Wafer packaging method and wafer packaging structure of resonator

Abstract

The invention provides a wafer packaging method and a wafer packaging structure of a resonator. The wafer packaging method of the resonator comprises the following steps: providing a device wafer; the front surface of the device wafer is provided with a resonator area, and the resonator area is provided with a resonator and a supporting layer; providing a top cover wafer, and partially removing an area, corresponding to the resonator area, of the top cover wafer so as to form a bulge in the resonator area; the top cover wafer is arranged on a device wafer, and the top cover wafer is connected with the protrusions through the supporting layer; and processing one side, far away from the device wafer, of the top cover wafer to form packaging of the resonator. The problems that an existing top cover wafer packaging mode is low in production efficiency, extra purging is needed, a cutting knife is prone to breakage, and the edge of a silicon cover is prone to serious breakage are solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and more specifically, to a wafer packaging method and wafer packaging structure for a resonator. Background Technology

[0002] Bulk acoustic wave (BAW) resonators, as important microelectromechanical devices, must operate in a vacuum or controlled atmosphere environment to ensure stable performance. Currently, temperature-compensated bulk acoustic wave (TC-BAW) devices require packaging before shipment, typically using a silicon cap covering the resonator, exposing only the pad area for electrical connections.

[0003] Existing packaging solutions typically employ a bonding method between the top cover wafer and the device wafer: the device region of the device wafer is bonded to the top cover wafer using a dry film, while other regions remain suspended. The top cover wafer is then ground, and a single silicon cap structure is formed through two horizontal and two vertical cuts. However, this approach has significant drawbacks: the dicing process requires hundreds of cuts with both horizontal and vertical blades, resulting in a dicing time of 4 to 5 hours per wafer and extremely low production efficiency; each cut requires a process engineer to be on standby, hindering continuous mass production and resulting in low industrialization levels; the cut silicon strips continuously fall off during the dicing process, necessitating an additional blowing and washing process, which can easily lead to blade breakage, and the edges of the diced silicon cap are prone to severe chipping, affecting packaging quality and device reliability. Summary of the Invention

[0004] The problem solved by this invention is that existing top-cover wafer packaging methods have low production efficiency, require additional cleaning, are prone to dicing blade breakage, and are prone to severe chipping at the edge of the silicon cover.

[0005] To address the above problems, the present invention provides a wafer packaging method for a resonator, the wafer packaging method for the resonator comprising: A device wafer is provided; the front side of the device wafer has a resonator region, and the resonator region is provided with a resonator and a support layer; A top cover wafer is provided, and a portion of the area of ​​the top cover wafer corresponding to the area outside the resonator region is removed to form a protrusion in the resonator region; The top cover wafer is placed on the device wafer and bonded to the protrusion through the support layer; The side of the top cover wafer furthest from the device wafer is processed to form a package for the resonator.

[0006] Since the other side of the top cover wafer is removed entirely, the openings around the bumps are opened while the bumps are retained. This method of removing the bumps from the front replaces the existing method of cutting the sides of the bumps multiple times, which greatly shortens the process time. Since manual cutting is not required, the problems of tool breakage and chipping at the edge of the top cover wafer caused by the cutting blade are avoided, which improves mass production capability and reduces costs.

[0007] Furthermore, the thickness of the top cover wafer is greater than that of the protrusion; the step of partially removing the area of ​​the top cover wafer corresponding to the area outside the resonator region to form the protrusion in the resonator region specifically includes: etching the area outside the resonator region on the surface of the top cover wafer according to the target thickness of the protrusion to obtain the protrusion and the layer to be removed connected to the protrusion.

[0008] Furthermore, the process of processing the side of the top cover wafer away from the device wafer to form a package for the resonator specifically includes: grinding the side of the top cover wafer away from the device wafer to a depth reaching the etched position to retain the protrusion.

[0009] Furthermore, the angle α between the side of the protrusion and the layer to be removed is ≥90°.

[0010] Furthermore, the step of placing the top cover wafer on the device wafer specifically includes: covering the resonator with the protrusion and bonding it to the support layer.

