ADVANCED HIGH-CURRENT ECR ION SOURCES FOR IMPLANTERS

We have already introduced a high-current ECR ion source producing a 200-mA beam of oxygen ions with an 80% O+ fraction. Two more advanced ECR sources with a high-current density of more than 100 mA/cm2 have been newly developed. One source provides high-current density without the accompanying damage to the microwave transmitting window found with the earlier source. This damage, which occurs when high-speed backstream electrons attack the window, limits source lifetime. By adopting a multiple microwave inlet configuration for the introduction of microwaves into the plasma chamber, the ECR condition can be satisfied and high-density plasma can be generated without an attack by backstream electrons. The other is a very compact source producing a high-current beam at a very low-power consumption. This is achieved by reducing the inner diameter of the plasma chamber to 5 cm diameter, which is smaller than the cutoff dimensions for propagation of the 2.45 GHz microwave. A high-plasma density of 1 x 10(13) cm-3 has been obtained at the low microwave power of 250 W.