RF performances of inductors integrated on localized p+-type porous silicon regions

Marie Capelle,Jérôme Billoué,Patrick Poveda,Gaël Gautier

doi:10.1186/1556-276x-7-523

Abstract

To study the influence of localized porous silicon regions on radiofrequency performances of passive devices, inductors were integrated on localized porous silicon regions, full porous silicon sheet, bulk silicon and glass substrates. In this work, a novel strong, resistant fluoropolymer mask is introduced to localize the porous silicon on the silicon wafer. Then, the quality factors and resonant frequencies obtained with the different substrates are presented. A first comparison is done between the performances of inductors integrated on same-thickness localized and full porous silicon sheet layers. The effect of the silicon regions in the decrease of performances of localized porous silicon is discussed. Then, the study shows that the localized porous silicon substrate significantly reduces losses in comparison with high-resistivity silicon or highly doped silicon bulks. These results are promising for the integration of both passive and active devices on the same silicon/porous silicon hybrid substrate.

Highlights

The tremendous growth of mobile and wireless applications during the past decade has accelerated the development of radiofrequency (RF) technologies
The results show that frequency for one maximum quality factor (Qmax) is reached (fQmax) obtained with localized Porous silicon (PS) are lower than the ones with full PS sheet (Table 1)
To study the influence of hybrid substrate on the performances of passive devices, inductors have been integrated on localized PS and were characterized

Summary

Introduction

The tremendous growth of mobile and wireless applications during the past decade has accelerated the development of radiofrequency (RF) technologies. More and more radio frequency-integrated circuits (RFICs) have been integrated on a single chip, with the advantage of high density of the package, low cost and small volume. To integrate both active and passive devices and to reduce substrate losses, RFIC integration could be made on substrates such as silicon on glass [1], silicon on sapphire or high-resistivity silicon (HR Si) [2,3]. CMOS processes generally require low-resistivity silicon substrates, which are lossy and responsible for the deterioration of RF performances [3]. An alternative solution is the use of silicon/porous silicon hybrid substrates. Ben Chorin and co-workers measured a conductivity modification from 10−8 to 10−5/Ω cm from direct current (DC) signal

Methods

Results

Conclusion