Three-dimensional spiral variable film inductor and preparation method thereof

Abstract

The invention belongs to the technical field of thin film inductors and magnetron sputtering, and particularly relates to a three-dimensional spiral variable thin film inductor and a preparation method thereof.The inductor comprises a runway type magnetic core, the magnetic core comprises a first long arm, a second long arm, a first short arm and a second short arm, the first long arm and the second long arm are oppositely arranged, and the first short arm and the second short arm are oppositely arranged; the plurality of first spiral coils are arranged on the first long arm; the plurality of second spiral coils are arranged on the second long arm; the two ends of each first spiral coil are provided with contacts, the adjacent first spiral coils are connected in series through a common contact located between the first spiral coils, the two ends of each second spiral coil are provided with contacts, and the adjacent second spiral coils are connected in series through a common contact located between the second spiral coils. The magnetic core is a high-entropy alloy magnetic core, the components of the high-entropy alloy comprise Zr and / or B, Fe, Co and Ni, each coil can be independently supplied with power through the contacts, or power can be supplied to a plurality of coils in a combined mode, and higher design and application flexibility is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of thin film inductor technology and magnetron sputtering technology, and in particular relates to a three-dimensional spiral variable thin film inductor and a preparation method thereof. Background Art

[0002] In recent years, driven by the product market, the key development trends in power electronics technology have been system miniaturization and system functionalization. The miniaturization of portable devices in the portable electronics market also requires the miniaturization of power management circuits (such as DC-DC converters). Discrete passive components, namely inductors and transformers, are typically the largest components in power systems. Miniaturized inductors enable a higher degree of system integration to realize power systems on chip (PwrSoC). Thin-film inductors, which utilize a new thin-film manufacturing technology for inductor devices and combine it with the application of high-performance magnetic materials, can meet these requirements.

[0003] Currently, due to the complexity of applications and the diversity of demand scenarios, major manufacturers offer a wide range of thin-film inductor models to meet the needs of different application scenarios. This undoubtedly increases the number of product varieties and leads to high R&D, design, and manufacturing costs. Therefore, it is of great significance to design a thin-film inductor structure with adjustable performance to expand the application scenarios of thin-film inductors and reduce development and manufacturing costs. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art, thereby providing a three-dimensional spiral variable thin film inductor and a preparation method suitable for multiple power requirements. The present invention proposes a thin film inductor structure, which adopts a racetrack-shaped magnetic core and arranges four spiral coils on each side of the runway. All the spiral coils adopt the same design, have the same number of winding turns and the same cross-sectional area. The four spiral coils on the same side are connected in series with each other, and each has five contact points, which can be flexibly contacted with the equipment. This structure has greater flexibility, and can not only power each spiral coil separately, but also be combined with each other to achieve inductance intermodulation. This design can be used for devices with more power designs, while reducing the variety and lowering costs.

[0005] The complete technical solution of the present invention includes: A three-dimensional spiral variable thin film inductor includes a racetrack-shaped magnetic core, the racetrack-shaped magnetic core including a first long arm and a second long arm arranged oppositely, a first short arm and a second short arm arranged oppositely, a plurality of first spiral coils arranged on the first long arm, and a plurality of second spiral coils arranged on the second long arm; each first spiral coil has contacts at both ends, and adjacent first spiral coils are connected in series via a common contact located between the two coils; each second spiral coil has contacts at both ends, and adjacent second spiral coils are connected in series via a common contact located between the two coils; The racetrack-shaped magnetic core is a high-entropy alloy magnetic core, and the components of the high-entropy alloy include Fe, Co, Ni, and Zr and / or B elements.

[0006] Furthermore, the number of the first spiral coils and the number of the second spiral coils are the same.

[0007] Furthermore, the first spiral coil and the second spiral coil have the same number of winding turns.

[0008] Furthermore, the first helical coil and the second helical coil have the same cross-sectional area.

