1. The transistors are the main part in the integrated chip. The concept behind an integrated chip is relatively simple: an entire electrical circuit with numerous transistors, wires, and other electrical devices all built into a single square of silicon. These chips are smaller than a centimeter-by-centimeter square, yet then can hold millions of transistors. If one person sat down to build all those miniscule parts and then connect them, it would take a whole year. But companies turn out several million integrated chips every few seconds - that's about the time it took you to read this sentence.
2. The reason integrated chips are possible at all is because engineers learned ways to build layers, making millions of transistors across the chip all at the same time. The first ideas on how to build the chips were developed by Jack Kilby and Robert Noyce in 1958, and they've been developed further over the years.
3. The chip is build upwards, layer by layer. Each layer is made by putting masks with particular patterns over the silicon and then altering the qualities of the silicon — or perhaps putting down metal or insulators - in the exposed parts.
4. The chip is made out of a semiconductor crystal. The chip starts out as a thin wafer of p-type silicon.
This is then coated with a layer of silicon dioxide — kind of a silicon rust, which doesn't conduct electricity. On top of this is placed a chemical called photoresist. Flashing a pattern of light (like the grid of light and dark that's formed by a window screen) on the photoresist turn any parts exposed to the light hard. The bits left in shadow stay soft. Then an etching chemical is applied those soft parts, and the silicon dioxide underneath them, are removed. The hard photoresist is then dissolved, leaving a pattern of raised silicon dioxide along the surface. Since the silicon dioxide doesn't conduct electricity, it keeps different parts of the final circuit separated from others.
5. Following the same method, a pattern of polysilicon (which does conduct electricity and is part of the transistor) is added. Then, again using projected photoresist masks, areas of the chip are doped to become n-type silicon, another crucial part of a transistor. Lastly, metal leads are added to connect the various components on the chip.
6. Since the chips are so small, hundreds are made on a single silicon wafer at once. After all the patterns have been faithfully reproduced on to the chips, the wafer is sliced up into individual chips.
III. After-text Exercises
1. Give equivalents of the following words and expressions:
мікроскопічні частини; певні зразки; діелектрик; тонка пластина кремнію з дірковою провідністю; силіконовий захист; хімікат; фоторезист; травити на металі; розчинити(ся); фоторезисторні рамки (шаблони), що проектуються.
2. Say whether the following statements are true or false:
a) The chips are bigger than a centimeter-by-centimeter square.
b) The first ideas on how to build the chips where developed in 1958.
c) The chip is built downward, layer by layer.
d) The chip starts out as a thin wafer of p-type silicon.
e) Since the silicon dioxide conducts electricity, it keeps different parts of the final circuit separated from others.
3. Answer the following questions on paragraphs 1-3:
l) What devices are built into a single square of silicon?
2) What is the reason integrated chips are possible?
3) When were the first ideas on how to build the chips developed?
4) How is the chip build?
5) What is each layer made by?