ILOG optimization software solves problems unique to semiconductor manufacturing

Semiconductor manufacturing involves a series of painstaking processes that must be repeated numerous times—with exact precision—over a period of several weeks. Ensuring these processes are completed in time to fill customer orders is a major challenge—one that has even confounded developers of sophisticated production-scheduling applications.

“Most production scheduling software doesn't operate with the time precision you need with semiconductors,” says Anthony Yu, a VP in IBM's engineering and technology services group. When IBM discovered a system that did work with that level of precision, it was installed at IBM's East Fishkill, N.Y.-based plant, where chips are made for the hottest new video game consoles: the Microsoft Xbox, the Sony Playstation 3, and the Nintendo Wii.

This application—called Fab PowerOps—was developed by ILOG, which specializes in technology for optimizing production and supply chain processes. After implementing Fab PowerOps at the East Fishkill plant, IBM's production times dropped by 15 percent—quite an accomplishment for a semiconductor operation, says Yu.

In IBM's plant, Fab PowerOps runs in the photolithography and diffusion areas. Photolithography—in which the chip's pattern is created—involves repeatedly performing a series of chemical treatments on an initially flat substrate. The diffusion process, which modifies the chip's electrical properties, involves repeatedly baking layer upon layer of material at high heat.

“That's a hard thing to model and schedule,” says Thomas Dong, ILOG's director of product management and marketing. “You don't have this problem making cars or DVD players. You don't do the same thing again and again.”

The East Fishkill plant employs an automated material-handling system that can run continuously—even when unattended. But that didn't mean wafers were routed through production in the most efficient way. For instance, the material-handling system could not ensure that all production tools were kept busy at all times, or were always free of bottlenecks.

The need to ensure all processes are completed within a certain amount of time adds to the scheduling challenge. “You only have a certain amount of time to get from one process to the next, and that's a hard scheduling problem,” Yu says. “As we release wafers into the line we have to decide how they flow through the factory, how they're queued up, and which lots get priority. It's quite complex.”

Fab PowerOps creates production schedules for tools in the plant's fabrication process areas, zooming in to plan for each tool, and out to plan for a set of tools and schedule daily plant processing. With production cycles that last at least a month, daily and weekly schedules need to be forecast and adhered to.

“We don't just look at the one tool,” Dong says. “We look at what's happening in all the furnaces simultaneously. We look forward in time to everything that needs to happen within the next eight to 12 hours.”

IBM was so pleased with its results that it has decided to market Fab PowerOps in conjunction with is own View line of manufacturing execution systems.