Thin film processing and integration methods to enable affordable mobile communications systems

Utilizing a co-planar device design we have successfully designed, fabricated, characterized, and optimized a high performance Ta2O5 thin film passive buffer layer on Si substrates, which will allow the integration of Ba1-xSrxTiO3 (BST) films with large area affordable Si substrates. This passive buffer layer thin film was fabricated via the industry standard metalorganic solution deposition technique. The anneal optimized Ta2O5 based thin film possessed an enhanced dielectric constant (epsilon(r)=45.6), low dielectric loss (tan delta=0.006), high film resistivity (rho=10(12) Omega-cm at E=1 MV/cm), excellent temperature stability (temperature coefficient of capacitance of 52 ppm/degrees C), and excellent bias stability of capacitance (similar to 1.41 % at 1 MV/cm). Additionally, the permittivity and dissipation factor exhibited minimal dielectric dispersion with frequency. The dielectric passive buffer layer film was typified by a uniform dense microstructure with minimal defects, and a smooth, nano-scale fine grain, crack/pinhole free surface morphology. Optimization of the integration design configuration was achieved by evaluating two heterostructure processing protocols; ((1))a single anneal and ((2))a dual anneal process protocol. Our results demonstrated the dual anneal process, to be an excellent method for realizing the successful monolithic integration of BST with affordable Si substrates. This work also demonstrated that the coefficient of thermal expansion (CTE) mismatch between the Ta2O5 buffer and BST active thin films in the coplanar device design serves to enhance the dielectric tunability of the device. The impact of this materials integration technology will promote broad scale implementation of affordable On-The-Move (OTM) phased array antenna systems across a variety of advanced communications platforms.