Pushing silicon-germanium (SiGe) technology to new levels of switching speed, IBM Microelectronics has unwrapped building block devices that operate at 110 GHz using its fourth-generation SiGe process. Dubbed the SiGe 8HP, this 0.18-µm process will be available to top-tier communications equipment makers. Commercial chips are expected later this year.
The circuits were built with SiGe heterojunction bipolar transistors (HBTs) with an fMAX of 285 GHz. The recorded delay time of the ring oscillator (see the figure) is 4.23 ps, translating to a 110-GHz switching. Each oscillator stage's supply current is about 2 mA at 3.6 V. Copper interconnects are used for speed and lower losses. The design has 50-Ω aluminum transmission lines.
"On top of copper interconnects, we built a thick (4-µm) aluminum layer for transmission lines," said Seshadri Subbanna, senior engineering manager with IBM Microelectronics' Advanced Communications Technology Development.
IBM is releasing complete design tool kits for its SiGe biCMOS 5PA and 5DM processes. The 5PA suits GSM cellular handset power amplifiers. The 5DM has passive elements needed in wireless communication devices.
Copper interconnects used in the 5DM process have enabled the development of a 3.580- to 3.980-GHz voltage-controlled oscillator (VCO) for GSM/DCS/PCS applications. This monolithic chip with integrated passives can replace up to 30 discretes in hybrid VCO modules. It can be housed in miniature packages that require a footprint that's 85% smaller.
The SiGe 8HP was unveiled at February's Gorham Compound Semiconductor Outlook Conference in San Mateo, Calif., where IBM demonstrated ring oscillators and other building blocks. For details, go to www.ibm.com.