A selective SiO2 film-formation technology using liquid-phase deposition (LPD) around room temperature for fully planarized multilevel interconneetions is developed. The LPD technique utilizes supersaturated hydrofluosilicie acid (H2SiF6) aqueous solution as a source liquid. The LPD-SiO2 films can be selectively formed on chemical vapor deposition (CVD) SiO2 underlayers in the trenches "between photoresist patterns or tungsten wiring with photoresist as mask. For polysilicon patterns with photoresist masks, the LPD-SiO= films creep along the polysilicon and photoresist sidewalls. The selective deposition mechanism can be explained as siloxane oligomers, which are formed in the supersaturated H2SiF~ aqueous solution, have different chemical reactivity between the photoresist and substrate surface. Global planarization of trenches between tungsten wiring is achieved using the selective LPD-SiO2 deposition technique. A fully planarized double-level tungsten interconnection is realized using both selective LPD-SiO2 film deposition and selective tungsten CVD via filling. Low contact resistance of ca. 0.3 ~I/unit is achieved for via holes 0.8 p~m in diam.
Gate electrode etching using a transformer coupled plasma (TCP) was studied for future device fabrication. The influence of chamber hardware configuration on plasma characteristics and etching performance has been studied for polysilicon and polycide etching. It has been found that etching and plasma uniformities greatly depend upon dielectric plate shape and position of the inductive coil on the dielectric plate, and that distance between the inductive coil and the dielectric plate has a big impact on the etching performance. This impact on the etching performance is caused by changing the capacitively coupled component in the inductively coupled plasma.
A new interlayer dielectric film formation technology for multilevel interconnection by catalytic chemical vapor deposition has been developed. This technique utilizes fluorotriethoxysilane [FSi(OC2Hs)3] and water vapor as gas source. The films deposited at 25~ have remarkably good properties, such as tightly.bonded Si-O networks with no OH radicals, large density value (2.20 g/cm3), small residual stress (50 MPa), low leakage current, and small dielectric constant (3.7), although the film contains residual fluorine and carbon atoms with 5.3 • 102' and 2 • 102' atom/cm 3, respectively. Based on the film characterization results, we speculate that the reaction sequence for the film deposition is: hydrolysis of fluorotriethoxysilane monomers, formation of siloxane oligomers with reaction by-product (alcohol), adsorption of the oligomers to the wafer surface, and then polymerization. The electrical conduction mechanism study revealed that the Schottky emission was dominant for the electric conduction through the film. It also has clarified that the deposition film thickness has no dependence on A1 wiring widths, and is completely isotropic with no crack or keyhole in the film.
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