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5.3 Appreciating your basis for understanding

In my experience, the explanation that Fell and Russell suggest (i.e. that we each construct our own version of reality and therefore cannot be an objective observer; which in turn means we have to take responsibility for our observations and explanations) is challenging for many people. When I attend workshops where these ideas are expressed for the first time, people often become angry. You may be able to identify with them. If so, please try to use your discomfort productively for your own
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5.1 The state of ‘Being’

The structure of Section 5 is set out in Figure 8. Use this as a way of keeping track of the argument I am making.

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3.2 Making sense of the metaphor

The metaphor of the juggler keeping the four balls in the air is a powerful way for me to think about what I do when I try to be effective in my practice. It matches with my experience: it takes concentration and skill to do it well. But metaphors conceal features of experience, as well as calling them to attention. The juggler metaphor conceals that the four elements of effective practice often seem to be related. I cannot juggle them as if they were independent of each other. I can imagine
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3.1 Introduction

I wonder if you experience complexity in your daily life? For much of the time I struggle to keep my head above water as I try to understand and manage the complexity I experience as part of everyday life. I find social commentator and cartoonist Michael Leunig's depiction of a solitary figure looking through an ‘understandascope’ (Author(s): The Open University

2.4 Review

In working through this section, you have identified some of your initial expectations and I have explained some of what I think you will discover as you work through the unit. It would be appropriate at this point to look at some of the questions I asked you about your expectations again and note ways your expectations have changed.

Spend a total of around 30 minutes on the next three activities.

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2.3 Appreciating epistemological issues

Common sense tells me my experience and understanding of the world are limited. I am 173 cm in height. That limits my view of the world. It may not matter much that I cannot see what my house looks like from above but it does mean there will be things going on in the roof I may not notice until they impinge on areas that I can experience.

More significantly, there is a real limitation on understanding the experiences of other people. You might tell me about your experience but your desc
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2.2 Taking responsibility for your own learning

Not much of this unit conforms to the traditional pattern I mentioned earlier – the theory-example-exercise pattern. In particular, you will find you are expected to discover much of it for yourself. Why is this? This is a legitimate question and deserves a full answer. One year, a student at a residential summer school complained I had not taught him properly. I was, he told me, an expert and so why did I not demonstrate how to tackle the problem he was working on and pass my expertise on
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1.1.1 Learning by experience

It's a familiar idea but it implies two activities: learning and experiencing. Both activities need to happen if I am to say that learning from experience has happened. Experiencing seems to have two components. The first is the quality of attention that allows me to notice the experience and its components. The second is memory. Calling experience to mind allows me to examine the experience and to think about it in ways that were not possible at the time. Learning is what I take away from th
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Keep on learning

Study another free course

There are more than 800 courses on OpenLearn for you to
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Conclusion

This free course provided an introduction to studying Engineering. It took you through a series of exercises designed to develop your approach to study and learning at a distance, and helped to improve your confidence as an independent learner.


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8.4.1 Open-loop control

Open-loop is the crudest way of controlling etch depth. It relies on ensuring that every aspect of the process that can affect the rate of progress of the etch is kept under tight control. This can add up to a sizeable list. Table 5 shows just some parameters that affect both wet and dry etching.

Whethe
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8.3.3 Reactive ion etching: chlorine/argon plasma etching of aluminium

In a reactive ion etch (RIE), a chemical reaction is used to weaken the bonding of the surface of the material and assist the sputtering process. This combines the high rate and selectivity of a gas-phase etch with the directionality of a sputter etch.

For example, consider aluminium etched anisotropically by a Cl2/Ar mixed-gas plasma, which etches at up to 1 μm min−1:

  • Power pumped into the plasma breaks the gases up, rel
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8.3.2 Sputter etching: argon ion etching of gold

One commercial process for cutting inkjet printer nozzles uses sandblasting. Not surprisingly, the surface finish is rather poor and there are issues with particles contaminating the devices. However, it is a physical process very like this that we need if we are to achieve a vertical etch profile.

The key is directed bombardment by highly energetic particles. When processing on the microscale, these particles are not sand grains but ions accelerated towards the surface by an electric f
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8.2 Wet etches: acids and bases

The simplest etches use a liquid solvent that converts the material into a soluble compound or a gas. Unfortunately, most materials used in micro-devices have few soluble compounds, so some very aggressive chemicals are needed to attack them. Here is a list of some of the most commonly used ones:

  • Hydrofluoric acid (chemical formula HF) is used to convert silicon dioxide into water-soluble H2SiF6 (plus some hydrogen and water). It
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8.1 Introduction

Etching is central to all forms of micro-device production, from microelectronics and memory through to microsystems technology. Although materials, geometries and feature sizes vary widely, etch processes have a few common features and requirements:

  • Etching acts by converting solid material into a gas or a liquid that can be pumped or flushed away.

  • It is usually restricted to the openings in a lithographically defined mask, and since th
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7.2.2 Step coverage (conformality)

Not all layers require precise thickness control. Sometimes all that matters is that the film coats the entire surface, including vertical walls and (most difficult) the corners at the bottom of deep holes.

For example:

  • We may require an insulating layer of oxide between two conductors.

  • A protective titanium nitride barrier layer prevents aluminium from diffusing into silicon, and an underlying titanium adhesion layer ensures that
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7.2.1 Thickness control and uniformity

Often, final device characteristics, such as the value of a capacitor, the threshold voltage of a transistor, the resistance per square in a thin-film resistor and the resonant frequency of an acoustic wave filter, depend strongly on the thickness of a deposited layer. Therefore it must be ensured that the layer thickness is the same at all points on the wafer, and on every wafer that comes off the production line. Specifications of ±1% uniformity and reproducibility are not uncommon, and so
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7.1 Introduction

Micro fabrication often involves multiple layers of different materials, each following a sequence of process steps, usually deposition/lithography/etching. The microelectronics industry has been a driver for many of these techniques and that momentum has carried over into the MEMS community. The treatment that follows covers examples from both industries.

The appropriate deposition technique depends on the purpose of the layer – a thin insulating barrier layer in a transistor or capa
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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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