A laser-written magnetic thin-film packaging method for chip inductive elements

Abstract

This invention discloses a laser-direct-write magnetic thin-film encapsulation method for chip-based inductive elements, relating to the field of integrated circuit packaging technology. The method involves uniformly mixing magnetic nanoparticles with a curable adhesive to form a magnetic slurry, which is then uniformly coated onto a chip containing an inductive element. A laser is used to directionally irradiate the magnetic slurry above the inductive element, causing it to solidify and form a magnetic thin film that adheres tightly to the chip. Uncured magnetic slurry on the chip is then cleaned away, resulting in an inductive element encapsulated with the magnetic thin film. This method solidifies the magnetic film within a designated area of ​​the chip's inductive element, avoiding direct contact with the element's surface. This prevents chip interface damage and device failure, as well as issues such as secondary diffusion failure of active devices due to excessive temperature. It is fully compatible with standard semiconductor processes, facilitating commercial applications. The encapsulation process is simple, efficient, and flexible.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit packaging technology, and in particular to a laser-direct-write magnetic thin-film packaging method for chip inductive components. Background Technology

[0002] Inductive components such as on-chip inductors and transformers (i.e., "on-chip inductive components") are important parts of radio frequency (RF) integrated circuits and are widely used in fields such as radio frequency front-end chips (RFICs). Compared with other on-chip components, on-chip inductive components suffer from large area and low performance, which seriously hinders the miniaturization and high-frequency development of RF integrated circuits. Researchers have attempted to improve device performance by modifying the structure of on-chip components, but these methods cannot simultaneously achieve miniaturization and high performance of on-chip inductive components.

[0003] To enhance the magnetic storage capacity and reduce magnetic leakage of inductive components, integrating magnetic materials into them is an effective method to improve performance and reduce area. However, in existing technologies, integrating magnetic ferrites into chip inductive components using magnetron sputtering requires high-temperature post-processing exceeding 600°C for crystallization. This negatively impacts the already fabricated active devices on the chip. To avoid the high temperatures during ferrite integration, researchers have used low-temperature processes such as screen printing and stencil methods to integrate magnetic ferrites into on-chip inductive components. However, due to differences in process platforms and packaging technologies, these methods are incompatible with standard semiconductor processes, preventing their use and hindering the commercial application of chip magnetic film inductive components fabricated using these methods.

[0004] Therefore, developing a low-temperature integration process for magnetic materials that is compatible with standard semiconductor processes is key to realizing the commercial application of chip-based inductive components with integrated magnetic films. Summary of the Invention

[0005] To meet the requirements of chip miniaturization and high performance, and to realize the application of magnetic materials in chip inductive components, it is necessary to find a low-temperature process compatible with standard IC processes for the integration of magnetic materials in chip inductive components. This invention provides a laser-direct-write magnetic thin-film packaging method for chip inductive components. This method not only enables low-temperature integration and packaging of magnetic materials in chip inductive components but also has the characteristic of compatibility with standard semiconductor processes. Specifically, it is achieved through the following techniques.

[0006] A laser-written magnetic thin-film encapsulation method for chip inductive components includes the following steps:

[0007] Magnetic nanoparticles are mixed evenly with a curing adhesive to form a magnetic slurry, which is then uniformly coated onto a chip containing inductive elements.

[0008] The magnetic paste above the chip's inductive element is irradiated with a laser to solidify it into a magnetic thin film, which then adheres to the chip.

[0009] The uncured magnetic paste on the chip is removed by cleaning, resulting in an inductive element encapsulated by a magnetic thin film on the chip.

[0010] Furthermore, the laser spot is aligned with the alignment mark on the chip to be processed, and the laser spot is focused on the surface of the chip to be processed; the laser spot is aligned with the area of ​​the magnetic thin film to be packaged corresponding to the inductive element on the chip to be processed.

[0011] Furthermore, the laser curing magnetic film encapsulation method for chip inductive elements provided by the present invention adopts a laser selection method, aligning the laser spot with the inductive element area of ​​the magnetic film to be encapsulated on the chip to be processed (for example, by adjusting a multi-axis moving platform), so that the curable adhesive in the magnetic slurry in the selected area undergoes a cross-linking reaction and solidifies under the action of the laser.

[0012] Furthermore, the magnetic nanoparticles have a size of 5 nm to 500 nm.

