8.3.1 Fluorine-based etching of silicon

Given the noxious chemistry needed to etch silicon with a liquid, it is perhaps surprising that a gas can do the job at all. However, both xenon fluoride (XeF2) and chlorine trifluoride (ClF3) gases have been used successfully for just this purpose. Each acts as a source of fluorine atoms, which are just barely bound together into molecules and are easily rearranged around silicon atoms with which they form strong bonds, turning them into inert SiF4 gas. These
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7.4.4 Plasma-enhanced CVD (PECVD)

In PECVD a plasma is initiated in the CVD chamber, usually by supplying an RF voltage to the platen on which the wafer sits – the chamber geometry is similar to a reactive ion etch chamber. Ions are accelerated from this plasma onto the wafer surface, so that the CVD reaction is initiated not only by heating the wafer, but also by the energy imparted as the ions land. This allows high-quality film deposition at much lower wafer temperatures and higher deposition rates than unenhanced CVD, w
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7.4 Depositing compounds

As well as conducting metal layers, device fabrication requires dielectric, insulating materials and these are mostly chemical compounds rather than simple elements or alloys. By far the most widely used of these is silicon oxide (either as a glass or as crystalline quartz), but other oxides and nitrides are also common, plus polymers and a selection of more exotic materials.

Such compounds generally have very high melting points, or decompose under heating, so cannot be deposited by ev
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7.3.4 Physical vapour deposition (PVD), sputtering

An ion hitting a metal surface after acceleration through more than 100 V will not stick or bounce off but will burrow into the surface, splashing atoms outwards. This is known as sputtering and provides a versatile alternative to thermal evaporation for metal-vapour deposition: more controllable, with adjustable uniformity, able to cope with alloys and high-melting-point metals and suitable for production-line automation. Given these advantages, it is also worth the effort to heat the
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6.6 Oscillators in general

Although this section has dealt only with mass-spring systems, the analysis can be extended to any system where there is an oscillating driving force acting on a mass which is located by a restoring force. In fact, the analysis is even more general than this and can be applied to electronic networks where voltages and currents oscillate in much the same way as the mass on the spring.


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6.2 Natural frequency of free oscillations

Most of us have a fairly accurate understanding of what is meant by resonance – it's what causes a bell to continue to make a sound long after it has been struck. Yet this is just one example of resonance, a phenomenon that occurs in nature in a surprisingly large number of places.

It is all to do with the reversible transfer of energy from one form to another in a system. The common feature associated with mechanical systems that are able to store energy by oscillating is that they h
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5.2 Material comparisons

I want to depart from the specific example of the bicycle to make some more general points.

In most simple structural analysis the self-weight of the structure is ignored, as it is considered to be small in comparison with the loads carried. However, as an illustration of engineering practice in the search for efficient structures to employ in product design, it is worth examining how the strength and weight of particular materials compare.

These comparisons are illustrated throug
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2.5 Making multiple copies

Berliner was aware that Edison had problems duplicating cylinders. Initially copies were made from a master cylinder using a mechanical engraving process. Unfortunately this method caused the master cylinder to wear out after making just a few copies, so performers had to be asked to record several masters to ensure enough cylinders could be duplicated. An improved recording system allowed multiple master cylinders to be made by feeding several recording phonographs from one horn, but the cyl
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1 Capturing sound

Have you ever listened carefully to a recording of your own voice?

In this first activity, I want you to make a short recording of your voice.

Activity 1 (Optional)

Note: This optional activity requires the use of a
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Acknowledgements

The following material is Proprietary and is used under licence:

Text

Naughton, J. (1998) ‘Arts: Internet: It's free and it works. No wonder Bill Gates hates it’, Observer, 8 November 1998, © Guardian News and Media Ltd 2005;

Wilkins, E. (1994) ‘Rescued from £1 a day for girl's upkeep’, The Times, 31 January 1994. Copyright © Times Newspapers Ltd 1994;

‘Agency demands 1p from father’, The Time
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3.2 Being aware of the constraints and possibilities of the observer

It is often claimed that the essence of a systems approach is that of seeing the world in a special way. This immediately prompts the question of what is meant by the phrase ‘seeing the world’. Because we live so intimately with the world of objects, categories and people and phenomena, we tend to think our own way of seeing the world is the only way, or even of thinking, ‘Well that is my view because the world is like that’. Actually, your view is special in several separate ways.
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11.5.5 Chance

Another important source of inventions and scientific discoveries is chance, which is strongly associated with acts of insight. As well as the sort of painstaking work that either precedes an invention or goes into the steady improvement in performance, in the development of most inventions there's a moment when chance plays a part. Often people are looking for one thing but find another – perhaps working on one technology when they stumble on the principles behind another. The skill of the
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5.14 Compact fluorescents and new developments

In the case of the electric light there were a series of incremental product innovations (metal filaments, gas filled bulbs, frosted bulbs) as well as process innovations (some of which were mentioned above), which steadily improved performance and reduced price until, by the 1930s, the incandescent light was mature and diffused in many nations.

Then in the mid-1930s a new invention appeared that was to challenge the incandescent lamp – the fluorescent lamp. This was the culmination o
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4.1 An explanation

I will now elaborate on my answer from Exercise 1. I'm doing this because my internet search revealed more than I've written in the above answer, and to show that the invention of the telephone and its use by consumers is not as plain and simple as you may think. You we
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1.2.4 Conveying information to others

Diagrams are used extensively in most types of texts, but why do authors use them? There are two main reasons:

  • to illustrate what something looks like;

  • to demonstrate how objects or ideas or quantities are organised or related.

But there is also a subsidiary reason I hinted at. Authors also use diagrams:

  • to decorate and enhance the text to make it more pleasing to read.


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Learning outcomes

After reading this unit you should be able to:

  • appreciate diagrams as a powerful aid to thinking and acting;

  • distinguish between systems diagrams and diagrams helpful in systems work;

  • demonstrate sufficient skills to ‘read’ and ‘draw’ a wide range of diagrams, following given conventions, that help improve your understanding of a situation;

  • select diagrams suited to the needs of the situation you are investigating and the purp
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2 New products – old failings

This section introduces product ‘usability’. It offers a case study of a vegetable peeler to illustrate how usability issues exist alongside other important concerns in the product development process.

If you look around high-street or shopping-mall stores, you cannot help but notice the number and variety of new products on offer. This year's washing machine or dishwasher, stylish furniture, multi-feature telephones, audio systems, DVD players, digital cameras and camcorders, all b
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2.7 Infiltration

Entry of precipitation through the soil surface and on downwards, by gravity, is known as infiltration. The rate at which this process can take place is governed by the permeability (a measure of the ease with which water can flow through the subsurface layer) and by the existing degree of saturation of the soil. Infiltration can be impeded by outcropping impermeable rocks or by paved areas, and also by the presence of finegrained soils with a low permeability (such as clay). At certain times
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3.5 Design of the bridge

The design of the original structure was governed by applicable standards in 1926. The official inquiry found that the design and build fell within those limits, the most important being the allowable stress in the eye-bar chain of 345 MPa. The steel was to be made with a maximum elastic limit of 520 MPa, with a safety factor on the strength of the steel of 2.75. It was argued at the time that over 70 per cent of the load was from the self-weight of the structure. Other suspension bridges of
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