- freely available
Micromachines 2017, 8(5), 151; https://doi.org/10.3390/mi8050151
2. Model Design and Simulation
2.1. Effect of Patterned Magnetic Film on the Performances of Micro-Inductor
2.2. Effect of Magnetic Film Thickness on the Performances of Micro-Inductor
3. Fabrication and Characterization
3.1. Fabrication of the Planar Inductor
- The glass wafer was selected as the substrate. Cr/Cu metal was sputtered on the substrate as the first seed layer as the Cr can enhance the adhesive force between Cu and glass substrate. Photoresist was spin coated on the seed layer and patterned by lithography and development. The bottom magnetic film (Ni80Fe20) was electroplated on Cr/Cu seed layer (thickness 20 µm).
- The sodium hydroxide solution (4%) was used to remove the residual photoresist, and an ammonia/peroxide solution was used to remove the chromium/copper seed layers. The polyimide was selected as the insulation layer for filling spacing of the single coil after the photoresist and the seed layer was removed, respectively.
- Another Cr/Cu seed layer was sputtered and another layer of photoresist was spin coated and patterned. The bottom planar coil and the via connecting the two layer of coils was fabricated by electroplating process (thickness 20 µm), respectively.
- The sodium hydroxide solution (4%) was used to remove the residual photoresist. The third layer of photoresist was spin coated and patterned. The via was further electroplated to a higher position than the bottom coil in order to connect the top coil (Cu 5 µm). The pad was also fabricated by multi-step electroplating process.
- The residual photoresist and the Cr/Cu seed layer was removed, respectively. The polyimide was also used as the insulation layer between two layers of the coil.
- The third Cr/Cu seed layer was sputtered and the fourth layer of photoresist was spin coated and patterned. The top planar coil was electroplated (thickness 20 µm).
- The fourth Cr/Cu seed layer was sputtered and the fifth layer of photoresist was spin coated and patterned to electroplate the pad (Cu 5 µm).
- The sixth layer of photoresist was spin coated and patterned. The top magnetic film was electroplated (thickness 20 µm). Acetone was used to remove the positive photoresist, and ammonia/peroxide solution was chosen to remove the seed layer.
3.2. Application of the Micro-Inductor in a Buck DC/DC Converter
4. Results and Discussion
4.1. Electrical Properties of the Fabricated Micro-Inductors
4.2. Characteristics of Analog Circuit Testing
Conflicts of Interest
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|Types||Copper Square Spiral Coil||Magnetic Films|
|Number of Tums (N)||Thickness (tc)||Line Width (wc)||Spacing (S)||Material (M)||Thickness (ts)||Outer Dimension|
|1||17||20 μm||20 μm||20 μm||-||-||-|
|2||Permalloy||10 μm||1.9 mm × 1.9 mm|
|3||Permalloy||20 μm||1.9 mm × 0.12 mm × 12 mm|
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