DRAM
High-k dielectrics for future DRAM cell technologies

DRAM: -1-   -2-   -3-   -4-

       

Selected Publications - 2007:

 

1) SR-XPS study on the interface chemistry of high-k Pr_xAl_2-xO₃ (x = 0 to 2) dielectrics on TiN for DRAM applications

T. Schroeder, G. Lupina, R. Sohal, G. Lippert, Ch. Wenger, O. Seifarth, M. Tallarida*, and D. Schmeißer*

IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany

* BTU Cottbus, PF 101344, 03013 Cottbus, Germany

Journal of Applied Physics, 101, 014103 (2007)

 

Engineered dielectrics combined with compatible metal electrodes are important materials science approaches to scale three-dimensional trench dynamic random access memory DRAM cells. Highly insulating dielectrics with high dielectric constants were engineered in this study on TiN metal electrodes by partly substituting Al in the wide band gap insulator Al₂O₃ by Pr cations. High quality PrAlO₃ metal-insulator-metal capacitors were processed with a dielectric constant of 19, three times higher than in the case of Al₂O₃ reference cells. As a parasitic low dielectric constant interface layer between PrAlO₃ and TiN limits the total performance gain, a systematic nondestructive synchrotron x-ray photoelectron spectroscopy study on the interface chemistry of Pr_xAl_2-xO₃ x=0–2 dielectrics on TiN layers was applied to unveil its chemical origin. The interface layer results from the decreasing chemical reactivity of Pr_xAl_2-xO₃ dielectrics with increasing Pr content x to reduce native Ti oxide compounds present on unprotected TiN films. Accordingly, PrAlO₃ based DRAM capacitors require strict control of the surface chemistry of the TiN electrode, a parameter furthermore of importance to engineer the band offsets of Pr_xAl_2-xO₃ /TiN heterojunctions.

PDF published by AIP Journals (http://journals.aip.org)

 

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2) Morphology and composition of Praseodymium-based high-k materials and their relevance to dielectric properties of thin films

G. Lippert, J. Dabrowski, I. Costina, G. Lupina, M. Ratzke*, P. Zaumseil, and H.J. Müssig

IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany

* BTU Cottbus, PF 101344, 03013 Cottbus, Germany

ECS Trans. 6, 773 (2007)

 

We discuss some of the issues associated with the relation between the leakage current and the dielectric constant on the one hand, and the crystallographic structure and the chemical composition of the film on the other. We compare the technology requirements for various applications, the open questions, and the known answers and physical mechanisms. We focus mostly on dielectrics containing Pr oxides. Starting with the binary Pr₂O₃, we investigate electronic properties and formation energies of point defects as revealed by ab initio calculations and we attempt to associate this data with the experimental information on the influence of processing on the dielectric quality of the film. We then consider Pr silicates on Si for MOSFETs and Pr_xAl_2-xO₃ on TiN for MIM front-end applications. In the latter case, annealing above about 800°C needed to noticeably increase the effective dielectric constant causes an increased leakage. In this context, we discuss the diffusion mechanism for Ti and the influence of Ti on the leakage current.

PDF published in Journal of the Electrochemical Society (http://www.ecsdl.org/JES/)

 

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