BST Capacitors for Cryogenic Focal Plane Arrays

Although imaging in the 8-12 micron spectral region has widespread uses, high background radiation result sin low contrast, and charge storage in SiO2 capacitors limits the signal-to-noise and the upper limit of the dynamic range. A major opportunity exists to increase the performance of IR focal plan arrays (IRFPAs) using high dielectric constant BaSrTiO3 (BST) films to increase charge storage at the forcal plan. ATM recently announced an ARPA research program to develop BST capacitors for 1-gigabit dynamic random access memories (DRAMs), and the team members include IBM, TI and Micrn Semiconductor. Although early in the effort, capcitors with 30 fF/mm2 with low leakage have been demonstrated on 150 mm wafers. Dielectric constant for the BST is greater thatn 550 for 1400A films. The objective of Phse I is to deposit Ba1-xSrxTi)3 thin films by chemical vapor deposition on 150mm Si wafers. The effort will build upon DRAM technology, while focusing on unique requirements of cryogenic analog storage capcitors. Santa Baraba Research Center will characterize dielectric and resistance properties at 78K for different Ba/Sr ratios and will develop capacitor and process specifications for integrating ferroelectric capacitors in high resolution IRFPA's in Phase II.