A Silicon-Embedded Transformer for High-Efficiency, High-Isolation, and Low-Frequency On-Chip Power Transfer

In this brief, a backside silicon-embedded transformer (BSET) with an improved isolation structure is proposed and demonstrated. The interleaved transformer coils are embedded inside a silicon substrate from the backside and connected to the front-side through vias. The isolation between the coils is achieved by the oxide layer between the Cu coil and the Si substrate, as well as the BCB (BenzoCycloButene) layer covering the backside of the transformer. The 2-mm2 BSET fabricated shows a best reported monolithic transformer efficiency of over 80% at a low frequency of 20 MHz. A 380 V isolation capability is achieved and shows the potential for various applications, such as USB (Universal Serial Bus) isolation. Only three masks are required for the fabrication. This technology is very suitable for on-chip isolated power transfer applications.

[1]  Nian X. Sun,et al.  High-Bandwidth Low-Insertion Loss Solenoid Transformers Using FeCoB Multilayers , 2013, IEEE Transactions on Power Electronics.

[2]  Shizhi Wang,et al.  Diffusion barrier properties of TiW between Si and Cu , 1993 .

[3]  Ningning Wang,et al.  High efficiency Si integrated micro-transformers using stacked copper windings for power conversion applications , 2012, 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[4]  Rongxiang Wu,et al.  High-Q Backside Silicon-Embedded Inductor for Power Applications in /spl mu/H and MHz Range , 2013, IEEE Transactions on Electron Devices.

[5]  S. Bedair,et al.  High-Inductance-Density, Air-Core, Power Inductors, and Transformers Designed for Operation at 100–500 MHz , 2010, IEEE Transactions on Magnetics.

[6]  Rongxiang Wu,et al.  A Novel Silicon-Embedded Coreless Inductor for High-Frequency Power Management Applications , 2011, IEEE Electron Device Letters.

[7]  Rongxiang Wu,et al.  A novel silicon-embedded coreless transformer for isolated DC-DC converter application , 2011, 2011 IEEE 23rd International Symposium on Power Semiconductor Devices and ICs.

[8]  Baoxing Chen,et al.  Fully integrated isolated dc-dc converter using micro-transformers , 2008, 2008 Twenty-Third Annual IEEE Applied Power Electronics Conference and Exposition.