Publication

Nanoscale strain characterisation for ultimate CMOS and beyond

Mihai Adrian Ionescu, Kirsten Emilie Moselund
2008
Conference Papers

Abstract

Strain engineering is used to maintain Moore's Law in scaled CMOS devices and as a technology booster for More-than-Moore devices in the nanoelectronics era. Strain is crucial because of its ability to increase electron and hole mobilities in Si. However, accurate correlations between electrical performance and strain measurements are needed to enable the necessary feedback between materials, processing and devices to achieve best possible solutions. In this work, we outline new methods for sensitive 3D profiling of strain on a nanoscale. High-resolution vertical and lateral strain profiles applicable to both global (biaxial) and process-induced (uniaxial) strained Si devices are demonstrated. Raman spectroscopy is pushed to its present limit for precise analysis of strain in small geometry devices, including the use of tip-enhanced Raman spectroscopy (TERS) to improve the spatial resolution further. TERS maps are compared with atomic force microscopy data collected simultaneously and show that variations in surface morphology correlate directly with strain in the epitaxial layers. Sub-nm strain profiling is applied to strained Si and SiGe MOSFET channels. Strain is profiled across patterned uniaxial strained-Si-on-insulator structures and analysed in bended nanowire transistors. Finally strain is investigated across the channel regions of electrically measured SiGe p-MOSFETs. Good agreement between nanoscale strain measurements and finite element modelling is demonstrated. Sample preparation is included in the analysis and genuine effects of processing are investigated. (C) 2009 Elsevier Ltd. All rights reserved.

Official source

https://infoscience.epfl.ch/entities/publication/e886abb0-c6f3-4054-b898-4832c0a3d5b7

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Mihai Adrian Ionescu, Kirsten Emilie Moselund
2008
Conference Papers

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/e886abb0-c6f3-4054-b898-4832c0a3d5b7

About this result

Related concepts (32)

Deformation (engineering)

In engineering, deformation refers to the change in size or shape of an object. Displacements are the absolute change in position of a point on the object. Deflection is the relative change in external displacements on an object. Strain is the relative internal change in shape of an infinitesimally small cube of material and can be expressed as a non-dimensional change in length or angle of distortion of the cube. Strains are related to the forces acting on the cube, which are known as stress, by a stress-strain curve.

Strained silicon

Strained silicon is a layer of silicon in which the silicon atoms are stretched beyond their normal interatomic distance. This can be accomplished by putting the layer of silicon over a substrate of silicon–germanium (). As the atoms in the silicon layer align with the atoms of the underlying silicon germanium layer (which are arranged a little farther apart, with respect to those of a bulk silicon crystal), the links between the silicon atoms become stretched - thereby leading to strained silicon.

Silicon–germanium

SiGe (ˈsɪɡiː or ˈsaɪdʒiː), or silicon–germanium, is an alloy with any molar ratio of silicon and germanium, i.e. with a molecular formula of the form Si1−xGex. It is commonly used as a semiconductor material in integrated circuits (ICs) for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors. IBM introduced the technology into mainstream manufacturing in 1989. This relatively new technology offers opportunities in mixed-signal circuit and analog circuit IC design and manufacture.

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