What is Required for Semiconductor Chip Production
Semiconductor production falls into three main areas; silicon wafer creation, circuit construction, and packaging. The creation of silicon wafers is a complex task as it requires careful temperature control and drawing of the single crystal ingot at 1000°C. If the crystals are drawn out too quickly, or the temperature variance is greater than ±1°C, then the crystal will either be unusable or produce low yields. One created, the ingot is cut to size and then diced up into individual plane wafers. This is where the second stage steps in.
Integrating a circuit onto a silicon wafer involves lots of repeated steps as each layer is built up one by one. The first layer is what defines the transistor devices themselves (creating P and N regions), while the layer above this defines gates and interconnects to the layers above. After this, each layer above is used to route signals in metallic layers that connect all the components to create an integrated circuit. The top layer brings out the I/O to the circuit onto large metallic pads which is what the last step utilises.
The last step takes a wafer, splits it up into individual die, and then mounts them into their IC packages. From there, wires are bonded from the metal I/O pads on the die to pads on the IC package which then carries those connections to pins on the package.
While there are many precursor products needed to produce semiconductors, most are commonly available components including
- Hydrofluoric, hydrochloric, and sulphuric acid
- UV exposable etch resists (used in the PCB industry)
- Metals including aluminium, tin, and gold
- Inert gasses such as Nitrogen
- Oxygen for oxide growth
So, if producing semiconductor circuits uses easily obtainable chemicals, why is it so difficult to set up a foundry?