Imagine that there are crystalline cities in your mobile phone!
By Patricia Kidd, Principal Scientist Materials Applications Research
In the 1980s when I first started learning about electronics and electronic materials, people would talk about global communications and I couldn’t quite visualize what that meant. Fast forward to now, and I, like almost everyone else, take it for granted that I can see and speak to someone on the other side of the world using my little mobile phone. Unless you are an electronics engineer, it can be very hard to know what’s going on inside the mobile phone. Even if you cut it open (don’t try this!) you won’t see very much.
However, at the heart of mobile phones, tablets and computers are complex arrays of semiconductor devices. They are called ‘semiconductor’ devices because they are mainly made from semiconductor materials such as silicon. The devices are connected together in integrated circuits and are like tiny crystalline cities. They have complex architectures with ‘buildings’ that create, store and destroy different forms of energy and signal. They have ‘roads’ that transfer information and energy to different places. Atoms are the ‘bricks’ of these cities. The equivalent of 1 kilometer in a city could be 1 millimeter in a mobile phone and as time goes on engineers become more capable of building smaller, faster and more energy-efficient ‘cities’.
The industry of semiconductor fabrication is very high-tech and very complex. Electronic engineers are the architects of the devices and crystal growers and fabricators try to realize their designs. Often defects cannot be tolerated in the structure, everything has to work as it was designed and there is very little room for error. At the heart of a good product is a thorough approach to quality. How do you achieve a quality of build? One vital action is to measure, measure and just to be sure measure again and do this at many stages of the building process.
Within the semiconductor industry, X-ray analysis such as that provided by PANalytical provides the crystal growers with an unrivalled non-destructive measuring ‘tape’. The divisions on our X-ray measuring tape are around 0.1 nm and our measuring tape can be in excess of 1000 nm long. This is just right for the kinds of dimensions used in the creation of the electronic devices. Our X-ray analysis is often used at the early stages of the fabrication process. Powder diffraction and X-ray fluorescence can be used to establish the quality of the raw materials used in the process. They are making sure that the building blocks (bricks) are of the right quality. High-resolution X-ray diffraction is used in crystal growth facilities and foundries, to measure the early stages of crystal growth, called ‘epitaxy’. Epitaxy could be considered analogous to preparing the foundations and the stories of the buildings, before the details are finalized. It is important to get the dimensions of epitaxy right otherwise the entire structure may either collapse or not work as expected.
Schematic diagrams such as that shown below are used in the industry, in this example, to depict the layers in a device such as a light emitting diode (LED). LEDs are used in displays, 3 light emitting diodes are used to create a single pixel and there are typically >100,000 pixels in a typical mobile phone display. The diagram is analogous to an architect’s illustration and is often accompanied by the expected dimensions of the layers (in nanometers) and the chemistry of the layers.
So, what’s our conclusion? It’s that to build something as extraordinary as a mobile phone you need some pretty special tools with some pretty special capabilities. Harnessing X-rays to become our tape measure is a skill that PANalytical has built up over the years. We’re proud to be players in the global communications revolution and a provider of tools used in the semiconductors supply chain.
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