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Film thicknesses of W, TiN, and TaSiN in a full-metal gate stack with photoresist masks were measured in real time during plasma etching with an in situ thickness monitor. The accuracy of such measurement was approximately AE1 nm. The monitor functions on the basis of the interference of plasma optical emission, reflected from the surface and base of the film. Although W and TiN have large absorption indexes, their thicknesses were more accurately measured when they became thinner. In particular, W thickness was estimated more accurately when it was smaller than approximately 10 nm.

We present results of a two-demensional (2D) numerical simulation of high-frequency noise in a short-channel metal-oxidesemiconductor field-effect transistors (MOSFET). Conventionally this noise in MOSFETs is treated as a thermal noise with a rather slow temperature dependence of the noise spectra. On contrary, the results obtained indicate that this dependence is more of an exponential kind, typical for a shot noise. Shot noise is conventionally related to a forward biased p-n junction where the current is mostly due to diffusion in the quasi-neutral region. We therefore speculate that most likely in short channel MOSFETs most of the high-frequency noise is produced not in the cut-off region of the channel but near the source side of the channel where diffusion current component is dominant.

Articles you may be interested inEvolution of titanium residue on the walls of a plasma-etching reactor and its effect on the polysilicon etching rate Study of the impact of the time-delay effect on the critical dimension of a tungsten silicide/polysilicon gate after reactive ion etching Effects of wall recombination on the etch rate and plasma composition of an etch reactor It was found that critical dimensions of high-k/metal gates obey the multivariate linear approximation with the precision of 3 = Ϯ 0.86 nm, whose explanatory variables are amounts of metal compounds remaining on the plasma reactor walls. To measure their amounts, the authors assumed they are proportional to amounts of atoms sputtered out by Ar plasma and falling onto a Si wafers placed on a wafer stage. In this study, effects of metal compounds of W, Ti, Ta, and Hf, which are used to construct full-metal/high-k gates, were measured. It was found that Ti and Ta compounds dominate the fluctuation of critical dimensions and the dependency of their amount on wafer numbers being etched obeys a simple difference equation. From these results, they can estimate and minimize the fluctuations of critical dimensions in mass fabrications.