[0013] Furthermore, the mass ratio of the magnetic nanoparticles to the curable adhesive does not exceed 3:4.

[0014] Furthermore, the mass ratio of the magnetic nanoparticles to the curable adhesive is 3:4.

[0015] Furthermore, the curable adhesive is a polymer that has been cured by laser irradiation.

[0016] Furthermore, the cured adhesive is epoxy resin or phenolic resin.

[0017] Furthermore, the laser is an infrared laser or an ultraviolet laser.

[0018] Furthermore, the cleaning method is ultrasonic cleaning or plasma cleaning.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] 1. The magnetic thin film encapsulation method for chip inductive elements provided by the present invention completes the entire curing and encapsulation process by laser direct writing, without directly contacting the surface of inductive elements and other devices, which can effectively avoid chip interface damage and device failure caused by direct contact with devices in processes such as screen printing.

[0021] 2. The magnetic thin film packaging method for chip inductive components provided by the present invention does not require a high temperature during the packaging process, meeting the requirement that the semiconductor back-end process temperature should not exceed 400°C. It is a relatively low temperature packaging method, which can effectively avoid problems such as secondary diffusion failure of charge carriers in chip active devices caused by excessively high post-processing temperatures.

[0022] 3. The magnetic thin film packaging method for chip inductive elements provided by the present invention is fully compatible with standard semiconductor processes, which is conducive to the commercial application of chip magnetic film inductive elements.

[0023] 4. This invention utilizes laser to rapidly solidify magnetic paste in a designated area, enabling on-chip magnetic thin-film encapsulation of inductive components through a single-step laser direct-write process. This encapsulation method is highly efficient and fast. Compared to integration methods such as magnetron sputtering, this invention significantly improves encapsulation efficiency and reduces encapsulation process time.

[0024] 5. The laser direct-writing magnetic thin film encapsulation method provided by this invention can precisely control the laser beam through a computer system-controlled galvanometer and multi-axis moving platform to achieve patterned encapsulation of a specified area. Compared with traditional magnetic thin film preparation methods such as screen printing, the method provided by this invention is simpler, easier to control, and more flexible in application. Attached Figure Description

[0025] Figure 1 A process flow diagram of the laser direct-write magnetic thin film packaging method for chip inductive elements provided by the present invention.

[0026] Figure 2 This is an infrared thermograph of the laser thermosetting encapsulation magnetic film process in Example 1.

[0027] Figure 3 This is a scanning electron microscope image of the magnetic thin film encapsulated in Example 1.

[0028] Figure 4 This is an optical image of the on-chip magnetic film inductor prepared in Example 1.

[0029] Figure 5 This is a performance comparison chart of the on-chip magnetic film inductor prepared in Example 1.

[0030] Figure 6 (a), (b), and (c) are the hysteresis loops of the magnetic thin films encapsulated under different laser parameters in Examples 2, 3, and 4, respectively. Figure 6 (d) represents the hysteresis loop of the magnetic thin film encapsulated with magnetic pastes configured with different mass ratios in Example 5. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The laser-written magnetic thin-film packaging method for chip inductive elements provided in some embodiments of the present invention, such as... Figure 1 As shown, it includes the following steps:

[0033] Magnetic nanoparticles are mixed evenly with a curing adhesive to form a magnetic slurry, which is then uniformly coated onto a chip containing inductive elements.

[0034] The magnetic paste above the inductive element on the chip is irradiated with a laser to solidify it into a magnetic film, which is then bonded to the chip.

[0035] The uncured magnetic paste on the chip is removed by cleaning, and the inductive element encapsulated by a magnetic thin film is obtained on the chip.

[0036] In the above method, the magnetic paste is cured and encapsulated by laser directional irradiation. Specifically, the laser spot is aligned with the alignment mark of the chip to be processed, the multi-axis moving platform is adjusted to focus the laser spot on the surface of the chip to be processed, and the laser spot is moved to the area of ​​the magnetic thin film to be encapsulated corresponding to the inductive element on the chip to be processed by the galvanometer system.

[0037] Furthermore, the laser curing magnetic film encapsulation method for chip inductive elements provided by the present invention adopts a laser selection method, aligning the laser spot with the inductive element area of ​​the magnetic film to be encapsulated on the chip to be processed (for example, by adjusting a multi-axis moving platform), so that the curable adhesive in the magnetic slurry in the selected area undergoes a cross-linking reaction and solidifies under the action of the laser.

