PolarFab recasts itself as pure-play BiCMOS foundry

PolarFab now has an ability to start more than 10,000 wafers per month. Monthly capacity will increase to 17,000 or more wafer by the beginning of next year, and to 22,000 by the beginning of the second quarter of 2001. At those rates, the plant can crank through 30,000 six-inch wafers (with 20+ masking steps) a quarter today, 35,000 in the first quarter of next year and 40,000 in the second quarter. "We have 170,000 square feet — we can expand capacity as needed," Peterson said.

PolarFab was formed following the acquisition of VTC by Lucent Technologies. VTC was a 1990 spinout of Control Data Corp., and had quickly distinguished itself as a supplier of disk-drive ICs, especially preamps and read channels requiring the additional noise immunity provided by a bipolar front end. VTC's customers i ncluded drive makers Seagate, Western Digital, Maxtor and Samsung, as well as chip suppliers like Cirrus Logic and Lucent Technologies.

"Ridiculous pricing pressures" in the disk drive industry, however, seemed to favor IC manufacturers who could 'bundle' preamps and read channels along with controllers and head positioners, said Peterson. "VTC could compete in the head preamp business when pricing was 'reasonable' — and when customer expectations were 'reasonable,' " Peterson said. Current conditions in the disk-drive IC business suggested that a pure-play foundry would be a better way to preserve margins on BiCMOS manufacturing, he said.

Lucent had purchased the intellectual property of VTC during the summer of 1999, and acquired 232 of the company's design and product engineers at that time. The remaining 420 employees now with PolarFab provide a number of "hand-holding" services to designers, in addition to manufacturing assistance. These include prototype assembly, wafer probe and final p ackage tests. In addition to yield enhancement, for example, PolarFab has dedicated teams exploring and preventing electrostatic-discharge and latch-up issues.

Beyond the pure-play model

These services go beyond what is ordinarily available for pure-play foundries or semiconductor makers selling excess capacity, Peterson said, and are intended to shorten what he calls the "time-to-volume."

The BiCMOS process, which implants bipolar transistors on a CMOS substrate, is especially useful for what Peterson calls "Big A, Small D" mixed-signal circuits, with ample analog content and some digital content. Bipolar transistors provide an extra measure of speed and noise immunity. While disk-drive read channels are increasingly fabricated in what Peterson calls "tweaked CMOS," the BiCMOS process remains a favorite for communications interfaces and other chips requiring analog precision on their front ends.

In addition to a 0.5-micron BiCMOS process, PolarFab maintains a complementary bipola r capability that is useful for high-speed communications circuits. The NPN transistors have 6- and 7-GHz f_T's and the vertical PNPs have a 1.5-GHz f_T.

A silicon germanium (SiGe) bipolar capability currently in development will offer NPN transistors with 30-GHz f_T's. The supporting CMOS structure, "Polar 35," will reflect a 0.35-micron geometry.

A 16- and 30-V lateral DMOS (LDMOS) transistor capability already in place will build spindle motor drivers for the disk drive industry. A 100-V version, now coming out of development, will support wireless infrastructure applications such as cellular basestation transmitters.

In addition to foundry services, PolarFab is working with third-party vendors to build a CMOS standard-cell library. The analog and mixed-signal intellectual property it hopes to provide include bandgap references, op amps, D/A and A/D converters, RC filters, and non-volatile EPROM and EEPROM for trimming.