A microchip can consist of millions of transistors, creating a digital circuit. Silicon wafers go through many stages before the fabrication process is finished. A wafer is covered with a light sensitive chemical known as photoresist. Then, a specific shadow is cast upon the wafer.

The photoresist will react to the pattern of light and shadow, and harden or not depending on which area it's located in. The still soluble portions of the photoresist are then washed away, and the wafer is exposed to various chemicals that react with the silicon. Any hardened photoresist will protect the silicon it still covers. Once this protection is no longer needed, the remaining resist is removed, and the process starts again.

The field of layout design is designing the pattern of light and shadow that is cast onto the silicon wafer. Since individual "masks" are used to cast these shadows, this type of work is also known as "mask design." While an circuit designer will design what the circuit does, a layout designer will design the physical geometry of the shapes created onto the silicon.

As such, an understanding of electronics is required. One very important consideration is resistance and capacitance. They will slow down a signal, making the chip respond slower. This will affect the speed of the chip. While functionally it works, it could be the difference between a 200MHz part and a 266MHz part. A layout designer must keep that in mind, while drawing the layout.

Layout design is an interesting field to get into. This series of web pages are an introduction into the field, and are intended as a "pre class" and as a learning aid for someone currently in training.  For a formal class, contact your local college or university.