Characterization of the solubility, electrical behavior and stress state of undoped and boric oxide/phosphorus oxide-doped, as-deposited and annealed PECVD germanosilicate glasses

Present isolation technology in microelectronic applications uses chemical-mechanical polishing (CMP) in order to achieve planar surfaces for dielectric films used in trench isolation and inter-layer dielectric structures, among others. Reflowed glasses have not played an important role in planarization because of the high temperatures involved. The present research has led to the development of a new glass technology based on doped and undoped germanosilicates, which can be reflowed during thermal treatment as low as 550°C to form a planar surface. Plasma-Enhanced Chemical Vapor Deposition (PECVD) methods were developed that are capable of depositing boron and/or phosphorous doped and undoped germanosilicate films of any desired composition of SiO2 and GeO 2 at 200°C. Energy Dispersive Spectroscopy (EDS) and Auger Electron Spectroscopy (AES) were used to determine film composition.;Undoped germanosilicate films could also be planarized at relatively low temperatures in inert gas atmospheres. For example, such films could be planarized over 1/2mum trenches in argon after a 1 hour anneal at 850°C, or a 6 hour anneal at 750°C. Doped films of defined compositions in the quasi-quaternary system GeO2-SiO2-P2O 5-B2O3 can be planarized over severe topography following anneals in argon at 600°C for 1 hour or at 550°C for 12 hours. Steam annealing, while enhancing reflow significantly, also removes germanium dioxide from the film, thereby raising the reflow temperature of the resultant glass. This removal suggests a reflow temperature hierarchy in which a germanosilicate glass is deposited and subsequently annealed in either a single-step or two-step process to planarize the glass and raise its reflow temperature. Additional layers could then be deposited, and another germanosilicate could be added and treated with an identical anneal process, forming a new, planar surface without disturbing the structure of the underlying, previously annealed germanosilicate layers. The same novel anneal process has also been shown to produce germanosilicate glasses with good dielectric properties, low measured interfacial stress, and low water solubility. The germanosilicate technology could provide either a planarization alternative or a complimentary process to CMP in trench filling and inter-layer dielectric applications.