dielectrics for future stackedcapacitor DRAM Thin films of barium-strontium titanate (Ba,Sr)TiO 3 (BSTO) have been investigated for use as a capacitor dielectric for future generations of dynamic random-access memory (DRAM). This paper describes progress made in the preparation of BSTO films by liquid-source metal-organic chemical vapor deposition (LS-MOCVD) and the issues related to integrating films of BSTO into a DRAM capacitor. Films of BSTO deposited on planar Pt electrodes meet the electrical requirements needed for future DRAM. The specific capacitance and charge loss are found to be strongly dependent on the details of the BSTO deposition, the choice of the lower electrode structure, the microstructure of the BSTO, the post-electrode thermal treatments, BSTO dopants, and thin-film stress. Films of BSTO deposited on patterned Pt electrodes with a feature size of 0.2 m are found to have degraded properties compared to films on large planar structures, but functional bits have been achieved on a DRAM test site at 0.20-m ground rules. Mechanisms influencing specific capacitance and charge loss of BSTO films are described, as are the requirements for the electrode and barrier materials used in stacked-capacitor structures, with emphasis given to the properties of the Pt/TaSi(N) electrode/barrier system. Major problems requiring additional investigation are outlined.

The dielectric relaxation of Ba0.7Sr0.3TiO3 thin films was investigated up to K band (20 GHz) using time domain and frequency domain measurements. Our results show that from 1 mHz to 20 GHz, the dielectric relaxation of the complex capacitance of Ba0.7Sr0.3TiO3 thin films can be understood in terms of a power law dependence known as the Curie–von Schweidler law. The small dispersion (less than 7% decrease in capacitance from 1 mHz to 20 GHz) and low loss (loss angle less than 0.006 at 20 GHz) measured in Ba0.7Sr0.3TiO3 thin films indicate that these films are applicable to device application up to at least K band.

The discovery of luminescence in electrochemically etched porous silicon is an extremely important scientific breakthrough with enormous technological implications. It opens the door for silicon, the most important microelectronic material, as a possible material for optoelectronics applications. Our result, a correlation of Raman and photoluminescence spectra, shows that the observed luminescence is originated from extremely small microstructures. As the luminescent peak increases in photon energy, the Raman feature shifts to lower energy, remaining sharp, and eventually splits, developing into TO and LO modes. No peak at 480 cm−1 is observed, which indicates no substantial contribution from an amorphous region. These data provide strong evidence of the role of microstructures in porous silicon.

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