SCIENCE & ENGINEERING NEWS
San Diego, CA — The semiconductor industry is racing to develop a tool that can pattern integrated circuits (ICs) with features almost half the size of what is in production today. But optical tools, which have been the mainstay of semiconductor manufacturing to date, are not up to the task of imaging the small dimensions that will be required. These dimensions must be smaller than 100 nanometers, or 100 billionths of a meter. By comparison, features on today’s ICs are an airy 180 billionths of a meter.
And there is no time to lose. The Semiconductor Industry Association, San Jose, Calif., predicts that ICs with 70-nm features will be in production by 2008.
Researchers at IBM are turning to electron beams for the job. These are not new to the industry. But because they paint in each small feature of each chip on the semiconductor wafer, they are too slow to be practical for manufacturing. Throughput, as it is called, is low.
IBM uses a variation on this approach, called projection e-beam systems. They improve throughput by shining an electron beam through a mask in order to image a larger segment of a wafer in one flash. But in order for these tools to find a place on the manufacturing floor, they must be faster yet.
Key advances by scientists at IBM Microelectronics in East Fishkill, N.Y. may finally bring projection e-beam up to speed. Two ways of improving speed are exposing more of the wafer in a single step, and increasing beam current so that less time is needed for each exposure. They have devised a set of magnetic lenses for the electron optics that shifts the magnetic axis as the beam is being scanned. The new lenses keep the electron beam from being distorted as it is scanned away from the center of the image, allowing a larger area to be projected onto the wafer at one time. And a new high-emittance electron gun produces a wide uniform beam that decreases the time needed to expose the wafer at each step. The magazine’s Web site is http://www.spectrum.ieee.org .