Stop, go, yield - Manufacturing

Electronic News, Nov 4, 2002 by Tom Murphy

The new mantra is yield.

It no longer matters who arrives at the 90nm process node first.

The migration to new process technologies maybe essential for the semiconductor industry's growth curve, but it's rife with pitfalls, pratfalls and snafus. As companies race to take advantage of smaller feature sizes, more transistors and the higher performance parameters of 130nm technology, they have been stopped in their tracks by such issues as high mask costs, low yields and stifling frustration associated with incorporating new materials.

The industry as a whole has struggled to ramp up 0.13-micron process technology, but there have been a number of manufacturing issues never encountered before that have resulted in low yields. And migration to 90nm technology promises to be even more challenging.

Some have suggested the industry call off the migration altogether and make sure all of the bugs are worked out at the 130nm generation first. But that would be like sticking your finger in the Hoover Dam after the floodgates have been opened wide. It's simply not realistic.

Two companies are dealing with yield issues head-on, and they are providing manufacturers with hope through technologies designed to ease the migration process.

Advanced Micro Devices Inc. (AMD) has developed a technology called Advanced Process Control (APC) that allows chipmakers to make fine adjustments to their tool sets while wafers go through the manufacturing process. AMD claims its homegrown technology is unmatched.

And San Jose-based PDF Solutions Inc. is marketing yield improvement methodology that can model both silicon process technology and a chip design, anticipate the problems that could show up and then suggest fixes to those problems even before mask sets are purchased.

By its own choosing, AMD is taking on the manufacturing prowess of Intel Corp. In doing so, AMD is locked in an ongoing struggle to reduce cost-per-die as rapidly as possible while maintaining relevance in microprocessor technology. AMID can't afford to throw away several batches of defective wafers because the fab tools used to produce them fell out of precision timing during the manufacturing process.

While AMID has long claimed that is has the lowest cost-per-die in the MPU business, the company also has the unenviable task of trying to keep up with Intel in process technology--even though Intel outspends AMD more than seven-fold in capital expenditures.

AMD's solution was to make its wafer processing tools smarter and more responsive than anything else in the industry, said Dick Deininger, process technology director at AMD.

"Our competitor dwarfs us in size and we had to keep our devices competitive. We had to do it rapidly in order to keep up and get a jump on them," Deininger said.

Tool vendors market their own process control solutions, but AMD developed a system that it claims further improves upon anything offered by the capital equipment vendors. AMID actually went outside the semiconductor industry to find ways to improve upon the processes in its fabrication facilities. As a result, AMD can fine-tune its instruments and tools beyond the stated specifications claimed by the tool manufacturers.

AMD's APC technology adds consistency to manufacturing processes, bringing them to the same level seen by the oil industry in the petroleum refining process, Deininger said. APC is a real-time, closed-loop automation process by which a string of 10 to 12 tools are linked together over a network and hooked up to a computer. The end-result: better products and improved efficiency.

The computer takes measurements on wafers in the middle of processing and can signal adjustments as they move through each step, Deininger said. "If some aspect of the wafer processing is slightly off, we make adjustments further down stream so wafers can be corrected," he added.

APC also makes adjustments to the machines where flaws were originally detected so that the next batch of wafers does not suffer from the same flaws, Deininger said.

The first AMD fab to benefit from the process was Fab 25 in Austin. AMD converted a logic fab to a flash memory factory in four months, thanks in no small part to APC. Critics had argued that AMID wouldn't be able to convert the fab at all.

AMD says half of the tools in its Dresden, Germany-based Fab 30, which produces all of AMD's MPUs, are equipped with APC.

Some other benefits AMD has noticed are reduced costs in wafer manufacturing and a smaller number of test wafers that have to run through all of the steps, Deininger said. APC also improves yields.

Competitors are quick to dismiss AMID's accomplishments andsay automation in fabs has been around for a few years. But from AMD's perspective, no one else has the technology because it was developed completely in-house. IBM Corp. and Texas Instrument Inc. have both implemented APC to a degree, Deininger said. In addition, AMID recently disclosed that it would help implement APC for United Microelectronics Corp. (UMC) of Taiwan at the companies' joint-venture foundry in Singapore. UMC benefits from a technology and capacity sharing agreement with AMD.