Sara Barron "Sputtering of high-performance dielectric thin films"
As new semiconductor systems are developed and implemented in niche or mainstream applications, the need for new dielectric materials becomes prevalent. Sputter deposition affords a straightforward approach to preparing candidate materials for thin film dielectrics. I have studied a number of thin film dielectric oxides. We choose to evaluate their properties in MIM capacitors, with noble metal electrodes to allow evaluation of the material properties without consideration of the chemical interaction with a semiconductor (Si, e.g.).
We find that a complex amorphous dielectric oxide of Zr0.2Sn0.2Ti0.6O2 has a dielectric constant of ~55, but only if deposited at substrate temperatures of 150 to 280 įC; at higher and lower temperatures, the dielectric constant falls to ~30 due to crystallization and low density, respectively.
A dysprosium-substituted titania is prepared by reactive RF sputter deposition with a dielectric constant~24, low leakage current, and low dispersion up to 1 MHz. We are integrating this material into silicon transistors.
Finally, we are developing a methodology to co-sputter dielectric oxides in a composition gradient. When deposited from an oblique sputtering source, such as that used in composition spreads, dielectric thin films exhibit an abnormal low frequency polarization that masks the intrinsic dielectric properties. We implement a negative electrical bias (~-70 V) to the substrate, which eliminates the void-mediated polarization and recovers the intrinsic properties of the dielectric.