[0011] Because the side of the top cover wafer bonded to the support layer is not planar, when the included angle α < 90°, an embedded sharp corner will be formed. During pressure bonding, there will be obvious stress concentration at the root of the sharp corner, which will cause damage. Therefore, α ≥ 90° can effectively improve the stability of the top cover wafer and avoid damage to the device caused by the breakage of the top cover wafer.

[0012] Furthermore, the lateral distance d between the edge of the protrusion and the support layer is ≥5μm.

[0013] Because a lateral distance is reserved between the protruding edge and the support layer, i.e. a process window is reserved, the chip performance is avoided from being affected by deviations in the process parameters of the material itself.

[0014] Furthermore, the thickness d of the support layer is between 50 μm and 150 μm.

[0015] Furthermore, the support layer is a dry film.

[0016] The present invention also provides a wafer packaging structure for a resonator, used to implement the wafer packaging method for a resonator as provided in any of the above technical solutions. The wafer packaging structure for the resonator includes: a device wafer and a top cover wafer; the front side of the device wafer has a resonator region, and the resonator region is provided with a resonator and a support layer; the top cover wafer is used to form the protrusion, the protrusion corresponds to the resonator region, and is supported by the support layer.

[0017] Furthermore, the resonator is a bulk acoustic resonator.

[0018] In summary, the above-mentioned technical solutions of this application can have one or more of the following advantages or beneficial effects: the target protrusion can be quickly formed on the top cover wafer by etching, and the side of the top cover away from the protrusion can be directly ground away in one layer. While retaining the protrusion, the opening on the periphery of the protrusion is also opened, which greatly shortens the process time, avoids the problem of tool breakage caused by the dicing tool and the chipping of the top cover wafer edge, improves mass production capability and reduces costs; the bonding process between the top cover wafer and the support layer requires a pressure process, and the included angle α≥90° can avoid stress concentration at the included angle, thereby effectively improving the stability of the protrusion. Attached Figure Description

[0019] Figure 1 A flowchart illustrating a wafer packaging method for a resonator provided by the invention; Figure 2 This is a schematic diagram of the wafer packaging structure in step S2; Figure 3 This is a schematic diagram of the wafer packaging structure in step S3; Figure 4 This is a schematic diagram of the wafer packaging structure in step S4.

[0020] Explanation of reference numerals in the attached figures: 100 - Wafer package structure; 110 - Device wafer; 111 - Resonator; 112 - Support layer; 120 - Top cover wafer; 121 - Bump. Detailed Implementation

[0021] The purpose of this invention is to provide a wafer packaging method and wafer packaging structure for resonators, which can achieve efficient processing, avoid the problems of dicing blade breakage and chipping at the edge of the top cover wafer, and achieve a stable raised effect.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] See Figures 1-4 The present invention provides a wafer packaging method for a resonator 111, the wafer packaging method for the resonator 111 includes: Step S1: Provide device wafer 110; the front side of device wafer 110 has a resonator 111 area, and the resonator 111 area is provided with a resonator 111 and a support layer 112. Step S2: Provide a top cover wafer 120, and partially remove the area of ​​the top cover wafer 120 corresponding to the area outside the resonator 111 region to form a bump 121 in the resonator 111 region; Step S3: Place the top cover wafer 120 on the device wafer 110 and bond it to the bump 121 through the support layer 112; Step S4: Process the side of the top cover wafer 120 away from the device wafer 110 to form a package for the resonator 111.

[0024] Since the other side of the top cover wafer 120 is removed entirely, while retaining the protrusion 121, the opening around the protrusion 121 is also opened. The front-side removal method replaces the existing solution of cutting the side of the protrusion 121 multiple times, which greatly shortens the process time. Since manual cutting is not required, the problems of tool breakage and edge chipping of the top cover wafer 120 caused by the cutting tool are avoided, which improves mass production capability and reduces costs.

