Laser direct writing magnetic film packaging method of chip inductive element

Abstract

The invention discloses a laser direct writing magnetic thin film packaging method for a chip inductive element, and relates to the technical field of integrated circuit packaging. The method comprises the following steps: uniformly mixing magnetic nanoparticles with a curing adhesive to prepare magnetic slurry, and uniformly coating the magnetic slurry on a chip with an inductive element; the magnetic slurry above the inductive element of the chip is directionally irradiated by laser, so that the magnetic slurry is solidified to form a magnetic thin film which is tightly adhered to the chip; and cleaning and removing the uncured magnetic slurry on the chip to obtain the inductive element packaged by the magnetic thin film on the chip. By adopting the method, the magnetic film is solidified and packaged in the specified area of the inductive element of the chip, and the surface of the inductive element is not directly contacted, so that the problems of chip interface damage, device failure, secondary diffusion failure of carriers of an active device of the chip caused by over-high temperature and the like can be avoided; the method can be completely compatible with a standard semiconductor process, and commercial application is facilitated; and the packaging process is simple, efficient and flexible.

Description

Technical Field

[0001] The invention relates to the technical field of integrated circuit packaging, and in particular to a laser direct writing magnetic thin film packaging method for a chip inductive element. Background Art

[0002] On-chip inductors, transformers and other inductive components (i.e., "on-chip inductive components") are important components of radio frequency 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 have the problems of large area and low performance, which seriously hinders the development of radio frequency integrated circuits towards miniaturization and high frequency. Relevant researchers have tried to improve device performance by improving the structure of on-chip components, but these methods cannot achieve both miniaturization and high performance of on-chip inductive components.

[0003] In order to enhance the magnetic storage capacity of the inductive element and reduce the magnetic leakage phenomenon, integrating magnetic materials into the inductive element is an effective method to promote the performance improvement and area reduction of the inductive element. However, in the prior art, when the magnetic ferrite is integrated into the chip inductive element by the magnetron sputtering process, a high-temperature post-treatment process of more than 600°C is required for crystallization. This will have a negative impact on the active devices that have been prepared on the chip. In order to avoid high temperatures during the ferrite integration process, researchers used low-temperature processes such as screen printing and stencil methods to integrate magnetic ferrites into on-chip inductive elements. However, due to technical differences in process platforms and packaging, these methods are incompatible with standard semiconductor processes, resulting in these methods being unable to be used in standard semiconductor processes, and the chip magnetic film inductive elements prepared by these methods cannot be commercially applied.

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

[0005] In order to meet the requirements of miniaturization and high performance of chips and realize the application of magnetic materials in chip inductive elements, it is necessary to find a low-temperature process compatible with standard IC process for the integration of magnetic materials in chip inductive elements. The present invention provides a laser direct writing magnetic thin film packaging method for chip inductive elements, which can not only realize the low-temperature integrated packaging of magnetic materials in chip inductive elements, but also has the characteristics of compatibility with standard semiconductor processes. It is specifically achieved through the following technologies.

[0006] A laser direct writing magnetic thin film packaging method for a chip inductive element comprises the following steps:

[0007] The magnetic nanoparticles are mixed evenly with a curable adhesive to form a magnetic slurry, and the magnetic slurry is evenly coated on the chip with the inductive element;

[0008] Using laser to irradiate the magnetic paste above the chip inductive element in a direction so that the magnetic paste is solidified to form a magnetic film and adhered to the chip;

[0009] The uncured magnetic slurry on the chip is cleaned and removed, and a sensitive element encapsulated by a magnetic film is obtained on the chip.

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

[0011] Furthermore, the laser-cured magnetic film packaging method for chip inductive elements provided by the present invention adopts a laser selection method to align the laser spot with the inductive element area of ​​the magnetic film to be packaged on the chip to be processed (for example, by adjusting a multi-axis moving platform, etc.), so that the curing 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 size of the magnetic nanoparticles is 5 nm-500 nm.

[0013] Furthermore, the mass ratio of the magnetic nanoparticles to the curing adhesive is no more than 3:4.

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

[0015] Furthermore, the curable adhesive is a high molecular polymer cured by laser irradiation.

[0016] Furthermore, the curing 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 present invention is beneficial in that:

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

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

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

[0023] 4. The present invention uses laser to quickly solidify the magnetic slurry in the specified area, and can realize the magnetic thin film packaging of the on-chip inductive element through a single-step laser direct writing process. The packaging method is efficient and fast. Compared with integration methods such as magnetron sputtering, the present invention can greatly improve the packaging efficiency and reduce the packaging process time.

