Lau Wai Shing

Wai Shing Lau (born July 29, 1955 in Hong Kong) is also known as Lau Wai Shing. The family name of "Lau" is sometimes spelled as "Liu" like Liu Shaoqi or Liu Bocheng.

Biography

He got his bachelor degree from the Department Of Electrical Engineering, University of Hong Kong in 1977. Then he got his master's degree from the Department of Electronics, the Chinese University of Hong Kong in 1980. Subsequently, he published a paper on the analysis of constant-capacitance deep-level transient spectroscopy by negative feedback theory in 1982. He got his PhD in Electrical Engineering from the Pennsylvania State University, Pennsylvania, USA in 1987 by working on transparent conductive thin films like tin oxide, indium oxide and zinc oxide. Then he served as a post-doc in the same laboratory to work on PECVD silicon nitride samples from IBM.

Dr. Lau is an electrical engineer and also materials scientist. He worked on both Si-based and III-V based microelectronics. For example, he worked on gallium arsenide and gallium nitride devices and materials.

During 1997-1998, he worked on embedded DRAM technology in Chartered Semiconductor Manufacturing, Singapore. He studied the mechanism of under-sensitive test structures and over-sensitive test structures. He pointed out that if this is properly understood, electrical failure analysis can be more easily achieved by electrical testing at the test structure level instead of at the product engineering level. This will make the job of DRAM yield enhancement easier.

He was the first in making a correlation between the leakage current of ultrathin tantalum pentoxide (one of the high-k dielectric) films with defect states detected by zero-bias thermally stimulated current. Most scientists cannot see any relationship between the leakage current in tantalum oxide and the defect states detected by thermally stimulated current. Dr. Lau managed to see the relationship between the leakage current and the defect states and published his theory in various papers. He invented "zero temperature gradient zero bias thermally stimulated current" as a method to detect defect states in ultrathin high-k dielectric films. This was patented as US Patent 6909273 in 2005. (Please also see reference [1].) In addition, he has also developed a technique known as "two-scan zero-bias thermally stimulated current" when an insulator or semiconductor has some traps which can be filled at low temperature and some traps which can only be filled at relatively high temperature. (Please see reference [2].)

He also worked on Cu/low-k back-end-of-line (BEOL) technology. (Please see reference [3].)

He also wrote various papers on MOS transistors. For example, he worked on the application of strain engineering to CMOS technology. He pointed out that if tensile stress can increase the on current of n-channel MOS transistors, tensile stress will also increase the off current. Then he proposed a theory why tensile stress can improve n-channel MOS transistors even though there is an increase in the off current. (Please see reference [4].)

Dr. Lau also studied the theory of electron mobility in Si-based MOSFET. In 2005, Dr. Lau pointed out as Lau's hypothesis that "remote Coulombic scattering" is only important in the subthreshold region and in the region slightly above threshold. (Please see reference [5].)

Dr. Lau also explained the observation of anomalous narrow channel effect in very short p-channel MOSFET. This effect is relatively weak in n-channel MOSFET. (Please see reference [6].)

Besides semiconductor materials and devices research, Dr. Lau also works privately on the research of traditional Chinese medicine, chronic fatigue syndrome, irritable bowel syndrome, etc.

He has also worked on the application of infrared spectroscopy to semiconductor materials. He has published a book "Infrared Characterization for Microelectronics", World Scientific, Singapore, 1999.

References

[1] W.S. Lau, K.F. Wong, T. Han and N.P. Sandler, "Application of zero-temperature-gradient zero-bias thermally stimulated current spectroscopy to ultrathin high-dielectric-constant insulator film characterization”, Appl. Phys. Lett., 88, no. 17 (24 April 2006): article number 172906 (USA).

[2] W.S. Lau, "Similarity between the first ionized state of the oxygen vacancy double donor in tantalum oxide and the first ionized state of the cadmium vacancy double acceptor in cadmium sulfide", Appl. Phys. Lett., vol. 90, article number 222904, 2007.

[3] W.S. Lau, H.J. Tan, Z. Chen and C.Y. Li, "A comparison of various dielectric/metal sidewall diffusion barriers for Cu/porous ultra-low-K interconnect technology in terms of leakage current and breakdown voltage”, Vacuum, vol. 81, no. 9 (May 2007), pp. 1040-1046.

[4] P. Yang, W.S. Lau, V. Ho, C.H. Loh, S.Y. Siah and L. Chan, "Effect of tensile stress on the various components of the off current of n-channel metal-oxide-semiconductor transistors”, Appl. Phys. Lett., vol. 91, no. 7 (13 August 2007), pp. 073514-1 to 073514-3.

[5] C.W. Eng, W.S. Lau, D. Vigar, S.S. Tan and L. Chan, "Effective channel length measurement of MOS transistors with pocket implant using the sub-threshold current-voltage characteristics based on remote Coulomb scattering", Appl. Phys. Lett., vol. 87, no. 15 (10 October 2005) pp. 153510-1 to 153510-3.

[6] W.S. Lau, K.S. See, C.W. Eng, W.K. Aw, K.H. Jo, K.C. J.Y.M. Lee, E.K.B. Quek, H.S. Kim, S.T.H. Chan and L. Chan, "Anomalous narrow width effect in NMOS and PMOS surface channel transistors using shallow trench isolation", Proc. IEEE EDSSC 2005, pp. 773-776.