[0025] In one specific embodiment, the thickness of the top cover wafer 120 is greater than that of the bump 121; partial removal of the area of ​​the top cover wafer 120 corresponding to the area outside the resonator 111 region to form the bump 121 in the resonator 111 region specifically includes: etching the area outside the resonator 111 region on the surface of the top cover wafer 120 according to the target thickness of the bump 121 to obtain the bump 121 and the layer to be removed connected to the bump 121.

[0026] It should be noted that both the top cover wafer 120 and the device wafer 110 use a silicon substrate.

[0027] Preferably, the portion outside the protrusion 121 is matched with the thickness of the target protrusion 121 by controlling the deep silicon etching depth, so as to ensure the size consistency and process controllability of the protrusion 121 and improve the packaging yield.

[0028] In one specific embodiment, the side of the top cover wafer 120 away from the device wafer 110 is processed to form a package for the resonator 111. Specifically, this includes grinding the side of the top cover wafer 120 away from the device wafer 110 to a depth that reaches the etched position to retain the protrusion 121.

[0029] Among them, the grinding method is used to remove excess material in one go. The process is simple and efficient, and avoids the physical impact and silicon strip falling off during the cutting process.

[0030] In one specific embodiment, a layer of silicon dioxide is grown or deposited on the surface of the top cover wafer 120 via thermal oxidation or chemical vapor deposition as a hard mask for subsequent deep reactive ion etching (RIE) processes. Silicon dioxide exhibits a high etch selectivity to silicon. Next, photoresist is spin-coated onto the oxide layer, and exposure is performed using a photomask. The design pattern of this photomask defines the area of ​​the bump 121 to be retained and the cavities to be removed. After development, the photoresist layer forms a pattern opposite to that of the photomask, exposing the oxide layer in the areas to be etched. A reactive ion etching process is then used to remove the silicon dioxide layer in the exposed areas, transferring the pattern onto the oxide layer to form a hard mask window. Finally, the photoresist residue and the mask layer are removed to obtain the bump 121.

[0031] In one specific embodiment, the angle α between the side of the protrusion 121 and the layer to be removed is ≥90°.

[0032] In one specific embodiment, the top cover wafer 120 is disposed on the device wafer 110, specifically including: covering the resonator 111 with the protrusion 121 and bonding it to the support layer 112.

[0033] Reliable sealing between the protrusion 121 and the resonator 111 region is achieved through bonding with the support layer 112, providing mechanical protection and environmental isolation. Due to the non-planar structure of one side of the top cover wafer 120 bonded to the support layer 112, an embedded sharp corner will be formed when the included angle α of the protrusion 121 is less than 90°. During pressure bonding, there will be significant stress concentration at the root of the sharp corner, leading to damage. Controlling the included angle between the side of the protrusion 121 and the layer to be removed to 90° or greater can effectively improve the strength of the top cover wafer 120 and prevent the top cover wafer 120 from breaking and damaging the device.

[0034] In one specific embodiment, the support layer 112 is a dry film. The dry film is a solid film formed by applying a polymer material coated on a substrate under high temperature and pressure, such as a resin material. Using a dry film as the support layer 112 offers good patterning capabilities and bonding compatibility, making it suitable for wafer-level packaging processes.

[0035] Preferably, the bumps 121 of the top cover wafer 120 and the device wafer 110 are precisely mechanically aligned in a bonding machine to ensure that each bump 121 accurately covers its corresponding resonator 111 region, and that the edges of the bumps 121 fall within the area of ​​the support layer 112. After alignment, the bonding machine applies vertical pressure to the wafer stack while simultaneously heating the entire stack to a bonding temperature higher than the glass transition temperature of the dry film. Under this temperature and pressure, the dry film softens, flows, and undergoes plastic deformation, fully wetting the microscopic irregularities on the lower surface of the bumps 121 and filling the gaps between them and the surface of the device wafer 110, forming a tight contact. At the tight contact interface, strong van der Waals forces are generated between the polymer molecules in the dry film and the silicon oxide on the surface of the silicon top cover wafer 120, thereby achieving a high-strength, high-hermetic-tight bond. After bonding is completed, the stack is cooled to room temperature while maintaining or slowly reducing the pressure. The dry film cures to form a robust, sealed bonding interface, permanently fixing the protrusion 121 to the device wafer 110.

