Monolithic integration of BST thin film varactors and Au electroplated thick film inductors above IC

Sho Asano, Ramesh Pokharel, Awinash Anand, Hideki Hirano, Shuji Tanaka

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


This paper presents an integration process of barium strontium titanate (BST) thin film varactors and Au thick film inductors above an integrated circuit (IC) by film transfer technology and Au electroplating process. A high-quality BST film grown on a Si substrate at 650°C was patterned into MIM (Metal-Insulator-Metal) structures, and transferred to an IC substrate at 270°C by BCB (Benzocyclobutene) polymer bonding and Si lost wafer process. Thick film inductors fabricated by Au electroplating were also integrated above the IC substrate to realize high Q factor. The capacitance tunability of the BST varactors did not decrease by transfer process. The Q factor of the fabricated inductor was higher than that of conventional inductors on IC chips. The resonant frequency of an LC series resonance circuit composed of the transferred BST varactor and the Au electroplated inductor changed from 0.76 GHz to 1.19 GHz by applying a DC bias voltage of 8 V to the BST varactor. Monolithic integration technology developed in this research will be useful for tunable radio frequency circuits like tunable power amplifiers.

Original languageEnglish
Pages (from-to)323-329
Number of pages7
JournalIEEJ Transactions on Sensors and Micromachines
Issue number8
Publication statusPublished - Aug 1 2015

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Electrical and Electronic Engineering


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