[0009] Furthermore, each helical coil can be powered individually or a combination of multiple helical coils can be powered via the contacts.

[0010] Furthermore, the number of the first spiral coil and the number of the second spiral coil are both 4, and the number of contacts on the first spiral coil and the second spiral coil are both 5.

[0011] Furthermore, the composition and content range of the high entropy alloy are as follows: 1) Composed of Zr, Fe, Co, and Ni, with the content of each element ranging from 10.5 to 14.2 at%, 21.7 to 50.5 at%, 16.4 to 53.4 at%, and 12.3 to 22.1 at%; or 2) Composed of B, Fe, Co, and Ni, with the content of each element ranging from 7.5 to 12.1 at%, 20.3 to 54.5 at%, 13.5 to 58.5 at%, and 11.2 to 22.5 at%; or 3) It is composed of B, Zr, Fe, Co, and Ni elements, and the content range of each element is: B: 4.6~8.8at%, Zr: 2.7~6.5at%, Fe: 20.3~54.5 at%, Co: 13.5~58.5 at%, Ni: 11.2~22.5 at%.

[0012] Furthermore, the optimized component content of the high entropy alloy is determined by a high-throughput screening component design method.

[0013] Furthermore, by switching the contacts of the three-dimensional spiral variable thin film inductor, selecting different taps, and adjusting the effective number of turns of the inductor, the inductance value is controlled to realize applications with multiple inductance requirements.

[0014] Furthermore, the method for preparing the three-dimensional spiral variable thin film inductor includes the following steps: Step (1) sputtering a SiO2 layer on the substrate, obtaining a lower coil pattern by photolithography, magnetron sputtering a lower seed layer, and electroplating a lower copper coil on the lower seed layer; Step (2) then photolithographically patterns the lower copper pillar through holes and electroplates the lower copper pillars, removes the photoresist, and etches away the seed layer to obtain the lower copper wire layer and copper pillars; Step (3) spin coating the PI layer until the copper pillar is completely covered, and polishing the surface of the PI layer until the surface of the copper pillar is exposed; Step (4) photolithography of a high entropy alloy core pattern, and magnetron sputtering to obtain a high entropy alloy core layer; Step (5) preparing an upper copper pillar through-hole pattern and electroplating the upper copper pillar in the same manner as step (2); Step (6) prepare the upper copper coil and contact PAD in the same manner as step (1); Step (7) etching away the upper seed layer to obtain a three-dimensional spiral variable thin film inductor.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) Greater flexibility in design and application: This structure can be flexibly adjusted according to different demand scenarios, and can meet the design requirements in various scenarios. At the same time, the inductor device with this structure has greater application flexibility. Each coil can be powered separately, or they can be combined with each other to achieve inductance intermodulation. This design can be used for devices with more power designs, reducing the variety of products and reducing R&D and manufacturing costs.

[0016] (2) The spiral structure can achieve greater inductance: Compared with simple planar spiral inductors, the coils are located in the same plane. Due to limited space, the number of coils is relatively limited, and the improvement in inductance is relatively limited. In contrast, the three-dimensional spiral inductor increases the number of coils, which is more conducive to obtaining a larger inductance value and improving the overall performance of the inductor.

[0017] (3) Compatible with semiconductor technology and suitable for mass industrial production: The manufacturing process adopts thin film technology and semiconductor technology, which has good compatibility, diverse application scenarios, high adjustability, and is suitable for mass-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. 4 is a plan view of a three-dimensional spiral variable thin film inductor according to the present invention.

[0019] Figure 2 This is a three-dimensional diagram of the three-dimensional spiral variable thin film inductor of the present invention.

[0020] Figure 3 Schematic diagram of a spiral coil.

