Lely method

The Lely method, also known as the Lely process or Lely technique, is a crystal growth technology used for producing silicon carbide crystals for the semiconductor industry. The patent for this method was filed in the Netherlands in 1954 and in the United States in 1955 by Jan Anthony Lely of Philips Electronics.^[1] The patent was subsequently granted on 30 September 1958, then was refined by D. R. Hamilton et al. in 1960, and by V. P. Novikov and V. I. Ionov in 1968.^[2]

A diagram of the modified Lely method, showing a graphite crucible surrounded by induction coils for heating. Silicon carbide charge is sublimated from the bottom of the chamber and deposited on the upper lid, which is cooler.

Overview

The Lely method produces bulk silicon carbide crystals through the process of sublimation. Silicon carbide powder is loaded into a graphite crucible, which is purged with argon gas and heated to approximately 2,500 °C (4,530 °F). The silicon carbide near the outer walls of the crucible sublimes and is deposited on a graphite rod near the center of the crucible, which is at a lower temperature.^[2]

Several modified versions of the Lely process exist, most commonly the silicon carbide is heated from the bottom end rather than the walls of the crucible, and deposited on the lid. Other modifications include varying the temperature, temperature gradient, argon pressure, and geometry of the system. Typically, an induction furnace is used to achieve the required temperatures of 1,800–2,600 °C (3,270–4,710 °F).^[2]: 195

See also

• Acheson process
• Czochralski method
• Sublimation sandwich method

References

1. US 2854364, Lely, Jan Anthony, "Sublimation process for manufacturing silicon carbide crystals", published 1958-09-30, assigned to North American Philips Co., Inc.
2. Byrappa, Kullaiah; Ohachi, Tadashi (2003). Crystal Growth Technology. Springer Science & Business Media. ISBN 9783540003670. Retrieved 10 September 2018.