[0038] Optionally, the magnetic nanoparticles have a size of 5 nm to 500 nm.

[0039] Optionally, the mass ratio of the magnetic nanoparticles to the curable adhesive does not exceed 3:4.

[0040] Specifically, the mass ratio of the magnetic nanoparticles to the curable adhesive is 3:4.

[0041] Optionally, the curable adhesive is a polymer that has been cured by laser irradiation.

[0042] Further optionally, the cured adhesive is an epoxy resin or a phenolic resin.

[0043] Optionally, the laser is an infrared laser or an ultraviolet laser.

[0044] Optionally, the cleaning method is ultrasonic cleaning or plasma cleaning.

[0045] Example 1

[0046] The laser-written magnetic thin-film packaging method for chip inductive elements provided in this embodiment includes the following steps:

[0047] (1) The silicon wafer with planar inductance was cleaned by ultrasonic cleaning in acetone, ethanol and deionized water for 15 min in sequence, and then dried. In this example, the silicon wafer thickness was 500 μm and the silicon dioxide layer thickness was 300 nm.

[0048] (2) The magnetic powder of ferric oxide with a particle size of 80 nm (specification model 80 nm, purchased from Zhihan New Materials Suzhou Co., Ltd.) and the curing epoxy resin adhesive were mixed evenly at a mass ratio of 3:4. The nano magnetic particles were uniformly dispersed in the slurry by mechanical stirring for 20 min and vacuum degassing for 15 min to obtain magnetic slurry.

[0049] The curing adhesive used in this embodiment is a single-component epoxy resin low-temperature thermosetting adhesive, purchased from Shenzhen Xuzhuo New Material Technology Co., Ltd., product model 6201.

[0050] (3) The magnetic paste is uniformly spin-coated onto the silicon wafer on which the inductor device is prepared by the above-mentioned spin coating method. The spin coating speed is 4000 r / min and the spin coating time is 40 s.

[0051] (4) Place and fix the silicon wafer coated with magnetic paste on the multi-axis moving platform; adjust the multi-axis moving platform system to align the laser beam spot with the alignment mark on the silicon wafer and focus the laser beam spot on the workpiece surface; adjust the galvanometer system to move the laser beam spot to the area of ​​the magnetic thin film to be packaged on the wafer inductor.

[0052] (5) Use an infrared fiber laser with a wavelength of 1064 nm to irradiate the magnetic paste on the inductor along a pre-set scanning path to solidify it into a magnetic thin film and bond it tightly to the wafer.

[0053] The main laser processing parameters are as follows: continuous mode operation, Gaussian focal spot beam shape, 0.2 W laser power, 280 mm / s scanning speed, 1250 scans, 25 μm scanning interval, and 75% spot overlap rate.

[0054] Under these laser process parameters, the infrared thermogram of the laser-cured and encapsulated magnetic thin film is as follows: Figure 2As shown, the highest temperature is 123℃. The cured and encapsulated magnetic film product is as follows... Figure 3 As shown.

[0055] (6) Remove the uncured magnetic paste on the silicon wafer by ultrasonic cleaning with anhydrous ethanol.

[0056] The ultrasonic cleaning power is 240 W, and the process time is 2 min.

[0057] (7) After the silicon wafer sample dries naturally, the on-chip inductor with completed magnetic thin film encapsulation is obtained, such as Figure 4 As shown.

[0058] The performance of the planar inductor encapsulated with a magnetite thin film was tested. The test results are as follows: Figure 5 As shown, compared to planar inductors of the same type, the on-chip magnetic film inductor packaged using the method of this embodiment exhibits a 20.2% improvement in inductance (L) and a 7% improvement in quality factor (Q) at 1 GHz. In long-term testing, the magnetic film packaged on the on-chip inductive element using laser direct writing exhibits good reliability and consistency.

[0059] Example 2

[0060] The laser-direct-write magnetic thin-film packaging method for chip inductive elements provided in this embodiment is basically the same as that in Embodiment 1, except that: the laser used in this embodiment is a 1064 nm wavelength infrared laser, and the laser operating parameters are: laser power 0.4 W, scanning speed 280 mm / s, number of scans 1250, scanning spacing 25 μm, and spot overlap rate 75%. Figure 6 As shown in (a), the laser power of group A is 0.4 W, and the laser power of group B is 0.2 W. It can be seen that the change in laser power does not have a significant impact on the hysteresis characteristics of the packaged magnetic film.

