MST Boosts RF-SOI Capabilities to Solve Key 5G Challenges
By Robert Mears, Atomera Founder and CTO
Not very long ago, in 2G and 3G smart phones, the main application of an RF switch was to make efficient use of components for switching between simple transmit and receive functions. Much more is being asked of RF switches for the upcoming generation of 5G smart phones. The number of RF switches has multiplied to support more high frequency bands and they are being integrated with other RF components such as low-noise amplifiers (LNAs) and even power amplifiers (PAs) to maintain signal integrity.
RF-SOI is the key semiconductor technology for RF switches and, more recently, for integrating RF-switches with LNA and PA functionality. But it is under growing pressure to deliver the performance characteristics that are required in 5G applications. Two of the most vexing challenges in 5G devices are: (1) Ron-BVDSS (the trade-off between the ON resistance and the breakdown voltage) and (2)better Ron-Coff (the trade-off between the ON resistance and the off-state capacitance). Atomera’s MST enables RF-SOI technology to solve these tradeoffs.
Once a niche technology for simple switches, RF-SOI is now set for very strong growth as a key enabling technology for 5G. Indeed, the RF component content of a mobile phone has risen ten-fold, from around $2 per phone to close to $20 for a 5G phone*, and projections show continued double-digit growth. MST will enable RF-SOI technology to clear the next hurdle for its successful adoption in 5G switches: meeting the increased integration requirements by minimizing power losses from the ON resistance while increasing bandwidth (lower Coff).
More than ten years ago, our first MST publication was on SOI technology. With authors from Texas Instruments and Sematech (ATDF) in Austin, we demonstrated significant improvement in carrier mobility and drive current (Idlin – up to 30% enhancement) for 90nm partially-depleted silicon on buried oxide substrates (PD-SOI). At the time, the market for PD-SOI was small. Over the last few years, however, the PD-SOI technology has been further developed by SOITEC, making the technology much better suited to integrating RF switches and other RF devices. MST is both complementary and additive to SOI technology.
MST improves Ron-BVDSS and Ron-Coff to give RF-SOI a double boost, right where it’s so critically needed. The improved Idlin translates directly to a lower Ron at the same breakdown voltage. This is very good, but what makes it a “killer application” is that the MST technology can be used at the same time to engineer the device doping profiles (see my earlier blog posts). This improves the breakdown voltage and, most importantly for RF applications, reduces Coff. And all this in a competitive market, where a 10% improvement in Ron-BV is considered highly significant.
Atomera believes its MST technology is very well positioned to make a major impact in the 5G RF market. It will give RF-SOI technology the double boost it needs to fulfill its promise for solving 5G RF switching challenges.
* Mark Lapedus “RF-SOI wars begin” Semiconductor Engineering May 17, 2018
** John Pellerin, Global Foundries Keynote Presentation EDTM, March 1, 2017.