From Sand to Silicon: How are microchips made?

From Sand to Silicon: How are microchips made?

Sand to Silicon – How are microchips produced?

The heart of modern processors - California’s high tech region got its name through the Silicon that is the bread and butter of the semiconductor industry. But how are microchips actually produced?

The process starts with sand. But not just any kind of sand or even beach sand. The particles that act as the starting point for silicon wafers are specifically mined, heated to thousands of degrees and purified to produce an ultimately flawless cylinder of silicon. The silicon is then sliced into wafers which are then polished. A photosensitive chemical is applied and then ultra violet light is shone through a “mask” like stencil to create the desired pattern on the silicon wafer. These patterns build the structure of the transistor layout the engineers have designed for this Integrated Circuit. However, because wafers are usually quite large, the process of shining light (called photolithography) through the mask must be repeated many times – often fitting hundreds or thousands of them on a single wafer. Each one will later become one single chip – a die.

In the next processing step, the wafer is washed in a solvent that dissolves the exposed areas of the photosensitive chemical, leaving a pattern exposed on the silicon. This pattern is then either etched or bombarded by ions, a process called implantation. The Ions are charged atoms which penetrate into the silicon due to their high velocity. This implantation process changes the electrical or physical characteristic in the area of the silicon in which they are implanted since each of the so-called dopant´s atoms can act as a charge carrier.

In the further processing, certain parts of the wafer may be filled with polysilicon or metal (this process step is called deposition) and is done to create transistor gates and interconnects. Following this process – the gates are connected through rigid copper interconnects – which are essentially tiny wires that are applied on top of the transistors with a similar ultra violet and etching process. How exactly they are connected depends on the architecture the engineers have decided upon. To avoid the interconnects from touching and short circuits to come about, this process is carried out in many layers.

Eventually tests are carried out to ensure the circuit on the die performs as desired. Due to the complexity and numerous processing steps, there are always failing dies due to manufacturing problems, even though this process is carried out in sterile environments with heavily automated equipment. Nonetheless, the good dies are identified, packaged, processed and sent all around the world.