Lely method

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.

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

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.

Several modified versions of the Lely method 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).

See also

• Acheson process
• Czochralski process
• Sublimation sandwich method