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This paper aims to provide details of MEMS (micro-electromechanical system) sensors produced from materials other than silicon.

Following a short introduction, this first considers reasons for using alternatives to silicon. It then discusses MEMS sensor products and research involving sapphire, quartz, silicon carbide and aluminium nitride. It then considers polymer and paper MEMS sensor developments and concludes with a brief discussion.

MEMS sensors based on the “hard” materials are well-suited to very-high-temperature- and precision-sensing applications. Some have been commercialised and there is a strong, on-going body of research. Polymer MEMS sensors are attracting great interest from the research community and have the potential to yield devices for both physical and molecular sensing that are inexpensive and simple to fabricate. The prospects for paper MEMS remain unclear but the technology may ultimately find uses in ultra-low-cost sensing of low-magnitude mechanical variables.

This provides a technical insight into the increasingly important role played by MEMS sensors fabricated from materials other than silicon.

This paper aims to report the influence of sputtering plasma deposition time on the structural and mechanical properties of the a-axis oriented aluminium nitride (AlN) thin films.

The AlN films were prepared using RF magnetron sputtering plasma on a silicon substrate without any external heating with various deposition times. The films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), atomic force microscope (AFM) and nanoindentation techniques.

The XRD results show that the AlN thin films are highly oriented along the (100) AlN plane at various deposition times indicating the a-axis preferred orientation. All the AlN thin films exhibit hexagonal AlN with a wurtzite structure. The hardness and Young’s modulus of AlN thin films with various deposition times were measured using a nanoindenter. The measured hardness of the AlN films on Si was in the range of 14.1 to 14.7 GPa. The surface roughness and the grain size measured using the AFM revealed that both are dependent on the deposition times.

The novelty of this work lies with a comparison of hardness and Young’s modulus result obtained at different sputtering deposition temperature. This study also provides the relation of AlN thin films’ crystallinity with the hardness of the deposited films.

The purpose of this paper is to present the characteristics of novel silicon Schottky barrier (SB) photodiodes (PDs) with aluminium nitride (AlN) (100 nm) nucleation layer.

Comparison was made with conventional silicon SB PDs.

It was found that smaller dark current could be achieved with AlN nucleation layer. It was also found that effective SB height increased from 0.65 to 0.71 eV with the insertion of the AlN layer. The dark leakage current for the Schottky PDs with the AlN layer was shown to be about two orders of magnitude smaller than that for the conventional silicon SB PDs.

It is possible that the detrimental effect of interface states situated near the metal semiconductor interface was less pronounced for the sample owing to the insertion of the AlN nucleation layer.

There is believed to be no other report on silicon SB PDs capped with an AlN layer in the literature. This paper describes the fabricated silicon SB PDs and reports on the electrical characteristics of the devices with an AlN nucleation layer grown at low temperature.

The purpose of this study is to design and develop a new functional coating system for aerospace AL7075-T6 alloy that would evaluate the mechanical properties of the coating.

This paper outlines the scratch adhesion characterisation of Cr/CrAlN coating using a combination of radio frequency (RF) and direct current (DC) physical vapour deposition (PVD) magnetron sputtering. The surface morphology, microstructure and chemical composition of the Cr/CrAlN film were evaluated by optical microscopy (OM), field emission scanning electron microscopy (FESEM) integrated with energy-dispersive X-Ray spectroscopy (EDX) and atomic force microscopy (AFM). The film-to-substrate adhesion was measured by a scratch test machine manufactured with a detection system, motorized stages, penetration depth sensors, optical microscope and tangential frictional load sensors.

The AFM and ultra-micro hardness results showed an increase in surface roughness to about 20 per cent and hardness to about 74 per cent. Moreover, the film-to-substrate adhesion strength of 1,814 mN was obtained with PVD deposition process.

The main limitation of this work is caused by PVD deposition process. Besides, surface defects such as pinholes contribute to a decrease in adhesion strength.

The higher hardness of CrAlN coating is used to improve the properties of softer aluminium substrates. This hardness prevents ploughing-induced wear and provides greater adhesion strength by preventing coating delamination.

Until now, CrAlN is coated only on ferrous alloys. It has not yet been tried on aluminium alloys. Moreover, coating functionality depends on higher adhesion and failure mechanisms involved in the film-to-substrate system, which is significant in aerospace applications.

The purpose of this paper is to investigate the accuracy and repeatability of the indirect selective laser sintering of aluminium process.

This work characterised the shrinkage of indirect SLS aluminium parts during the various stages of production. Standard scale parts were measured using a Giddings and Lewis co‐ordinate measuring machine in both the green and infiltrated condition.

The experiments conducted show that most accuracy is lost during the furnace cycle and that the greatest loss of accuracy occurred in the Z dimension. Additionally the position of parts within the part bed in both X, Y and Z is shown to influence accuracy, with smaller parts being built closer to the edge of the bed later in the build. These results have been interpreted as being a result of the phenomenon of “Z‐growth”. Finally, the research shows that the overall accuracy of the indirect selective laser sintering of aluminium process is comparable with many existing processes such as investment casting.

Before any new material can be accepted, there is a need to not only fully characterise the dimensional accuracy attainable, but also to gain a thorough understanding of the processes that contribute to the inaccuracies. This paper addresses this need.

As the hybrid market changes, many hybrid companies are being forced to adjust to reduced defence budgets and to the encroachment of epoxy board based SMT on traditional hybrid areas. This paper considers the establishment of an intelligent power module technology as a viable way to utilise the strengths of hybrid technology, in a field where there is an expanding market and, at present, not too much competition. The basic techniques are described, some of the potential pitfalls are highlighted, and the likely scale of technical and personnel investment is indicated.

An overview of the concerns involved in the operation of electronic hardware at elevated temperatures is presented. Materials selection and package design issues are addressed for a wide range of packaging elements from the semiconductor chip to the box. It is found that most elements of common high density device and packaging architecture can be used up to 200°C. However, gold‐aluminium wirebonds, eutectic tin‐lead solder joints and die attaches, and FR‐4 boards will seriously degrade at temperatures below 200°C. For these elements, alternative materials of construction are recommended. Comparisons are made between package design for high power dissipation and that for high temperature operation.

ISHM invites papers for the above Conference, to be held on 29–31 May 1991 in Rotterdam, The Netherlands. Papers should cover areas such as: design, manufacturing, packaging and interconnection, materials and processing, applications, reliability, components, new technologies, marketing and economics, optoelectronics. Summaries should be in English, length 200–300 words. The deadline for receipt of summaries is 30 September 1990. (For full details, see announcement on pp. 54–55.)

In this paper, thermal analysis for a 1,200 A, 3.3 kV insulated gate bipolar transistor (IGBT) module was investigated and analysed using the three‐dimensional transmission line matrix (3D‐TLM) method. This paper also reviews the present status of the use of various thermal heat spreaders such as AlSiC MMC, Cu‐Mo and graphite‐Cu MMC and compares these with copper based heat spreaders and the use of aluminium nitride (AlN), diamond and BeO as substrates and their effect to dissipate the heat flux in heat sources localised in IGBT module design. The TLM method was found to be a versatile tool which is ideally suited to the modelling of many power electronic devices and which proved very useful in the study of transient thermal effects in a variety of device structures.