While LED is the largest market for sapphire, there are several other emerging markets that take advantage of the physical attributes of sapphire. We’ll take a look at these emerging markets over the next month or so. We will begin with Silicon on Sapphire (SoS) for the RFIC market.
SoS is a part of the Silicon on Insulator (SOI) family of CMOS (Complementary metal–oxide–semiconductor) technology for making integrated circuits. SoS improves performance and integration for RF circuits. The holy grail of the wireless industry has been finding a better way to optimize power consumption and real estate utilization in mobile phones. One application for SoS technology is the production of RF chips used in the antenna switch in smart phones. These SoS chips are significantly smaller and use less power than chips traditionally used for this application. As a result, chips produced using SoS technology are rapidly gaining market share in the mobile phone industry.
Peregrine Semiconductor is a pioneer in SoS and holds much of the industry’s IP in SoS. In an interview with EE Times in 2011, Dr. Ronald E. Reedy, Peregrine co-founder said, “SoS is the first and most successful form of SOI focused entirely on improving performance and integration for RF circuits. We saw the emerging need for such a technology when commercial wireless communications started taking off in the early 1990s.”
What makes sapphire so good for SoS? Peregrine summarized it in a paper on the history on SoS. Sapphire and silicon have a unique way of lining up together at an atomic level because of oxygen atoms. The scientific explanation is that the r-plane of sapphire has oxygen atoms spaced at a distance that is close to the spacing of the atoms in the (100) plane of a silicon crystal. The spacing delivers unique insulating properties when the silicon is layered on top of the sapphire wafer. This was discovered by researchers at Boeing in 1963. Researchers at RCA continued the development of SoS technology into the mid-1970s and continue to process them for space applications.
Technological barriers leading to defects held SoS back from commercial applications until just recently. Peregrine has been able to overcome these hurdles at just the right time as the wireless industry needs the insulating and power saving benefits of SoS for the latest generations of smart phones. You’ll find more coverage of the emerging market in posts to come.
For Further Reading:
Electronics Weekly, Peregrine: Single chip phone RF is possible http://www.electronicsweekly.com/Articles/14/02/2012/52966/peregrine-single-chip-phone-rf-is-possible.htm
EE Times, What’s up with silicon on sapphire?, http://www.eetimes.com/design/microwave-rf-design/4216449/What-s-up-with-silicon-on-sapphire-
Peregrine Semiconductor Corporation, The History of Silicon on Sapphire, www.psemi.com/articles/History_SOS_73-0020-02.pdf