The Making of a Chip

[Leon]

From Sand to Silicon: the Making of a Chip

[Leon]

Sand -- With about 25% (mass) Silicon is – after Oxygen – the second most common element in the earth's crust. Sand – especially Quartz - has high percentages of Silicon in the form of Silicon dioxide (SiO2) and is the base ingredient for semiconductor manufacturing.




Melted Silicon -- scale: wafer level (~300mm / 12 inch) - Silicon is purified in multiple steps to finally reach semiconductor manufacturing quality which is called Electronic Grade Silicon. Electronic Grade Silicon may only have one alien atom every one billion Silicon atoms. In this picture you can see how one big crystal is grown from the purified silicon melt. The resulting mono crystal is called Ingot.

[Leon]

Mono-crystal Silicon Ingot -- scale: wafer level (~300mm / 12 inch) - An ingot has been produced from Electronic Grade Silicon. One ingot weights about 100 kilograms (=220 pounds) and has a Silicon purity of 99.9999%.



Composite illustration

[Leon]

 

Ingot Slicing -- scale: wafer level (~300mm / 12 inch) - The Ingot is cut into individual silicon discs called wafers.



Wafer -- scale: wafer level (~300mm / 12 inch) - The wafers are polished until they have flawless, mirror-smooth surfaces. Intel buys those manufacturing ready wafers from third party companies. Intel’s highly advanced 45nm High-K/Metal Gate process uses wafers with a diameter of 300 millimeter (~12 inches). When Intel first began making chips, the company printed circuits on 2-inch (50mm) wafers. Now the company uses 300mm wafers, resulting in decreased costs per chip

[Leon]

Applying Photo Resist -- scale: wafer level (~300mm / 12 inch) - The liquid (blue here) that's poured onto the wafer while it spins is a photo resist finish similar as the one known from film photography. The wafer spins during this step to allow very thin and even application of this photo resist layer.



Exposure -- scale: wafer level (~300mm / 12 inch) - The photo resist finish is exposed to ultra violet (UV) light. The chemical reaction triggered by that process step is similar to what happens to film material in a film camera the moment you press the shutter button. The photo resist finish that's exposed to UV light will become soluble. The exposure is done using masks that act like stencils in this process step. When used with UV light, masks create the various circuit patterns on each layer of the microprocessor. A lens (middle) reduces the mask's image. So what gets printed on the wafer is typically four times smaller linearly than the mask's pattern.

[Leon]

Exposure -- scale: transistor level (~50-200nm) - Although usually hundreds of microprocessors are built on a single wafer, this picture story will only focus on a small piece of a microprocessor from now on – on a transistor or parts thereof. A transistor acts as a switch, controlling the flow of electrical current in a computer chip. Intel researchers have developed transistors so small that about 30 million of them could fit on the head of a pin.



Washing off of Photo Resist -- scale: transistor level (~50-200nm) - The gooey photo resist is completely dissolved by a solvent. This reveals a pattern of photo resist made by the mask

[Leon]

Etching -- scale: transistor level (~50-200nm) - The photo resist is protecting material that should not be etched away. Revealed material will be etched away with chemicals.



Removing Photo Resist -- scale: transistor level (~50-200nm) - After the etching the photo resist is removed and the desired shape becomes visible

[Leon]

 

Applying Photo Resist -- scale: transistor level (~50-200nm) - There's photo resist (blue color) applied, exposed and exposed photo resist is being washed off before the next step. The photo resist will protect material that should not get ions implanted.



Ion Implantation -- scale: transistor level (~50-200nm) - Through a process called ion implantation (one form of a process called doping), the exposed areas of the silicon wafer are bombarded with various chemical impurities called Ions. Ions are implanted in the silicon wafer to alter the way silicon in these areas conducts electricity. Ions are shot onto the surface of the wafer at very high speed. An electrical field accelerates the ions to a speed of over 300,000 km/h (~185,000 mph)

[Leon]

Removing Photo Resist -- scale: transistor level (~50-200nm) - After the ion implantation the photo resist will be removed and the material that should have been doped (green) has alien atoms implanted now (notice slight variations in color)




Ready Transistor -- scale: transistor level (~50-200nm) - This transistor is close to being finished. Three holes have been etched into the insulation layer (magenta color) above the transistor. These three holes will be filled with copper which will make up the connections to other transistors.



Electroplating -- scale: transistor level (~50-200nm) - The wafers are put into a copper sulphate solution as this stage. The copper ions are deposited onto the transistor thru a process called electroplating. The copper ions travel from the positive terminal (anode) to the negative terminal (cathode) which is represented by the wafer.

[Leon]

 

After Electroplating -- scale: transistor level (~50-200nm) - On the wafer surface the copper ions settle as a thin layer of copper.



Polishing -- scale: transistor level (~50-200nm) - The excess material is polished off.



Metal Layers -- scale: transistor level (six transistors combined ~500nm) - Multiple metal layers are created to interconnect (think: wires) in between the various transistors. How these connections have to be “wired” is determined by the architecture and design teams that develop the functionality of the respective processor (e.g. Intel® Core™ i7 Processor ). While computer chips look extremely flat, they may actually have over 20 layers to form complex circuitry. If you look at a magnified view of a chip, you will see an intricate network of circuit lines and transistors that look like a futuristic, multi-layered highway system.