An analysis of perfect-magnetic-coupling ultra-low-loss micromachined SMIS RF transformers for RFIC applications
Journal
IEEE Transactions on Microwave Theory and Techniques
Journal Volume
54
Journal Issue
12
Pages
4256-4267
Date Issued
2006
Author(s)
Abstract
Selective removal of the silicon underneath a set of single-turn multilayer interlaced stacked (SMIS) radio-frequency (RF) transformers with nearly perfect magnetic-coupling factor (k IM ~1) and high resistive-coupling factor (k Re ) is demonstrated. This process is based on the inductively coupled-plasma (ICP) deep trench technology. Improvement of 20.6 and 15.7 dB in isolation (S 21 ) were achieved at 5.2 and 8 GHz, respectively, for a dummy open device after the backside ICP etching. Q-factor increases of 102% (from 4.96 to 10.03) and 23.2% (from 2.24 to 2.76), G Amax increases of 11.8% (from 0.76 to 0.85) and 4.5% (from 0.88 to 0.92), and NF min decreases of 0.49 dB (from 1.22 to 0.73 dB) and 0.19 dB (from 0.55 to 0.36 dB) were achieved at 5.2 and 8 GHz, respectively, for an SMIS transformer with an overall dimension of 170times240 mum 2 after the backside ICP etching. The G Amax of 0.85 and 0.92 are both state-of-the-art results among all reported on-chip transformers. Furthermore, the reasons why the SMIS transformer exhibits better performances than the traditional bifilar and the traditional stacked transformer are explained. These results show that the micromachined SMIS transformers are very promising for RF integrated circuit applications
Type
journal article