least one of nozzle distance, spray width, spray flow rate, and wafer rotation speed, including: The leveling material has a viscosity of 80 cP-300 cP at 25°C and a solid content of 20 wt%-50 wt%. When spraying the leveling material, the distance between the nozzle and the edge surface of the wafer is 6 mm-10 mm, the spraying width is 3 mm-5 mm, the spraying flow rate is 0.03 mL / s-0.10 mL / s, and the wafer rotation speed during the spraying deposition stage is 30 rpm-150 rpm.

6. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 1, characterized in that, The steps of spraying the leveling material include: leveling the Trim structure by spraying multiple thin layers, and performing pre-baking or leveling treatment between adjacent sprayings.

7. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 1, characterized in that, The Trim structure after the leveling layer is formed is retested to obtain the residual height difference of the Trim structure. When the residual height difference is greater than a preset threshold, local respraying is performed.

8. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 1, characterized in that, Before spraying the leveling material onto the Trim structure, a primer is first sprayed onto the Trim structure. The primer continuously covers the inner transition area, the central depression area, and the outer edge area. The primer is then pre-baked to form a continuous base layer. Subsequently, the leveling material is sprayed onto the continuous base layer. The leveling material is mainly deposited in the central depression area and extends towards the inner transition area and the outer edge area, respectively, forming a leveling layer on the continuous base layer.

9. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 8, characterized in that, The preparation method of the primer material includes the following steps: Under nitrogen protection, 4,4'-diaminodiphenyl ether and diaminopropyl-terminated polydimethylsiloxane were added to N-methylpyrrolidone and stirred until dissolved. Then, pyromellitic dianhydride was added and the temperature was controlled. After the addition of materials is completed, stirring is continued for 8-12 hours under nitrogen protection; after the reaction is completed, some N-methylpyrrolidone is removed under reduced pressure, and the solid content and viscosity are adjusted to obtain polyamic acid solution. 3-Glycidyl etheroxypropyltrimethoxysilane was added to the polyamic acid adhesive solution, and after stirring, fumed silica was added. The mixture was then stirred and degassed under vacuum to obtain the primer material.

10. The wafer edge point spraying and leveling process based on Trim height measurement according to claim 8, characterized in that, The preparation method of the leveling material includes the following steps: Hollow silica particles were dried, cooled, and then added to anhydrous isopropanol. After stirring and ultrasonic treatment, a hollow silica dispersion was obtained. 3-Aminopropyltriethoxysilane was added to anhydrous isopropanol and stirred until homogeneous. Then it was added to the hollow silica dispersion and stirred. Hollow silica particles were separated, washed, and dried to obtain modified hollow silica particles. Under nitrogen protection, 4,4'-diaminodiphenyl ether was added to N-methylpyrrolidone and stirred until dissolved. Then, pyromellitic dianhydride was added in batches while controlling the temperature. After the addition was completed, stirring was continued for 8-12 hours under nitrogen protection. After the reaction was completed, some N-methylpyrrolidone was removed under reduced pressure, and the solid content and viscosity were adjusted to obtain polyamic acid solution. The modified hollow silica particles were dispersed in N-methylpyrrolidone to obtain a hollow silica dispersion. The hollow silica dispersion was added to the polyamic acid adhesive, followed by the addition of benzoxazine resin and fumed silica. After stirring and vacuum degassing, the leveling material was obtained.

Images