by Richard Halstead
Empire Magnetics, Inc.

In addition to highly repetitive tasks, positioning equipment has long been used to provide very specialized functions and processes.

A good example is the semiconductor manufacturing industry. According to a recent press report, at least forty new wafer fabrication plants are presently in the planning stages or actually being built. Since each plant represents a $2 billion to $6 billion investment, it is easy to estimate that there is some $200 billion going into this market in the next 3-5 years. And, since the process equipment represents the bulk of the investment, this is an important market for manufacturers of positioning and automation equipment.

In semiconductor manufacturing, the immediate presence of operators has always been an unacceptable source of contamination. The newer facilities are getting cleaner by completely removing people from the process; engineers are also changing the equipment designs to eliminate that source of contamination.

Initially, attempts by semiconductor manufacturing companies to get wafer fabrication processes under control were aimed at moving the process into an environmentally-controlled "clean room." By filtering the air, and carefully controlling the materials allowed into the clean room, the amount of particulation was reduced. By 1970, a Class 1000 clean room was considered quite good.

However, some of the equipment -- and operators moving around in "bunny suits" --still created a large number of particles. To avoid this problem, it was necessary to build even cleaner areas inside the clean room. This was done with laminar flow hoods and other devices, in an attempt to reduce the number of particles that can come into contact with the silicon wafers. In 1973-1975, Class 100 areas within the clean room were considered good.

About this time, the equipment in the area was carefully redesigned, removed and/or replaced, again minimizing the number of particles generated by the equipment. Equipment itself also began to be approved for clean room uses. The overall construction of a clean room, and all of its contents, became the focal point. By 1979, clean rooms rated at class 100, and which contained hoods with class 10 ratings, were becoming the standards of excellence.

Since the classifications are based on the number of particles floating around in a cubic volume of air, it became more and more difficult to remove the last few particles contained in the air. The obvious answer was to remove the air from the system.

Therefore, in the 1980s, equipment manufacturers began moving their semiconductor manufacturing processes into vacuum chambers. While the vacuum environment may be a part of specific processes, it also has the advantage of not supporting particle motion.

Newer facilities move the wafers in and out of super-clean containment devices, as they are transported from one process to the next. Often this is a series of vacuum chambers, with transport systems in between. However, the chemical processes are still controlled by humans working in the process areas.

It is likely that the future trend will be to make large sections of the process line, or even the entire process line, operate in a vacuum. The system will essentially be a long pipeline with many segments that can be sealed off from one another. Once the wafers have moved into a segment or section, that section is sealed, the appropriate process is accomplished and the wafers are then transported to the next section.

By having large numbers of processes linked into a series of vacuum chambers, several advantages are gained. The lack of air in the system prevents transport of contaminating particles, and the time spent pumping down the process chambers to the required levels of vacuum can be eliminated. The process becomes more of a continuous flow, as opposed to a batch mode.

The leading-edge technologies in semiconductor manufacturing are spin-offs of development work that was originally done to create the "beam lines" found at National Laboratories. The long vacuum chambers and equipment used to make these beam lines are patterns that will lead system designers to the long vacuum systems that will probably be the wafer fabrication lines of the future.

In these beam lines and in the wafer fabrication process, it is necessary to have equipment that is fully automated and very precise. It must also operate in a vacuum and not generate hydrocarbons or make particles. There are few suppliers of such equipment, and few pieces of general use equipment fill all of these requirements. Our firm, Empire Magnetics, Inc. is a supplier of high precision vacuum-rated motors and Class 10 motors rated for clean room use.

In a joint effort with Lawrence Berkeley National Laboratories, Empire Magnetics is developing new motors that are suitable for use in vacuum and space applications. Through these and other efforts, the National Labs are assisting U.S. manufacturers in applying new technologies, with the goal of maintaining a competitive edge in the worldwide market.

This article first appeared in MOTION, published by Motion Corporation, P.O. Box 21730, Carson City, NV 89721-1730.