Microtechnology: Microfabrication technology

Microelectronic and MEMS devices use the same fabrication technology, usually called microtechnology.
It consists in using material deposit, lithography patterning and material etch steps so that you've covered your wafer with one material layer at the beginning, and you leave it with just the pattern you wished. If you cycle these steps with different layers well enough, following a process, you can fabricate an integrated device. Simple to say, quite hard to do. This section is not intended to be an encyclopedia about microtechnologies, but it explains to curious people what technics a microprocessor or an airbag accelerometer need to be built.


First of all, let's explain some terms...
What we call microtechnology is the pack of tools and steps that allow processing of material at microscopic scale. This includes devices able to deposit few nanometers to several micrometers thick material layers on wafers, etching machines, lithography involved devices, etc.
Microtechnology is the common part in microelectronics, MEMS, microfluidics, etc.
When you hear microfabrication word, think it as the use of microtechnology to fabricate a micrometric/nanometric device, could it be a MEMS or a microelectronic integrated circuit.
Microtechnology should not been confused with nanotechnology. Modern microelectronic devices could be called nanoelectronic, because of their size! But nanotechnology word is already used for completely different ways of fabricating things. It rather involves complex physics to build devices starting from molecules, if not atoms, self-assembled, to get a functional device. So let's keep the word microtechnology to describe the fabrication tools used for MEMS and microelectronics, even if it reached nanometric size resolution.

As I said, microtechnology consists in depositing different kind of materials on a substrate (generally called wafer) and remove all we don't need to follow a pattern for each layer. In modern microelectronic/MEMS industry, there are tens of materials used, and sometimes several ways to deposit them following different parameters. For layers patterning, there are also several ways to etch the materials. Furthermore, parameters like temperature, adhesion, aspect ratios etc. play an important role in designing a process flow. The method for depositing materials, etching them, and patterning layers will be detailed in separated pages.