MEMC Announces Advanced Wafer Innovation; Provides Customers with Higher Yields.

St. Peters, Mo.--(BUSINESS WIRE)--Sept. 2, 1999--

MEMC Electronic Materials, Inc. (NYSE:WFR) today announced the development of an advanced silicon wafer innovation for use in microelectronic applications. Wafers with this new feature, called Magic Denuded Zone(TM) (MDZ(TM)), produce internal gettering action during device processing far more reliably than has been achieved to date. This provides greater long-term manufacturing yield stability for customers. The principle behind the technique relies on patented technologies developed by MEMC that effectively and accurately control the distribution of crystal lattice vacancies in the wafers. The MDZ(TM) process can be applied to any polished silicon wafer and to P/P- epitaxial wafers to provide a well-defined and predictable level of internal gettering and denuded zone depth during integrated circuit fabrication.

For the past 18 months both 150mm and 200mm MDZ(TM) treated wafers have been evaluated in some of the most advanced fabrication lines of MEMC's customers with tremendous success. The positive reaction by customers is due to higher yields with this material. MDZ(TM) treated wafers also provide two other major device- manufacturing advantages: MDZ(TM) provides reliable internal gettering at lower thermal budgets, and it allows the elimination of several costly steps at the beginning of the device manufacturing process.

The behavior of oxygen in conventional silicon wafers is complex and has many sources of variation. For the past 20 years, the silicon and device industries have struggled to control this behavior with varying degrees of success. Conventional silicon wafers require additional treatments customized to the specific crystal process and device processing sequence. The Magic Denuded Zone(TM) process pre-programs the wafer to provide both a controlled denuded zone depth and density of oxygen precipitates in essentially any device processing sequence with no extra intervention required by the device manufacturer. "MDZ(TM) wafers do not need to be carefully tailored to a specific application, eliminating complexity in the silicon wafer business," commented Dr. Robert J. Falster, Director, Silicon Materials Research, MEMC. "MDZ(TM) wafers robustly produce distributions of oxygen precipitates with controlled densities and denuded zone depths in essentially any application."

Patents for MDZ(TM) have been applied for in all major countries. The U.S. application has already been allowed and will issue in the near future. Patent applications are also on file in Europe, Japan, South Korea, Taiwan, China, Singapore, and Malaysia. The international application published as WO 98/38675 on September 3, 1998.

Additional information on MDZ(TM) treated products is available at MEMC's web site at www.memc.com.

MEMC is a leading global producer of silicon wafers. The silicon wafer is the fundamental building block of semiconductors, which, in turn, are found in every type of microelectronics application, including computer systems, telecommunications equipment, automobiles, consumer electronics products, industrial automation and control systems. Headquartered in St. Peters, MO, MEMC operates manufacturing facilities directly or through joint ventures in Italy, Japan, Malaysia, South Korea, Taiwan and the United States.