[0061] Example 3

[0062] The laser-direct-write magnetic thin-film packaging method for chip inductive elements provided in this embodiment is basically the same as that in Embodiment 1, except that: the laser used in this embodiment is a 1064 nm wavelength infrared laser, and the laser operating parameters are: laser power 0.2 W, scanning speed 250 mm / s, number of scans 1250, scanning spacing 25 μm, and spot overlap rate 75%. Figure 6 As shown in (b), the scanning speed for group A is 280 mm / s, and the scanning speed for group B is 250 mm / s. It can be seen that the change in scanning speed does not have a significant impact on the hysteresis characteristics of the packaged magnetic film.

[0063] Example 4

[0064] The laser-direct-write magnetic thin-film packaging method for chip inductive elements provided in this embodiment is basically the same as that in Embodiment 1, except that: the laser used in this embodiment is a 1064 nm wavelength infrared laser, and the laser operating parameters are: laser power 0.2 W, scanning speed 280 mm / s, 1500 scans, scanning spacing 25 μm, and spot overlap rate 75%. Figure 6 As shown in (c), the number of scans for group A was 1250, and the number of scans for group B was 1500. It can be seen that the change in the number of scans did not significantly affect the hysteresis characteristics of the packaged magnetic film.

[0065] Example 5

[0066] The laser direct-write magnetic thin film encapsulation method for chip inductive elements provided in this embodiment has basically the same steps as in Embodiment 1, except that: in this embodiment, the mass ratio of magnetic nanoparticles to curable adhesive is 1:2 or 1:4.

[0067] like Figure 6 As shown in (d), the mass ratio of magnetic nanoparticles to curable adhesive is 1:4 for group A, 1:2 for group B, and 3:4 for group C. It can be seen that the hysteresis characteristics of the encapsulated magnetic film are related to the content of magnetic particles in the film; the lower the content of magnetic particles, the lower the saturation magnetization of the magnetic film. The higher the magnetic content of the magnetic film encapsulated on inductive components, the more significant the improvement in device performance.

[0068] Example 6

[0069] The laser direct-write magnetic thin film encapsulation method for chip inductive elements provided in this embodiment has basically the same steps as that in Embodiment 1. The difference is that the curing adhesive used in this embodiment is a single-component phenolic resin thermosetting adhesive, which is purchased from Gongyi Borun Refractory Materials Co., Ltd., and the product model is 2130.

[0070] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A laser-written magnetic thin-film encapsulation method for chip inductive elements, characterized in that, Includes the following steps: Magnetic nanoparticles are mixed evenly with a curing adhesive to form a magnetic slurry, which is then uniformly coated onto a chip containing inductive elements. The magnetic paste above the chip's inductive element is irradiated with an infrared laser to solidify it into a magnetic film that adheres to the chip. Cleaning removes the uncured magnetic paste from the chip, resulting in an inductive element encapsulated by a magnetic thin film on the chip; The method of laser directional irradiation is as follows: align the laser spot with the alignment mark of the chip to be processed, and focus the laser spot on the surface of the chip to be processed; align the laser spot with the area of ​​the magnetic thin film to be packaged corresponding to the inductive element on the chip to be processed.

2. The laser-written magnetic thin-film packaging method for chip inductive elements according to claim 1, characterized in that, The magnetic nanoparticles have a size of 5 nm to 500 nm.

3. The laser-direct-write magnetic thin-film packaging method for chip inductive elements according to claim 1, characterized in that, The mass ratio of the magnetic nanoparticles to the curable adhesive does not exceed 3:

4.

4. The laser-direct-write magnetic thin-film packaging method for chip inductive elements according to claim 1, characterized in that, The curing adhesive is a high molecular polymer that has been cured by laser irradiation.

5. The laser-direct-write magnetic thin-film packaging method for chip inductive elements according to claim 4, characterized in that, The cured adhesive is epoxy resin or phenolic resin.

6. The laser-direct-write magnetic thin-film packaging method for chip inductive elements according to claim 1, characterized in that, The cleaning method is ultrasonic cleaning or plasma cleaning.

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