Off-resonance microwave ion source for high-current molecular ion-beams

As the integration of semiconductor devices proceeds, each device size shrinks, resulting in requiring shallower p-n junction depth. Thus, molecular ion BF2+ is often utilized in place of the atomic ion B+for p-region formation. Microwave ion source is tuned to provide very high-current beams of such molecular ions. In this study we vary the source-magnetic field for a wide range from less than a tenth of the electron cyclotron resonance (ECR) magnetic field (87.5 mT for 2.45 GHz) to 1.3 times the ECR field. The result shows that the highest current for BF2+ ions is obtained at the magnetic field of 10 mT, although the highest B+ current is obtained at over the ECR field. The plasma generated at this condition is considered to be of low electron temperature and high electron density. The ion source is mounted on a commercial implanter beam line. The BF2+ ion current from the off-resonance microwave source is resultantly more than twice that of conventional Bernas source.