ION SOURCE

PROBLEM TO BE SOLVED: To provide an ion source which produces divalent boron ions, B , in large amounts at a higher density by bonding a boron-containing plate near the exit of an ion source chamber and to a part of another interior wall to perform a plasma sputtering. SOLUTION: An arc chamber 1 for an ion source is a bottomed container with an upper plate 2 secured to its opening, the chamber 1 and the upper plate 2 together forming a closed space that is evacuated. In the center of the upper plate 2 is an opening for taking out a beam, i.e., a slit 3. A U-shaped filament 5 is attached to the wall surface of one side of the container, and a filament current is introduced from the outside by means of a current introducing terminal 9. A reflecting electrode (reflector) 6 is secured to the wall surface opposite to the filament 5. A BN plate 8 is bonded near the slit 3 in the upper plate 2. By providing the BN plate 8, larger amounts of divalent boron ion beams can be produced.