Abstract: Methods are provided for making retrograde trench isolation structures with improved electrical insulation properties. One method comprises the steps of: forming a retrograde trench in a silicon substrate, and forming a layer of silicon oxide on the walls of the trench by thermal oxidation, such that the trench is sealed and a space is formed within the layer of silicon oxide. The space can contain a vacuum or any of a variety of gases depending upon conditions of the thermal oxidation step. Retrograde trench isolation structures containing a space are also provided.

Abstract: A method of improving the yield and performance of IC devices fabricated on a semiconductor wafer is disclosed. The method includes fabricating via plugs in via openings provided in an intermetal dielectric (IMD) layer on a wafer, subjecting the wafer to CMP to isolate the via plugs, immersing and soaking the wafer in deionized (DI) water, and drying the wafer using isopropyl alcohol, typically in a Marangoni-type dryer. The Marangoni IPA drying step prevents the formation of static electricity on the wafer, and thus, prevents the adherence of small charged particles to the wafer. As a result, the yield of IC devices fabricated on the wafer, as well as the performance of the devices, is enhanced.

Abstract: A method of forming a shallow trench isolation structure is described. A mask layer and a photoresist layer with an opening are formed on a substrate in sequence. The photoresist layer serves as an etching mask, and then a portion of the mask layer and a portion of the substrate are etched to form a trench in the substrate. A portion of the photoresist layer is removed, and the opening is in-situ widened. Then, a portion of the mask layer exposed by the widened opening is removed. In addition, a top corner of the trench is rounded after removing the portion of the mask layer. Finally, the trench is filled with an insulation material to form a shallow trench isolation structure.