The Theory of Nothing

How has the integrated circuit changed the world?

How has the integrated circuit changed the world?

This is a continuation of the post about the transistor. The integrated circuit is just a progression from the transistor when these wondrous electronic gadgets were made more efficiently by putting several of them on a single slab of silicon. Someone got the brilliant idea of combining many transistor elements on one wafer of silicon by coating them with photoresist and using microphotography to image a complete circuit, which today include a calculator, microprocessor, memory bank, GPS processor, TV circuit, and appliance control circuit.

Jack Kirby at Texas Instruments made the first working integrated circuit in July 1958, but it wasn’t to well into the sixties that practical circuits were made. They were essentially just curiosities back then.

One of the main problems in the manufacturing of an integrated circuit is producing a pure silicon crystal cylinder of sufficient size and then slicing it into thin round wafers that are flat to the wavelength of light. The next problem is the method of coating a high-resolution photoresist (a mixture that contains a small chain polymer dissolved in a solvent) on the wafer with no defects (bubbles, dirt, or unevenness). A photoresist is what its name suggests. It’s a film layer that hardens when exposed to ultraviolet light so that the unexposed areas can be washed away to leave a solid image.

The manufacture of integrated circuits is automated and done in a clean room. Anyone that goes into the room has to wear suits that cover everything but his or her face and be subjected to an air shower to remove contaminating dust or dirt.

A high-resolution negative with the microcircuit design is exposed using a precise imaging camera onto the photoresist layer and then a solvent is used to remove the unexposed areas. The wafer is then subjected to doping to produce the proper transistor type and orientation. There are more advanced methods of developing the exposed photoresist, one of which is using plasma in a vacuum to erode the unexposed areas out of the wafer. Also, this photoresist method is used to create interconnecting wiring using vacuum copper depositing.

Most modern integrated circuits require multiple exposure steps, all requiring high precision and absolutely clean methods. After the exposing and doping processes are completed, the individual rectangular chips are cut from the wafer using an amazing rotating blade and then automatically soldered to the leads in a plastic package with pins that we call a chip.

Recently, 300 mm diameter wafers are being used; element size has been reduced to 32 nanometers or less; and yields have increased to cut the cost of manufacturing.

Most integrated circuits are installed in thin inline packages, which allow for a high pin count and a very small size. Think of how small the processor in your smart phone is. This is only possible because of the amazing advances that have been made in integrated circuit manufacturing.

Integrated circuits are used in many devices and systems, including computers, cellular phones, appliances, automobiles, GPS devices, digital watches, MP3 players, military weapons systems, and a host of other things we don’t even think about. Thanks to some very clever people, we have these wondrous devices that would have been considered science fiction only a few decades ago.

Thanks for reading.