[0024] 5. The laser direct writing magnetic thin film packaging method provided by the present invention can accurately control the laser beam by controlling the galvanometer and the multi-axis mobile platform through the computer system to achieve patterned packaging of the specified area. Compared with traditional magnetic thin film preparation methods such as screen printing, the method provided by the present invention is simpler, easier to control, and more flexible in application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart of the laser direct writing magnetic thin film packaging method for the chip inductive element provided by the present invention.

[0026] Figure 2 This is an infrared thermal temperature diagram during the laser thermal curing packaging magnetic film process in Example 1.

[0027] Figure 3 This is a scanning electron microscope image of the magnetic 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 films packaged in Examples 2, 3 and 4 under different laser parameters, respectively. Figure 6 (d) is the hysteresis loop of the magnetic film encapsulated by the magnetic slurry with different mass ratios in this embodiment 5. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Some embodiments of the present invention provide a laser direct writing magnetic thin film packaging method for a chip inductive element, such as Figure 1 As shown, the following steps are included:

[0033] The magnetic nanoparticles and the curing adhesive are evenly mixed to form a magnetic slurry, which is evenly coated on the chip prepared with the inductive element.

[0034] Laser is used to irradiate the magnetic paste above the inductive element on the chip in a direction manner, so that the magnetic paste is solidified to form a magnetic film and adhered to the chip.

[0035] The uncured magnetic slurry on the chip is cleaned and removed, so that the inductive element encapsulated by the magnetic film is obtained on the chip.

[0036] In the above method, laser directionally irradiates the magnetic slurry for curing and packaging, specifically, aligning the laser spot with the alignment mark of the chip to be processed, adjusting the multi-axis moving platform, and focusing the laser spot on the surface of the chip to be processed; through the galvanometer system, the laser spot is moved to the area of ​​the magnetic film to be packaged corresponding to the inductive element on the chip to be processed.

[0037] Furthermore, the laser-cured magnetic film packaging method for chip inductive elements provided by the present invention adopts a laser selection method to align the laser spot with the inductive element area of ​​the magnetic film to be packaged on the chip to be processed (for example, by adjusting a multi-axis moving platform, etc.), so that the curing 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 size of the magnetic nanoparticles is 5 nm-500 nm.

[0039] Optionally, the mass ratio of the magnetic nanoparticles to the curing adhesive is no more than 3:4.

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

[0041] Optionally, the curable adhesive is a high molecular polymer cured by laser irradiation.

[0042] Further optionally, the curing adhesive is epoxy resin or 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 direct writing magnetic thin film packaging method of the chip inductive element provided in this embodiment includes the following steps:

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

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

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

[0050] (3) The magnetic slurry is evenly spin-coated on the silicon wafer with the inductor device by a coating method, wherein the spin coating speed is 4000 r / min and the spin coating time is 40 s.

[0051] (4) Placing and fixing the silicon wafer coated with magnetic slurry on a multi-axis moving platform; adjusting the multi-axis moving platform system to align the laser beam spot with the alignment mark on the silicon wafer, and focusing the laser beam spot on the workpiece surface; adjusting the galvanometer system to move the laser beam spot to the area of ​​the on-chip inductor on the wafer where the magnetic film is to be packaged.

[0052] (5) An infrared fiber laser with a wavelength of 1064 nm is used to irradiate the magnetic slurry on the printed inductor according to a pre-set scanning path to solidify it into a magnetic film and tightly bond it to the wafer.

[0053] The main processing parameters of the laser are: the working mode is continuous mode, the beam shape is Gaussian focus, the laser power is 0.2 W, the scanning speed is 280 mm / s, the number of scans is 1250 times, the scanning spacing is 25 μm, and the spot overlap rate is 75%.

[0054] Under this laser process parameter, the infrared thermal temperature diagram during laser curing of encapsulated magnetic film is as follows: Figure 2As shown in the figure, the maximum temperature is 123°C. The finished magnetic film after curing and encapsulation is as follows Figure 3 shown.

[0055] (6) The uncured magnetic slurry on the silicon wafer is removed by ultrasonic cleaning using anhydrous ethanol.

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

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

[0058] The performance of the planar inductor encapsulated with ferroferric oxide magnetic film was tested. The test results are as follows Figure 5 As shown, it can be seen that, compared with the same type of planar inductors, the inductance (L) and quality factor (Q) of the on-chip magnetic film inductor packaged by the method of this embodiment at 1 GHz are increased by 20.2% and 7% respectively. In long-term tests, the magnetic film packaged on the on-chip inductive element by laser direct writing has good reliability and consistency.

