Control software seen as 300-mm production hurdle
By David Lammers
EE Times
(07/14/00, 01:02:39 PM EDT)
SAN FRANCISCO ( ChipWire) -- The 300-mm transition appears to be upon the chip industry at last, as Semicon West attested this past week. With a full line of 300-mm wafer production equipment ready from Applied Materials Corp. and others, and with commercial 12-inch fabs under construction by companies including Infineon, Intel, Taiwan Semiconductor Manufacturing and Texas Instruments, the focus is shifting to how to link the tools in a way that will deliver the cost efficiencies promised by the larger wafer size.
That challenge -- creating the control software needed for fully automated operation of $2 billion to $3 billion fab lines -- is among the most formidable industrial control efforts ever attempted. It is the chip industry's equivalent of the Apollo missions to the moon.
With better yields as the ultimate goal, advanced process control requires more intelligent equipment and fab control systems that keep track of each tool, lot and wafer. Participants at Semicon West openly worried that the gains offered by the larger wafers may be lost unless better control systems are developed at all levels.
"From the perspective of cost of ownership, the tool reliability is probably OK. But for the control systems, none of the vendors today can offer the level of complexity required for a 300-mm facility," said Horia Grecu, deputy general manager of a 300-mm pilot line in Dresden, Germany, operated by Motorola Inc. and Infineon Technologies AG.
Much of the work to date over the long road to the 300-mm wafer generation has been spent on developing the equipment. At Semicon West, Applied Materials senior vice president Sass Somekh said the company has developed 21 production tools capable of 300-mm wafer processing and expects to ship 175 production tools by year end.
"For five years, the transition to 300 mm has been on and off, on and off. Now it is really happening," Somekh said.
Grecu of the Motorola/Infineon pilot line said work still needs to be done in two key equipment areas: lithography and chemical mechanical polishing (CMP). "The data we have been collecting in Dresden shows that the equipment set for 300-mm production is not ready yet, but according to our criteria, it will be ready by the end of the year," he said.
The line in Dresden now processes about 1,800 300-mm wafers per month of 64-Mbit DRAMs, giving the partners a rich base of knowledge. Each tool category has been statistically measured, charted and scored. A 70% readiness rating is enough to provide a 30% cost gain, on a given square inch of silicon, compared with 200-mm wafers.
"In November 1999, scores were averaging 28%. As of right now, we are at a 60% average, and I suspect that by the end of the year the average score will be at 70, at a point where we can start a fab but still need to keep a watch on the tools," Grecu said.
Motorola has not announced a 300-mm fab, but Grecu said he is confident the company will divulge its plans, possibly with a partner, in time to begin construction next year. Infineon partnered on its facility with German fab-engineering firm Meissner & Wurst; Motorola may work with a similar partner, Grecu said.
Exceeding limits
Industry veterans at Semicon West said much of the work done at pilot lines and R&D centers has concentrated on developing 130-nm (0.13-micron) process technologies and individual pieces of equipment to work on the 300-mm wafers, which are 2.5 times larger in surface area than their 200-mm predecessors. A cassette of twenty-five 300-mm wafers, at about 18-19 pounds, exceeds the weight limit for repetitive human handling set by the Occupational Safety and Health Administration. Ideally, the cassettes -- called FOUPs, for front-opening unified PODs -- would be moved from tool to tool by automated material-handling systems, although human-guided carts can be used in cases wherefully automated systems are still under development.
Bringing the FOUP into the tool automatically involves another layer of control. And once the wafer is inside and the process step goes forward, the process recipe for that particular wafer should be loaded automatically.
Reducing human error in "dialing in" the process recipe is increasingly important because a single wafer may hold many thousands of dice. "One wafer can be worth about as much as a Mercedes, and if an operator makes a mistake on a cassette, it can cost nearly as much as that person's lifetime wages," said Charles Baylis, a factory automation software guru at DomainLogix, based in Austin, Tex.
Besides reducing human handling (and goofs), automated systems will let chip makers automatically adjust their processes. A CMP tool, for example, must include feedback loops to adjust for wear and tear on the grinding pads, the condition of the slurry and so on. That in turn has led to more single-wafer (rather than batch) processing. And Applied Materials and others are offering in situ metrology and inspection modules that provide real-time information to the tool to which they are attached.
"For many 200-mm fabs, automation was shoehorned in. For 300-mm fabs, the industry has developed a whole set of standards -- the Global Joint Guidelines -- but we are still having a lot of problems getting them implemented and refined," said Peter Cross, a senior software engineer at Intel's Chandler, Ariz., facility who co-wrote several of the standards developed over the past few years by Semiconductor Equipment and Materials International. "We are crossing our fingers and working with our suppliers."
Besides the various standards that deal with how the 300-mm wafers are brought into the tool and moved around the factory, Cross said, Intel is asking its equipment suppliers to support SEMI's E30 and E94 communications standards, which enable advanced process control for specific wafers in a lot.
For the equipment purchase orders from Intel to its suppliers, Intel expects adherence to the advanced process control (APC) standard by the second quarter of next year, and it's targeting year's end for adherence to the material handling standards. Intel's aggressive schedule calls for the company to bring up a large pilot facility, called D1C, in Portland, Ore., that would provide learning for even larger 300-mm facilities in Arizona and New Mexico.
Faster to the floor
Besides achieving more advanced control over work in progress as wafers move through the fab and more precise process control within the tool, Intel wants to get equipment up and running faster -- a version of plug-and-play at the factory floor. "We need to [halve] the time from when the tool hits the dock to when it's fully running," Cross said. And that requires better fab control software.
Controlling a few tools in a small pilot line, where much of the attention is on perfecting new processes on the larger wafers, is a far cry from keeping a large fab running 24 hours a day. And while the SEMI factory control and communications standards are comprehensive, standards can only go so far. Keeping the interface standards somewhat loose means that the individual IC manufacturers and their suppliers must work out the details of automated manufacturing systems in the "real world" of the factory floor.
The road map for factory control systems that Dresden pilot line manager Grecu took to Semicon West was peppered with yellow and red dots, indicating areas for which solutions are either not yet ready or not available at all.
"Some things are not in place yet. For example, if a FOUP has 25 wafers and you want to include multiple process lots in each FOUP, you can't do that today. That is important because with these large wafers, and the smaller dice from the advanced processes, 25 wafers may be more than the entire order calls for," Grecu said.
Small wafer lots are especially important to the foundries and somewhat less so to companies that may be planning to run DRAMs or microprocessors in large volumes through their 300-mm fabs.
Brent Brook-Allred, general manager of the factory management division at PRI Automation Inc. in Billerica, Mass., is on the front lines of the 300-mm factory automation battle. Brook-Allred's software development group in Toronto is working on a new generation of factory management software, based on Windows NT and object-oriented software techniques.
PRI, along with Brooks Automation and Applied Material's Consilium division, is a leading supplier of automation systems and software to the semiconductor industry. With about 300 programmers among its 1,500 employees, PRI has come up against the industry-wide shortage of software engineers as it works to address the issues of 300-mm automation. "We not only recruit in the United States, but have about 125 software engineers in Toronto," Brook-Allred said. "But no doubt about it, the shortage of human capital is a huge challenge, and that is true for both Asian and North American companies."
Will the fab control issues be worked out in time for the early adopters of 300-mm wafers? "We are not at 80% [of the overall software solution], but we are not at 20 percent either," Brook-Allred said. "It is a risk-reward situation.
"Many people in the semiconductor industry are reluctant to change, and we have to bring these ultraconservative people to the point where they have the confidence level needed to be successful early adopters" of 300-mm factory automation systems. |