[0021] In the figure, 1 is a magnetic core, 2 is a first spiral coil, 3 is a second spiral coil, 4 is a first contact, and 5 is a second contact. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the embodiments and accompanying drawings. However, it should be understood that the embodiments and accompanying drawings are merely exemplary descriptions of the present invention and do not constitute any limitation on the scope of protection of the present invention. All reasonable variations and combinations within the scope of the inventive concept of the present invention fall within the scope of protection of the present invention.

[0023] like Figure 1-Figure 3 As shown, the present invention discloses a three-dimensional spiral variable thin film inductor suitable for multiple power requirements, including a racetrack-shaped magnetic core 1, wherein the magnetic core includes a first long arm and a second long arm arranged oppositely, a first short arm and a second short arm arranged oppositely, a plurality of first spiral coils 2 arranged on the first long arm, and a plurality of second spiral coils 3 arranged on the second long arm; the number of first spiral coils and the second spiral coils are the same, the first spiral coils and the second spiral coils have the same number of winding turns and cross-sectional area, each first spiral coil is provided with a first contact 4 at both ends, and adjacent first spiral coils are connected in series via a common first contact located in the middle of the two, each first spiral coil is provided with a second contact 5 at both ends, and adjacent second spiral coils are connected in series via a common second contact located in the middle of the two; preferably, the number of first spiral coils and second spiral coils is 4, and the number of contacts on the first spiral coil and the second spiral coil is 5.

[0024] The three-dimensional spiral variable thin film inductor of the present invention can power each spiral coil individually or power multiple spiral coils in combination through contacts. Specifically: Inductance calculation formula:

[0025] Where, L is the inductance [H], K is the Nagaoka coefficient, μ is the magnetic permeability, N is the number of coil turns, S is the cross-sectional area of ​​the coil [m 2 ], is the coil length [m].

[0026] Since the inductance L is proportional to the square of the number of coil turns N (L∝N 2 By switching the contacts of the three-dimensional spiral variable thin-film inductor to select different taps, the effective number of turns of the inductor can be adjusted, thereby precisely controlling the inductance value to meet various inductance requirements. For example, if the total number of turns is 100, when the contact is connected to the 80th turn, the inductance is approximately 64% of the total number of turns.

[0027] inductance L Proportional to the square of the permeability of the racetrack core (L∝ The core's excellent soft magnetic properties contribute to improved inductance performance. The high-entropy alloy core employed in this invention possesses both excellent soft magnetic properties and high resistivity. This high resistivity reduces eddy current losses, lowering overall device losses and heat generation, thereby ensuring device stability.

[0028] In the present invention, the optimal composition of the high entropy alloy used in the racetrack-type magnetic core is determined by a high-throughput screening composition design method. To illustrate the alloy composition optimization process of the present invention, the high-throughput screening method adopted is further described.

[0029] (1.1) Multi-component gradient thin film sputtering: Using the magnetron sputtering process, the chamber atmosphere conditions are controlled, and the various component elements of the high-entropy alloy target are deposited on the surface of each substrate through magnetron sputtering to obtain multiple thin film samples with different component contents.

[0030] First, the preset range of the content of each component element determined by the present invention is: 1) Zr: 10.5~14.2 at%, Fe: 21.7~50.5 at%, Co: 16.4~53.4 at%, Ni: 12.3~22.1at%; or 2) B: 7.5~12.1 at%, Fe: 20.3~54.5 at%, Co: 13.5~58.5 at%, Ni: 11.2~22.5 at%; or 3) B: 4.6~8.8 at%, Zr: 2.7~6.5 at%, Fe: 20.3~54.5 at%, Co: 13.5~58.5 at%, Ni: 11.2~22.5 at%; During this process, in order to ensure that the component content of the thin film samples is within a preset range and that the content of each component in each sample varies as evenly as possible to facilitate subsequent high-throughput screening, the different atomic binding forces of each target during sputtering lead to different atomic detachment rates. This paper analyzes the spatial distribution pattern of the atoms of each target after detachment (with increasing distance from the target, the concentration of target element atoms in space gradually decreases). The analysis identifies the main influencing factors (the total number of samples, the horizontal spacing and the vertical spacing of each sample), and selects the following experimental method: High-purity Fe, high-purity Co, high-purity Ni, and high-purity M targets are used and evenly placed at four positions in the chamber. The M target is a Zr target, a B target, or a mixed target of Zr and B. The angles of the four target positions are adjusted to form a 45° angle with the horizontal. The sample holder is placed in the middle of the four targets, and multiple high-resistivity non-magnetic material substrates are placed on the sample holder.