[0059] Example 2

[0060] The steps of the laser direct writing magnetic thin film packaging method for chip inductive elements provided in this embodiment are basically the same as those in embodiment 1, except that the laser used in this embodiment is an infrared laser with a wavelength of 1064 nm, and the operating parameters of the laser are laser power 0.4 W, scanning speed 280 mm / s, scanning times 1250 times, 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 of laser power has no obvious effect on the hysteresis characteristics of the packaged magnetic film.

[0061] Example 3

[0062] The steps of the laser direct writing magnetic thin film packaging method for chip inductive elements provided in this embodiment are basically the same as those in embodiment 1, except that the laser used in this embodiment is a 1064 nm wavelength infrared laser, and the operating parameters of the laser are laser power 0.2 W, scanning speed 250 mm / s, scanning times 1250 times, scanning spacing 25 μm, and spot overlap rate 75%. Figure 6 As shown in (b), the scanning speed of group A is 280 mm / s, and the scanning speed of group B is 250 mm / s. It can be seen that the change in scanning speed has no significant effect on the hysteresis characteristics of the packaged magnetic film.

[0063] Example 4

[0064] The steps of the laser direct writing magnetic thin film packaging method for chip inductive elements provided in this embodiment are basically the same as those in embodiment 1, except that the laser used in this embodiment is a 1064 nm wavelength infrared laser, and the working parameters of the laser are laser power 0.2 W, scanning speed 280 mm / s, scanning times 1500 times, scanning spacing 25 μm, and spot overlap rate 75%. Figure 6 As shown in (c), the scanning times of group A is 1250 times, and the scanning times of group B is 1500 times. It can be seen that the change of scanning times has no significant effect on the hysteresis characteristics of the packaged magnetic film.

[0065] Example 5

[0066] The steps of the laser direct writing magnetic thin film packaging method for chip inductive elements provided in this embodiment are basically the same as those 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 curing 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 magnetic film. The lower the content of magnetic particles, the lower the saturation magnetization intensity of the magnetic film. The higher the magnetic content of the magnetic film encapsulated on the inductive element, the more significant the improvement in device performance.

[0068] Example 6

[0069] The steps of the laser direct writing magnetic thin film packaging method for chip inductive elements provided in this embodiment are basically the same as those in Example 1, except that the curing adhesive used in this embodiment is a single-component phenolic resin thermosetting adhesive purchased from Gongyi Borun Refractory Materials Co., Ltd., and the product model is 2130.

[0070] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A laser direct writing magnetic thin film packaging method for chip inductive elements, characterized in that: The following steps are involved: The magnetic nanoparticles are mixed evenly with a curable adhesive to form a magnetic slurry, and the magnetic slurry is evenly coated on the chip with the inductive element; Using laser to irradiate the magnetic paste above the chip inductive element in a direction so that the magnetic paste is solidified to form a magnetic film and adhered to the chip; The uncured magnetic slurry on the chip is cleaned and removed, and a sensitive element encapsulated by a magnetic film is obtained on the chip.

2. The laser direct writing magnetic thin film packaging method of the chip inductive element according to claim 1 is characterized in that: Align the laser spot with the alignment mark of the chip to be processed, focus the laser spot on the surface of the chip to be processed; align the laser spot with the area of ​​the magnetic film to be packaged corresponding to the inductive element on the chip to be processed.

3. The laser direct writing magnetic thin film packaging method of the chip inductive element according to claim 1, characterized in that: The size of the magnetic nanoparticles is 5 nm-500 nm.

4. The laser direct writing magnetic thin film packaging method of the chip inductive element according to claim 1, characterized in that: The mass ratio of the magnetic nanoparticles to the curing adhesive is no more than 3:

4.

5. The laser direct writing magnetic thin film packaging method of chip inductive element according to claim 1, characterized in that: The curable adhesive is a high molecular polymer cured by laser irradiation.

6. The laser direct writing magnetic thin film packaging method of the chip inductive element according to claim 5, characterized in that: The curing adhesive is epoxy resin or phenolic resin.

7. The laser direct writing magnetic thin film packaging method of chip inductive element according to claim 1, characterized in that: The laser is an infrared laser or an ultraviolet laser.

8. The laser direct writing magnetic thin film packaging method of chip inductive element according to claim 1, characterized in that: The cleaning method is ultrasonic cleaning or plasma cleaning.

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