PURPOSE: To supply a high purity molecular beam by suppressing the high temperature of a PBN crucible to prevent an impurity gas from being exhausted from the graphite wall surface of a PBN crucible.
CONSTITUTION: A crucible 1 is made of pyrolytically decomposed boron nitride (PBN), and a radio frequency (RF) coil 4 is used for heating to pyrolytically decompose a material gas. A graphite wall 3 covered with SiC has thin edges to suppress the thermal conduction to the crucible 1. The wall 3 is heated by supplying a current to the coil 4, and the gas fed from a material gas inlet 2 and passed through a gas passage hole 8 is pyrolytically decomposed. Accordingly, the crucible 1 is heated only by the thermal conduction through the radiation heat of the wall 3 and the contact of the wall 3 with the crucible 1. Thus, the crucible 1 does not become high temperature, the exhaust of an impurity gas, such as carbon can be reduced, and high purity molecular beam can be supplied.
MARUNO SHIGEMITSU
OGATA HITOSHI
