Spectroscopy Articles

E.A.H. Timmermans and J.J.A.M. van der Mullen^*

Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands. E-mail address [email protected]

David Chenery and Hannah Bowring

Smith & Nephew Group Research Centre, York Science Park, Heslington, York YO10 5DF, UK

Introduction

Glow Discharge Mass Spectrometry (GDMS) is one of the most powerful solid state analytical methods for the direct determination of traces, impurities and depth profiling of solids.^1–5 Glow discharge mass spectrometers, which are commercially available with fast and sensitive electrical ion detection, allow direct trace elemental determination in solid materials with good sensitivity and precision in the concentration range lower than ng g^–1.⁶

Moore’s law* dictates microelectronics researchers to make integrated circuit (IC) devices smaller and to put them as close to each other as possible on a chip. This results in a better performance and a larger functionality of the chips. However, these devices also require a good electrical isolation from each other. This is in general done by the formation of a thick local oxide in the “field region” between the devices. In 1970, researchers from Philips¹ invented the so-called LOCOS (LOCal Oxidation of Silicon) technique to achieve this isolation. Using a Si₃N₄ mask, the silicon is thermally oxidised in the nitride-free field regions. Figure 1 (left) shows a typical LOCOS structure. Although LOCOS seemed a perfect solution at that time, it came with a lot of problems, many of them related to mechanical stresses. Thermal oxidation of Si to SiO₂ occurs together with a 125% volume expansion. As a result, the oxide grown in the field region, called the “field oxide,” exerts large forces on the surrounding silicon. Another major drawback of this technique is the so-called “bird’s beak,” caused by the lateral growth of the oxide under the nitride mask. This bird’s beak not only affects the intended device length, it also introduces large local mechanical stresses in the silicon, because of volume expansion, and it also deforms the nitride film. These stresses often resulted in the generation of dislocations in the silicon, which are quite harmful for the devices.

S.Y. Luk,^a N. Patel^a and M.C. Davies^b

^aMolecular Profiles Ltd, 1 Faraday Building, Nottingham Science & Technology Park, University Boulevard, Nottingham NG7 2QP, UK. E-mail: [email protected]
^bLaboratory of Biophysics and Surface Analysis, School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK

S.E.J. Bell,^a* E.S.O. Bourguignon,^a A. O’Grady,^a J. Villaumie^a and A.C. Dennis^b

^aSchool of Chemistry, The Queen’s University of Belfast, Belfast, BT9 5AG, Northern Ireland, UK
^bAvalon Instruments Ltd, 10 Malone Road, Belfast BT9 5BN, Northern Ireland, UK

Luis Oliveira and Manuel Pais Clemente

CETO – Centro de Ciências e Tecnologias Ópticas, Rua Caldas Xavier, Nº38, 6º E, 4150 Porto, Portugal. E-mail: [email protected]

An introduction to photoacoustic spectroscopy.

Chemical imaging spectroscopy is an exciting new analytical advance that answers commonly asked questions such as what chemical species are in a sample, how much of each is present, and most importantly, where are they located? Through the fusion of traditional infrared spectroscopy with powerful microscopic and macroscopic imaging capabilities, chemical imaging spectroscopy answers all these questions simultaneously, in a single rapid measurement.