How a Rock Becomes a Smartphone CPU

1. Quartz

Your smartphone processor began his trip to the northwest corner of Spain, in Mina Serrabal, a quartz mine near the city of Santiago de Compostela. Quartz – or more technically, silicon dioxide or silica – is the main component of sand. But at Serrabal, he may have come in huge parts twice the width of a smartphone. The iron mine operator manages an automated system to sort the silica by size. After the parts are washed and treated, the large ones go to the Atlantic coast for the next stage of the trip.

2. Silicon metal

After an hour by truck, the quartz mini-toules arrive in Sabón, the 125,000 square meter of ferroglobe factory in the coastal province of a Coruña. Here, quartz will be mixed with dehydrated wood chips and heated to 1,500 to 2,000 ° C in a trio of electric arc overalls which use massive electrodes invented in this plant in the 1990s. Inside the oven, a reaction takes place which tears the oxygen of silica and wood carbon glue. The result is metal silicon and carbon monoxide.

3. Polysilicon purified

The resulting silicon metal is around 98% pure, and it is not good enough. It should be at least 99.99999999% pure to become a microprocessor, which will require fairly powerful chemistry. He therefore left for Wacker Chemie, Burghausen, Germany. Here, the metal undergoes what is called the Siemens process: it is bathed in hydrochloric acid and reacts to form gas hydrogen and a liquid called trichlorosilane. All impurities will be in the liquid, which is then carried out through a process of distillation in several stages which separates the pure trichlorosilane from all that is undesirable. Once the necessary purity is reached, the reaction is reversed: at 1,150 ° C, the trichlorosilane is reacted with hydrogen to deposit several silicon crystals, called polysilicon, and the resulting chlorcome acid gas is sucked. The polysilicon forms thick stems around the heating elements. Once it has cooled and removed from the reaction chamber, the polysilicon is broken for shipping.

4. Wafers in silicon

UltraPure Silicon is made up of many crystals with different orientations. But microprocessors must be made from a single crystal. The equipment could therefore migrate to Sherman, Texas, where Globalwafers recently opened a factory of US $ 3.5 billion. Here, the polysilicon is put through what is called the Czochralski (CZ) method. In a high purity quartz crucible, the polysilicon is heated to approximately 1,425 ° C and melted. Then, a seed crystal with a precise crystal orientation is immersed in the cast iron, slowly attracted upwards and turned. Do all of it Exactly Right, and you will draw a pure and crystalline silicon strip which measures 300 millimeters in diameter and several meters high. Specialized saws then cut this pillar of semiconductor purity in platelets less than 1 millimeter thick. The platelets are cleaned, polished and sometimes treated, before heading to Fab.

5. Transformed refines

Now he has gone to Tainan, in the south of Taiwan, where the TSMC Fab 18 will transform these slices into the last smartphone processors. It is an extremely complex process, involving some of the most complex and expensive equipment on the planet, including EUV lithography systems that can cost more than $ 300 million each. In Fab 18, each slice will go through extremely precise months of torture to produce the transistors and the wiring that make up the processors. An extreme ultraviolet radiation will print patterns on it, the hot ions will affect its surface, the chemical reactions of precision will accumulate certain parts an atomic layer at the same time, the acids will climb the structures on a nanometric scale, and the metals will be electrochemically and will be polite in others. The result: a slice full of identical processors.

6. Packed chips

As amazing as these processors are, you cannot use them in this form. They must first be packed. For our silicon, this will happen in ASE facilities in Penang, Malaysia. A package provides the chip with mechanical protection, a way to remove heat and a way to connect the parts at the micrometers of the chip to parts on a millimeter scale of a printed circuit card. To do this, the pads are first lying in chips. Then, tiny weld balls, some dozens of micrometers through, are fixed to the fleas. The weld bumps are aligned on the corresponding parts of the packaging, and the two parts are melted together. It becomes more and more common that several pieces of silicon are integrated into the same package, stacked on each other or positioned next to each other on a separate piece of silicon called interposing. Other steps in the process follow and the packaged part is now ready for its next step.

Global trade