Electrical Reliability of Solgel Barium Titanate Films on Copper Foils for Organic Package Integration

There is an increasing need for integrating high dielectric constant ceramic thin film components in organic and 3D IC packages to lower the power-supply impedance at high frequencies and supply noise-free power to the ICs. Sol-gel approach is very attractive for high density capacitors because of its ability to precisely control the composition of the films and the ease of introducing dopants to engineer the dielectric properties such as breakdown voltages and DC leakage characteristics. Thin films on copper foils lend themselves to organic package integration with standard foil lamination techniques used in package build-up processes. However, fabrication of thin film barium titanate on copper foils is generally affected by process incompatibility during crystallization in reducing atmospheres, leading to poor crystallization, oxygen vacancies and copper diffusion through the film that degrades the electrical properties.This paper focuses on the dielectric properties and electrical reliability of thin films on copper foils. Thin film (300-400 nm) embedded capacitors with capacitance density of 2 μF/cm2, low leakage current and high breakdown voltage were fabricated via sol-gel technology and foil lamination. To lower the leakage current, the chemical composition was altered by incorporating – 1.) Excess barium 2.) Acceptor dopants such as Mn. Both approaches lowered the leakage current compared to that of pure barium titanate. SEM analysis showed enhanced densification and refined grain structure with chemistry modification. The films showed good stability in leakage currents at 150 C with an applied field strength of 100 kV/cm, demonstrating the electrical reliability of these films.