RFMD (North Carolina, USA) is a global leader in the design and manufacture of high-performance radio systems and solutions for applications that drive mobile communications. In particular, RFMD supplies nearly 50% of all RF power amplifier (PA) modules used in cellular handsets.

Currently, these cellular PA modules use a combination of technologies:

- GaAs HBT or PHEMTs for the RF power amplifiers,

- high voltage silicon CMOS for the power management,

- and GaAs PHEMT technology for the RF high power switches.

The challenge, however, is that next generation (3G/4G) multi-band multi-mode systems will require several additional PA functions, which creates a definite problem from a size, cost and technology proliferation point of view

RFMD, in joint collaboration with Jazz Semiconductor (California, USA), has developed a silicon SOI-based technology to potentially integrate all of these three key PA module functions (amplification, power management and RF switching) into one monolithic and cost-effective die.

This technology utilizes what we call ‘Thick Film Silicon-on-Insulator’ (TF-SOI) substrates engineered by Soitec.

Because these three key RF functions require a high degree of RF isolation amongst themselves, the substrates are also built on high resistivity (HR) (1 kOhm-cm) silicon substrates. In addition to isolating the silicon semiconductor devices, the high resistivity substrates also allow us to obtain superior performance for our integrated passive components, like capacitors, resistors and transmission lines.

The technology was presented at the recent 2007 International Microwave Symposium in Hawaii in two separate papers.

Our TF-SOI technology includes the integration of an RF Power LDMOS transistor capable of nearly comparable linear and saturated RF power characteristics to GaAs solutions in the frequency range between 0.8-2.4GHz.

At this time, we are working very actively in the characterization of these highly integrated PA circuits. Expect very exciting news from RFMD regarding this TF-SOI technology effort in the near future!

Freescale’s PowerQUICC® family of integrated communications processors go into the world’s leading enterprise routers, wireless LANs, base stations, media gateways, network storage and industrial electronics. For us, that means ensuring the highest level of integration possible with the greatest flexibility to the customer while meeting reliability metrics at the lowest power.

Our customers are developing new generations of networking infrastructure equipment and solutions. They need processors that offer ultra-high performance, multiple system interface options, and outstanding price-to-performance ratios in a small footprint. This is in the face of evershrinking power budgets due to cost, longevity, or governmental regulations such as Energy Star™.

None of these requirements are easy to overcome in bulk silicon. In contrast, SOI offers Freescale designers the room, quite literally, to design in the peripherals required by our customers without growing the die size.

SOI not only provides a speed boost at the same voltage, it also ensures the data flowing across the device is correct by reducing soft errors.

And perhaps most importantly in today’s applications, SOI offers a greater improvement of transistor leakage than those made in bulk silicon. This affects the power dramatically.

The basic tradeoff with SOI is higher performance at the same power of bulk or same performance at a lower power. Freescale designers opt for the latter with nominal voltages of our PowerQUICC® III family of 1.1 to 1.0V. This minuscule nominal voltage increases our power saving even more by decreasing the dynamic power because of smaller voltage swings than what would be required of bulk for the same performance.

SOI offers another benefit over bulk in that latchup is not a concern. Because this concern exists in bulk, the p- and n- wells must be spaced further away than in SOI. Moreover, there must be structures between the p- and n- wells to help with the isolation. SOI gives us this isolation at a greatly smaller dimension, allowing all the structures to sit closer together.

In conclusion, the PowerQUICC III Family offers higher performance, higher integration, within a smaller power envelop due the benefits of SOI.