Isolation on Si wafers by MeV proton bombardment for RF integrated circuits

This paper studies issues related with using high energy protons to create local semi-insulating silicon regions on IC wafers for device isolation and realization of high-Q IC inductors. Topics on two approaches, i.e., one using Al as the radiation mask and the other using proton direct-write on wafers were studied. It was shown that Al can effectively mask the proton bombardment of 15 MeV up to the fluence of 10/sup 17/ cm/sup -2/. For the unmasking direct write of the proton bombardment, isolation in the silicon wafer can be achieved without damaging active devices if the proton fluence is kept below 1/spl times/10/sup 14/ cm/sup -2/ with the substrate resistivity level chosen at 140 /spl Omega/-cm, or kept at 1/spl times/10/sup 15/ cm/sup -2/ with the substrate resistivity level chosen at 15 /spl Omega/-cm. Under the above approaches, the 1 h-200/spl deg/C thermal treatment, which is necessary for device final packaging, still gives enough high resistivity for the semi-insulating regions while recovering somewhat the active device characteristics. For the integrated passive inductor fabricated on the surface of the silicon wafer, the proton radiation improves its Q value.