Band offset diagnostics of advanced dielectrics

Abstract

We present a non-contact electrical metrology of advanced dielectrics on silicon with an emphasis on monitoring the composition of mixed dielectrics such as oxynitrides and hafnium silicates. The approach takes advantage of significant band offset differences between individual components of the mixed dielectrics. To maximize the sensitivity to the band offset, the measurement is done in a tunneling range under the Self-adjusting steady state (SASS) condition. Such a condition is obtained when a corona charging pulse induces a tunneling current through the dielectric that matches the ionic charging current. Positive corona is used to probe the conduction band offset, while negative corona is used to probe the valence band offset. The key measured parameter is the dielectric voltage under the SASS condition. It is measured with a commercial corona–Kelvin tool, with macro-(mm²) and micro-(30 × 30 μm²) charging and monitoring capability. The dielectric surface potential is measured with a vibrating Kelvin-probe. Modeling of the tunneling current is used to illustrate the principle of the approach and to support the pertinent SASS equations. The method is applied to a skew of SiON mixed dielectrics on p-Si.