Kenji Yasumura

Electrical Characteristics of Ultra-Fine Trench Isolation Fabricated by a New Two-Step Filling Process

An ultra-fine trench isolation with superior electrical properties was formed using a new fabrication process. A void-free shape and sufficient thickness of the field oxide were realized by two-step filling using tetraethyl-ortho-silicate (TEOS) oxide as the lower layer and high-density CVD-SiO2 as the upper capping layer. The breakdown voltages were as high as 7.7 V, even for an isolation space as narrow as 0.13 µm. The subthreshold characteristics of the metal oxide semiconductor field effect transistor (MOSFET) isolated by the trench were kink-free. The threshold voltage of the parasitic MOSFET, furthermore, was more than 6 V, even without a channel stop implant to suppress punch-through.