A 3D Assembled Silicon-Embedded Transformer for 10-MHz, Ultra-High-Isolation, Compact Chip-to-Chip Power Transfer

In this letter, a 3D assembled silicon-embedded transformer (3DASET) is proposed and demonstrated for low-frequency, ultra-high-isolation, compact power transfer applications. The primary and secondary coils of the 3DASET are embedded inside the primary side and secondary side chips, respectively, from the backside to achieve a large coil thickness and a whole-area utilization for each coil, as well as simple fabrication and compact integration. The two chips are then back-to-back bonded, and ultra-high isolation can be achieved with a sufficiently strong and thick isolation layer between the chips. The 2-mm
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3DASET fabricated can work at a low frequency of 10 MHz with a reasonable efficiency of 70%, which is essential for reducing the switching and rectifying losses of the system. A high isolation capability of over 4.5 kV can also be achieved.