Microtransformer on silicon with CoFeB magnetic core for high-frequency signal applications

Abstract

This paper presents the development, characterization and application of a microtransformer with a bar magnetic core fabricated on silicon substrate using thin-film technology. The magnetic core, coils, and insulation layers were deposited using only sputtering PVD (physical vapor deposition) or CVD (chemical vapor deposition) processes. As insulation materials, silicon dioxide and silicon nitride are only used. The device is small with a chip size of 1600 µm x 800 µm. The transformer has a turns ratio of 1:1 and achieves a self-inductance of about 40 nH. The minimum measured breakdown voltage of the microtransformer is 1250 V(DC). The microtransformer device is applicable for frequencies up to 20 MHz. The device was fabricated on 12-inch silicon substrates on mass production equipment.

A Survey on Microtransformers

“…This kind of geometry yields good coupling coefficients (higher than 80% in most of the devices analyzed) and can achieve high quality factors (Qvalues up to 27 have been reported) [49]- [51], [54]- [57], [60], [65], [67], [68]. On the other hand, microtransformers using this geometry are usually assembled using 1:1 or 1:2 turn ratios, having low inductance values [49], [55], [58], [67], [69]. This can mainly be attributed to the low number of turns in coreless windings.…”

Structure and Performance Optimization of Co Magnetic Thin Films Deposited by Vacuum Evaporation Coating

“…Magnetic materials are important functional materials that are widely used for energy conversion [1,2], data sensing [3], data processing [4], and information storage [5][6][7]. Magnetic thin film materials and devices are especially important for information storage [8][9][10][11][12][13].…”