Oligomeric Ketoester Precursors for Improved Polyimide Planarization and Gapfilling
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
The ability to cover irregular topography with a flat (nonconformal) coating is limited by the viscosity and wettability of the polymer solution. That is, the surface tension of the solution must be sufficiently low so as to spontaneously wet the surface to which it is applied and, at a given temperature, the solvent, percent solute (solids), and molecular weight (MW) of the solute polymer must permit a viscosity low enough for flow. Both planarization and gapfilling require flowable polymer solution viscosity at relatively high solids concentrations. In polyamic acid solutions, this involves good flow of nearly solventless polymers near the solidification (cure) temperature. However, high solids content and low viscosity are competing parameters: an increase in solids content leads to higher viscosity.