SBIR Phase II: Crystalline Ferroelectrics Combined with Transistor Technology

This Small Business Innovative Research Phase II project will focus on developing tunable microwave devices that utilize ferroelectric thin films for their electronic properties. Specifically, barium strontium titanate (BST) thin films are being used to develop new classes of tunable microwave devices, including phase shifters, delay lines and frequency-agile filters. Currently, these ferroelectric devices suffer from two drawbacks: easily formed planar devices demand very large tuning voltages on the order of 100 Volts , while easily tuned parallel plate devices require sophisticated processing techniques. These problems have inhibited the development of commercially viable components. The current project proposes combining silicon based circuitry with ferroelectric devices on the same substrate. For example, a silicon charge pump circuit can be integrated on-chip to provide high tuning voltages for a ferroelectric phase shifter. The voltage will be isolated to the chip and less than 3 Volts would be needed to externally drive the device. Combining silicon semiconductor technology with ferroelectrics will enable development of devices which take advantage of ferroelectric's dielectric properties and overcome the current roadblocks in the way of commercializing these devices. Commercially, a great deal of interest has emerged in the use of ferroelectric thin films in the wireless industry because of the material's ability to dramatically improve the functionality of existing devices. For example, a ferroelectric duplexer is possible which has one third the size of existing duplexers, while using 40% less power. Today's multiband handsets use up to four filters, so the potential for ferroelectrics is tremendous. A key wireless handset manufacturer identified at least six applications for tunable devices inside their telephones. Overall, the wireless telecommunications market has spawned the need for small, low power, high bandwidth microwave components. Over $50 billion of wireless handsets were sold in 2002, with $6 billion being spent on RF semiconductor components. With the trend towards highly functional wireless appliances like PDA's, the demand for wireless components will continue skyrocketing.