[0036] In one specific embodiment, the lateral distance d between the edge of the protrusion 121 and the support layer 112 is ≥ 5 μm.

[0037] Because a lateral distance is reserved between the edge of the protrusion 121 and the support layer 112, i.e. a process window is reserved, the chip performance is avoided due to deviation of the process parameters of the material itself, and the sealing failure caused by adhesive overflow or alignment error during the bonding process is avoided.

[0038] In one specific embodiment, the thickness d of the support layer 112 is between 50 μm and 150 μm. For example, the thickness d of the support layer 112 is 100 μm to improve the strength of the balance support layer 112 and ensure the stability of the encapsulation.

[0039] The present invention also provides a wafer packaging structure 100 for a resonator 111, used to implement the wafer packaging method for the resonator 111 provided by any of the above technical solutions. The wafer packaging structure 100 for the resonator 111 includes: a device wafer 110 and a top cover wafer 120; the front side of the device wafer 110 has a resonator 111 region, and the resonator 111 region is provided with a resonator 111 and a support layer 112; the top cover wafer 120 is used to form a protrusion 121, the protrusion 121 corresponds to the resonator 111 region, and is supported by the support layer 112.

[0040] In one specific embodiment, the resonator 111 is a bulk acoustic resonator 111.

[0041] It should be noted that the packaging structure obtained by the wafer packaging method of the resonator 111 described above achieves a highly reliable seal, avoids chipping and contamination introduced by cutting, and is suitable for mass production of bulk acoustic wave resonator 111.

[0042] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A wafer packaging method for a resonator, characterized in that, The wafer packaging method for the resonator includes: A device wafer is provided; the front side of the device wafer has a resonator region, and the resonator region is provided with a resonator and a support layer; A top cover wafer is provided, and a portion of the area of ​​the top cover wafer corresponding to the area outside the resonator region is removed to form a protrusion in the resonator region; The top cover wafer is placed on the device wafer and bonded to the protrusion through the support layer; The side of the top cover wafer furthest from the device wafer is processed to form a package for the resonator.

2. The wafer packaging method for the resonator according to claim 1, characterized in that, The thickness of the top cover wafer is greater than that of the protrusion; The partial removal of the area of ​​the top cover wafer corresponding to the resonator region to form a protrusion in the resonator region specifically includes: Based on the target thickness of the protrusion, the area outside the resonator region is etched on the surface of the top cover wafer to obtain the protrusion and the layer to be removed connected to the protrusion.

3. The wafer packaging method for the resonator according to claim 2, characterized in that, The process of processing the side of the top cover wafer away from the device wafer to form a package for the resonator specifically includes: The side of the top cover wafer furthest from the device wafer is ground down to the etched position to preserve the protrusion.

4. The wafer packaging method for the resonator according to claim 2, characterized in that, The angle α between the side of the protrusion and the layer to be removed is ≥90°.

5. The wafer packaging method for the resonator according to claim 1, characterized in that, The step of setting the top cover wafer on the device wafer specifically includes: The protrusion covers the resonator and is bonded to the support layer.

6. The wafer packaging method for the resonator according to claim 1, characterized in that, The lateral distance d between the edge of the protrusion and the support layer is ≥5μm.

7. The wafer packaging method for the resonator according to claim 1, characterized in that, The thickness d of the support layer ranges from 50 μm to 150 μm.

8. The wafer packaging method for the resonator according to claim 1, characterized in that, The support layer is a dry film.

9. A wafer packaging structure for a resonator, used to implement the wafer packaging method for the resonator as described in any one of claims 1-8, characterized in that, The wafer package structure of the resonator includes: the device wafer and the top cover wafer; The device wafer has a resonator region on the front side, and the resonator region is provided with a resonator and a support layer; The top cover wafer is used to form the protrusion, which corresponds to the resonator region and is supported by the support layer.

10. The wafer packaging structure of the resonator according to claim 9, characterized in that, The resonator is a bulk acoustic resonator.

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