The Physics of Soft-Breakdown and its Implications for Integrated Circuits

As the gate oxide films get thinner with each technology node for silicon integrated circuits, the reliability of these films has been carefully scrutinized and vigorously debated. When these oxides get thinner than 2 nm, we find that PMOS reliability (defined as the time to form the first connected defect chain between substrate and the gate of any transistor) can no longer be guaranteed. At higher voltages, the appearance of such a defect chain leads to catastrophic failure. However, at the lower operating voltages of modern ICs, the appearance of such defect chains hardly perturbs the transistor characteristics (soft-breakdown), and circuits may function beyond the traditional reliability limits. In this tutorial, we explore the physics of these soft-breakdown events in a systematic way to show that oxide reliability may not be a fundamental roadblock to continued scaling of silicon integrated circuits.

Muhammad A. Alam

Muhammad A. Alam received the BSEE (1988) from Bangladesh University of Engineering and Technology, the M.S. (1991) from Clarkson University, NY, and the Ph.D. (1994) from Purdue University, IN, all in electrical engineering. From 1995-2000, Dr. Alam had been with Bell Labs, Lucent Technologies, as a Member of Technical Staff in the Silicon ULSI Research Department. Since 2001, Dr. Alam has been a technical manager, supervising the Reliability Group of IC Technology Department at Agere Systems - a spin-off of Lucent Technologies which specializes in the manufacture of electronic and optoelectronic devices. His research interest involves the physics of carrier transport in semiconductor devices, and he has worked on theoretical aspects of transport models, quasi-ballistic transport in bipolar transistors, MOCVD crystal growth, laser dynamics, and most recently, on the theory of oxide reliability and the mechanism of ALD crystal growth. Dr. Alam is a member of the IEEE and the Optical Society of America.

Bonnie E. Weir

Bonnie E. Weir received the B.A.,with honors, (1988) in physics from Swarthmore College, and the Ph.D. (1994) in physics from Stevens Institute of Technology, Hoboken, NJ. From 1988-2001, she was a Member of Technical Staff at Bell Labs, working for AT&T and then Lucent Technologies. She is currently with Agere Systems. Her former research areas include Rutherford Backscattering and Boron Delta-doping. She is currently active in experimental research on ultra-thin oxide reliability. She served as vice chair of the dielectrics subcommittee for the International Reliability Physics Symposium in 1999, holds a patent on dielectric breakdown detection and has authored or coauthored more than 50 technical papers.

Paul J. Silverman

Paul J. Silverman holds the B.S. in physics from Drexel University and the M.S. in physics from Purdue University. He joined Bell Labs in 1969, where he has worked on loudspeaker design, Rutherford backscattering spectrometry, scanning tunneling microscopy, and molecular beam epitaxy. He is now doingelectrical device characterization and dielectric reliability testing at Agere Systems (formerly Lucent Technologies' Microelectronics division), Allentown, PA.

R. Kent Smith

R. Kent Smith received the B.S.(1965) in electrical engineering, the M.S.(1967) in physics from Bucknell University, and the Ph.D. (1972) in physics from the University of Maryland. From 1972 to 1975, he was a Alexander von Humboldt Fellow at the Institut fuer Theoritische Physik in Frankfurt, West Germany and from 1975 to 1979, an Assistant Professor of Physics at Duke University. In 1979 he joined Bell Labs as a Member of the Technical Staff and is currently employed by Agere Systems. His research interests involve the simulation of of semiconductor devices and processes.