[0031] First, we select the same sample with a fixed sputtering time t0 and a fixed distance d0 from the target. We then measure the deposition thickness of each target element on the sample surface at different powers to characterize its desorption rate at different powers. Then, using Fe as a benchmark, we determine the baseline sputtering power (250W) for the Fe target and the desorption rate of Fe at this power. Then, we select corresponding powers for other components so that their desorption rates at the corresponding sputtering powers meet the following equation:

[0032] Where: For ingredients The desorption rate at the selected corresponding power is, is the desorption rate of Fe component at the reference sputtering power, For ingredients The minimum atomic percentage content within the preset content range, For ingredients The maximum atomic percentage content within the preset range, is the minimum atomic percentage content of Fe within the preset range, It is the maximum atomic percentage content of Fe within the preset range.

[0033] When M is a Zr target or a B target, the maximum and minimum atomic percentages of the M component are the maximum and minimum atomic percentages of the Zr and B elements, respectively. When M is a Zr / B mixed target, the maximum atomic percentage of the M component is the sum of the maximum atomic percentages of the Zr and B elements, and the minimum atomic percentage of the M component is the sum of the minimum atomic percentages of the Zr and B elements.

[0034] The sample placement parameters (horizontal spacing, vertical spacing, and number) were then determined. Fe and M targets were selected, and the deposition rates (the ratio of deposition thickness on the substrate surface to deposition time) of the closest sample and the furthest sample were measured under different sample spacing (horizontal spacing, vertical spacing) and sample numbers. The attenuation of these rates was statistically analyzed, and multiple linear regression was used to determine the relationship between the attenuation and the horizontal and vertical spacing, and number of samples. When M was a Zr target and a B target, the deposition rates of the Zr and B elements were calculated and analyzed separately. When it was a Zr / B mixed target, the total deposition rate of the two elements was calculated and analyzed.

[0035] According to the obtained relationship, the corresponding sample spacing and number are selected so that:

[0036]

[0037] Where, is the maximum value of the atomic percentage ratio of Fe component to M component within the preset range, This is the maximum atomic percentage ratio of the M component to the Fe component within a preset range during high-throughput testing. Similarly, when M is a Zr target or a B target, the maximum and minimum atomic percentages of the M component are the maximum and minimum atomic percentages of the Zr and B elements, respectively. When it is a Zr / B mixed target, the maximum atomic percentage of the M component is the sum of the maximum atomic percentages of the Zr and B elements, and the minimum atomic percentage of the M component is the sum of the minimum atomic percentages of the Zr and B elements. is the deposition rate of Fe atoms on the sample closest to the Fe target, is the deposition rate of Fe atoms on the sample farthest from the Fe target; is the deposition rate of M atoms on the sample closest to the M target, is the deposition rate of M atoms on the sample farthest from the M target.

[0038] The parameters finally selected are: horizontal spacing 2.5cm, vertical spacing 1.3cm, and number 60.

[0039] (1.2) Sample testing and target material composition design: Multiple thin film samples are tested and the specific contents of the constituent elements of high-entropy alloys and high-entropy alloy targets are screened based on the saturation magnetization, coercive force, and resistivity performance requirements.

