The Reverse Engineer's View

RF/Mixed-Signal
In the big-dollar volume wireless communications market, a prime driver for reduced prices has been the integration of as many functions as possible into CMOS. In the frequency range from 1 to 10 GHz, one function that has resisted integration is the front-end amplifier of wireless receivers. Known as the RF amplifier or low-noise amplifier (LNA), it operates at the RF carrier frequency.

Most LNAs have been completed with silicon bipolar silicon-germanium (SiGe) transistors or Group III-V semiconductor materials such as gallium arsenide (GaAs). Compared to standard CMOS, neither SiGe nor GaAs can be regarded as high-volume, low-cost semiconductor process technologies. Therefore, integration of the LNA function onto a CMOS receiver die would remove both a cost component and a separate IC package from the system. The frequency range of interest here, roughly 1 to 10 GHz, contains such existing and future huge volume markets as IEEE 802.11 applications, WiMAX, W-USB (wireless universal serial bus), and GPS in cellular phones.

In approximate terms, the advancement of process technology from 90 to 65 nm can be expected to improve the basic unity-gain frequency response ( f_t ) of NMOS transistors from around 100 to 130 GHz. Many RF designs require a transistor f_t of at least 10 times the application frequency. So the technology migration from 90 to 65 nm will give CMOS circuitry significant added speed capability in the commercially important frequency range of 1 to 10 GHz.

Traditionally RF/mixed-signal processes have lagged behind the leading-edge logic processes. But the cost savings to be gained by integrating the RF front end of a cell phone into CMOS may drive these products into 65 nm quicker than expected. Wireless USB, as another applications area, operates from 3.1 to 10.6 GHz, right in the range enabled by 65-nm technology. Add in the advantage of low overall power consumption, and we have powerful drivers to accelerate the technology shift.

As an example, TSMC expects its 65-nm process to double standard-cell gates, increase speed by 50%, and reduce standby power by 20%. Broadcom, Qualcomm, and Freescale all have run early silicon through TSMC's initial 65-nm Cybershuttle, and Texas Instruments claims it has shipped 65-nm wireless sample products. While we would not expect to see 65-nm RF chips downstream in early 2006, given the cost drivers, we could see some by the end of the year.

Summary
Even though 65-nm logic product launches may dominate the media, there will be plenty of interest in the other segments of the industry. One thing is for sure?2006 will be interesting inside technology!

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