Spin-on films add new dimension to ULSI circuits

Spin-on oxide films, natural candidates for improving interlevel dielectric planarization in ULSI circuits, are reviewed. The spin-on process, one in which a thin film is produced by spin-casting a liquid on a rotating wafer, is described. Spin-on films combine the planarization capabilities of a fluid with the dielectric properties of an oxide. They fill all the lower regions over the wafer and produce a planar top layer. Spin-on insulators can be used in combination with chemically-vapor-deposited (CVD) materials, and can also be combined with an etchback step to improve planarization. As a result, the depths of vias in the etching process can be made more uniform, and voids in the filling of via-contacts, which become a significant problem as the via size shrinks, can be eliminated.<>