[0040] After the target material is prepared, it is cut and then heat treated. In terms of the target cutting size and heat treatment process, a response surface model is constructed for experimental design, and the optimized parameter combination is obtained based on the experimental results. The selected controllable variables include: target cutting thickness X1, with a value range of 10~20mm; target cutting diameter X2, with a value range of 100~150mm; number of heat treatments X3, with a value range of 1~3 times; heat treatment temperature X4, with a value range of 700~1000℃; heat treatment time X5, with a value range of 1~15 hours.

[0041] The degree of deviation in component content, Y, was selected as the response variable. Factor levels were coded, and actual experimental parameters were constructed based on the coded values ​​of each designed experiment. Designs that did not meet actual requirements were removed, and a central composite experimental design was performed. Multiple groups of experiments were conducted, and the degree of deviation in component content, Y, was measured and calculated for each group of experiments. A second-order polynomial regression model based on the degree of deviation in component content and controllable variables was established. The coefficient estimates of the regression model were obtained using the least squares method. The predicted degree of deviation in component content, Y, obtained from the regression model, was used as the objective function, with the goal of minimizing Y. An initial solution was set and iterative optimization was performed. When the maximum number of iterations was reached, the current solution was used as the optimized parameter combination. Specifically, the target cutting diameter was 142 mm, the cutting thickness was 16 mm, and a two-stage heat treatment process was used. The first stage heat treatment temperature was 820°C, the heat treatment holding time was 10 h, and the second stage heat treatment temperature was 980°C, the heat treatment holding time was 1.5 h.

[0042] The above-mentioned inert gas plus two-stage homogenization heat treatment method is adopted. The first-stage heat treatment temperature is lower than the second-stage heat treatment temperature, and the heat treatment time is longer. While ensuring a good homogenization effect, it avoids local overburning and abnormal grain enlargement caused by long-term high-temperature insulation.

[0043] The preparation method of the three-dimensional spiral variable thin film inductor of the present invention is as follows: S1. Substrate preparation: Use a high-resistance silicon substrate and sputter a SiO2 layer about 1μm thick to reduce substrate loss.

[0044] S2. Photolithography of the lower copper coil: Spin-coating photoresist, baking, exposure, and development are performed to obtain the lower copper coil pattern.

[0045] S3. Seed layer sputtering: Sputtering Ti / Cu seed layer to improve the adhesion of electroplated copper.

[0046] S4. Electroplating of the lower copper coil: Electroplating a copper layer on the seed layer with a plating current density of 20mA / cm 2 , time is 10 minutes.

[0047] S5. Remove the photoresist.

[0048] S6. Copper pillar via patterning: spin coating of photoresist, resist baking, exposure, and development.

[0049] S7. Electroplating copper pillars.

[0050] S8. Remove the photoresist and etch away the Cu seed layer to obtain the underlying copper wire layer and copper pillars.

[0051] S9. Apply a thick polyimide (PI) layer and polish: Spin-coat the PI layer until it completely covers the copper pillars. Polish the surface of the PI layer until the copper pillars are clearly visible.

[0052] S10. Photolithography of the high-entropy alloy core layer: The high-entropy alloy core pattern is obtained through spin coating of photoresist, baking, exposure, and development.

[0053] S11. Magnetron sputtering of high entropy alloy core layers.

[0054] S12. Photolithography of copper pillar through-hole pattern and electroplating of copper pillars, thick coating of PI layer and polishing: the steps are the same as S6, S7 and S8.

[0055] S13. Photolithography of the upper copper coil and contact pad shape: Spin-coating photoresist, baking, exposure, and development steps to obtain the upper copper coil and contact pad shape pattern.

[0056] S14. Copper plating preparation and post-processing of the upper copper coil and contact PAD: Perform the same steps as S3, S4, and S5.

[0057] S15. Etching away the seed layer to obtain a three-dimensional spiral variable thin film inductor.

[0058] Those skilled in the art will readily recognize other embodiments of the present disclosure after considering the disclosure in the specification and examples. The present invention is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the claims.

