IBM is working with CMOS RF chip specialist Peregrine Semiconductor to bring its silicon-on-sapphire (SoS) devices into the 4G mobile phone market.
The fruits of a two-year joint development between the firms will see IBM manufacturing Peregrine’s UltraCMOS devices on a 180nm process on 200mm semiconductor wafers.
This is an important step for the RF CMOS technology, which is used in the wireless front-end circuits of mobile phones, 4G basestations and satellite systems.
The established semiconductor technologies for mobile radio circuits, such as amplifiers, switches and modulators, are gallium arsenide (GaAs) and more recently gallium nitride.
Replacing GaAs chips with CMOS in mobile phones is not a new phenomenon. As long ago as 2006 it was suggested that by now almost half of all RF circuits in mobile phones would be CMOS. This has not happened, but designers continue to explore alternatives to GaAs ICs.
As the high-frequency performance of CMOS started to match that of GaAs with process shrinks, suppliers started developing CMOS RF chips which they claimed could have cost, reliability and integration benefits over GaAs.
IBM’s SoS partnership with RF CMOS proponent Peregrine could be an important step in bringing the technology into the mainstream.
SoS is a variation of silicon-on-insulator (SOI) technology, which incorporates an ultra-thin layer of silicon on a highly insulating sapphire substrate. IBM is a leading player in the commercialisation of SOI process technology.
According to Jim Cable, president and CEO of Peregrine Semiconductor, the aim is to “deliver the promise of Moore’s Law for high-performance RF CMOS”.
Other companies interested in CMOS RF chips for mobile phones include Silicon Labs, Analog Devices and Texas Instruments.
Take one element of the front-ends circuits in a mobile phone, the RF switch. The options include GaAs switches, bulk-CMOS, MEMS and SoS devices.
For example, Analog Devices has its ADG9XX-family of 1GHz bulk-CMOS switches, which can be used use in the 900MHz ISM (industrial/scientific/medical) band.
For 3G’s 1.9GHz to 2.2GHz bands Peregrine has a CMOS device capable of switching between the two transmit channels in dual-band W-CDMA and GSM mobile phones.
Texas Instruments has an all-CMOS 2.4GHz ZigBee transceiver fabbed on its 180nm CMOS process.
Peregrine said it has sampled the first CMOS RF chips fabbed on IBM’s 180nm process to one customer and commercial production release is expected in 2011.