ELECTRICAL CHARACTERISTICS OF ULTRA-FINE TRENCH ISOLATION FABRICATED BY A NEW 2-STEP FILLING PROCESS

An ultra-fine trench isolation with superior electrical properties was formed using a new fabrication process. A void-free shape and suffici ent thickness of the field oxide were realized by two-step filling usi ng tetraethyl-orthosilicate (TEOS) oxide as the lower layer and high-d ensity CVD-SiO2 as the upper capping layer. The breakdown voltages wer e as high as 7.7 V, even for an isolation space as narrow as 0.13 mu m . The subthreshold characteristics of the metal oxide semiconductor fi eld effect transistor (MOSFET) isolated by the trench were kink-free. The threshold voltage of the parasitic MOSFET, furthermore, was more t han 6V, even without a channel stop implant to suppress punch-through.