Claims

1. A three-dimensional spiral variable thin film inductor, characterized in that: The racetrack-shaped magnetic core includes a first long arm and a second long arm arranged opposite to each other, a first short arm and a second short arm arranged opposite to each other, a plurality of first spiral coils arranged on the first long arm, and a plurality of second spiral coils arranged on the second long arm; each first spiral coil is provided with contacts at both ends, and adjacent first spiral coils are connected in series via a common contact located between the two coils; each second spiral coil is provided with contacts at both ends, and adjacent second spiral coils are connected in series via a common contact located between the two coils; The racetrack-shaped magnetic core is a high-entropy alloy magnetic core, and the components of the high-entropy alloy include Fe, Co, Ni, and Zr and / or B elements.

2. The three-dimensional spiral variable thin film inductor according to claim 1, characterized in that: The number of the first helical coils and the number of the second helical coils are the same.

3. The three-dimensional spiral variable thin film inductor according to claim 2, characterized in that: The first helical coil and the second helical coil have the same number of winding turns.

4. The three-dimensional spiral variable thin film inductor according to claim 3, characterized in that: The first helical coil and the second helical coil have the same cross-sectional area.

5. The three-dimensional spiral variable thin film inductor according to claim 4, characterized in that: Each helical coil can be powered individually or a combination of multiple helical coils can be powered via the contacts.

6. The three-dimensional spiral variable thin film inductor according to claim 5, characterized in that: The number of the first spiral coil and the number of the second spiral coil are both four, and the number of contacts on the first spiral coil and the second spiral coil are both five.

7. The three-dimensional spiral variable thin film inductor according to claim 6, characterized in that: The constituent elements and content ranges of high entropy alloys are: 1) Composed of Zr, Fe, Co, and Ni, with the content of each element ranging from 10.5 to 14.2 at%, 21.7 to 50.5 at%, 16.4 to 53.4 at%, and 12.3 to 22.1 at% for Zr; or 2) Composed of B, Fe, Co, and Ni, with the content of each element ranging from 7.5 to 12.1 at%, 20.3 to 54.5 at%, 13.5 to 58.5 at%, and 11.2 to 22.5 at%; or 3) It is composed of B, Zr, Fe, Co, and Ni elements, and the content range of each element is: B: 4.6~8.8 at%, Zr: 2.7~6.5 at%, Fe: 20.3~54.5 at%, Co: 13.5~58.5 at%, Ni: 11.2~22.5 at%.

8. The three-dimensional spiral variable thin film inductor according to claim 7, characterized in that: The content of each component of the high entropy alloy is determined by a high-throughput screening component design method.

9. The three-dimensional spiral variable thin film inductor according to claim 8, characterized in that: By switching the contacts of the three-dimensional spiral variable thin film inductor, selecting different taps, and adjusting the effective number of turns of the inductor, the inductance value is controlled to realize applications with multiple inductance requirements.

10. The method for preparing the three-dimensional spiral variable thin film inductor according to claim 9, characterized in that: The steps include: Step (1) sputtering a SiO2 layer on the substrate, obtaining a lower coil pattern by photolithography, magnetron sputtering a lower seed layer, and electroplating a lower copper coil on the lower seed layer; Step (2) then photolithographically patterns the lower copper pillar through holes and electroplates the lower copper pillars, removes the photoresist, and etches away the lower seed layer to obtain the lower copper wire layer and copper pillars; Step (3) spin coating the PI layer until the copper pillar is completely covered, and polishing the surface of the PI layer until the surface of the copper pillar is exposed; Step (4) photolithography of a high entropy alloy core pattern, and magnetron sputtering to obtain a high entropy alloy core layer; Step (5) prepares an upper copper pillar through-hole pattern and electroplates the upper copper pillar in the same manner as step (2); Step (6) prepare the upper copper coil and contact PAD in the same manner as step (1); Step (7) etching away the upper seed layer to obtain a three-dimensional spiral variable thin film inductor.

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