Soitec’s New eSI SOI Wafers For 4G/LTE (Now in High Volume Production) Used at Most Leading RF Foundries
Posted date : Dec 5, 2013

Soitec has reached high-volume manufacturing of our new Enhanced Signal Integrity™ (eSI) substrates, enabling cost-effective and high-performance RF devices. They are the first ‘trap-rich’ type of material in full production, and are already used in manufacturing by most of the leading RF foundries in front-end modules for 4G and LTE mobile computing and communication applications.

This is a major addition to our Wave SOI™  family of high-resistivity (HR) wafers for wireless applications. Our HR-SOI wafers have been used by market leaders for almost a decade, successfully addressing the challenges of 2G and 3G networks. But the data transfer rates of the new generation of 4G and LTE protocols called for a new substrate solution that would help designers meet the higher linearity and increased integration requirements.

Working together, Soitec and Université catholique de Louvain (UCL) developed a technique that adds a “trap-rich” layer underneath the buried oxide, which freezes the parasitic surface conduction that’s inherent in any oxidized silicon substrate. (The technical details are explained in a related post – click here to read it.) Using a set of very specific patents, Soitec applied proprietary technology and accumulated knowledge to build the new eSI product line.


A new generation of HR-SOI substrate: enhanced Signal Integrity™
(eSI) (Image courtesy of Soitec)

Because this layer is built at the substrate level, expensive process steps such as high-energy implant and conservative design rules are not required when designing on eSI wafers. The result is a cheaper process and potentially smaller die area per function.

The eSI substrate allows RF designers to integrate on the same chip diverse functions such as switches, power amplifiers and antenna tuners with excellent RF isolation, good insertion loss and better signal integrity than traditional technologies.

Here is a table outlining some of the major performance advances in front-end module integration that the eSI substrate enables:


The adoption of RF-SOI wafers for RF switches in handsets is now over 65 percent (Source: Yole Développement). The first RF-SOI power amplifiers and integrated front-end modules are being well received and gaining momentum in the market. Based on current levels of adoption and performance, increasing use of RF-SOI wafers for integrated front-end modules is expected to follow the same adoption rate as seen with switches.


Looking back over the mobile revolution, we have seen the ever-increasing pressure on smart phone and device manufacturers to support increased demand for data traffic. Moving forward requires the contributions of all players along the value chain, including substrate manufacturers.

SOI substrates are playing a major role in RF applications. Soitec’s eSI product, developed and fine tuned over the past few years, is now qualified by several key customers and is already being used in volume production of mobile handsets on today’s market. Together, we are enabling the cost-effective integration of more and more functions as well as higher data throughput, smaller size, better reliability, improved performance and lower system cost.




NOTE: This article was largely excerpted from a white paper entitled Innovative RF-SOI Wafers for Wireless Applications. To download the complete white paper, click here.


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