“I would say that hardware is the bone of the head, the skull. The semiconductor is the brain within the head. The software is the wisdom and data is the knowledge.”
— Masayoshi Son
Did you know that a half-trillion-dollar industry uses beach sand as a raw ingredient? — The very same sand kids play with, and adults lay on to catch some sun rays.
In today’s article, I’m going to share with you how this simple ingredient, AKA Sand, is among the raw ingredients of an enormous industry with an annual sales revenue of around $509 billion as of 2020.
This gigantic industry is known as the Semiconductor Industry. If you are not familiar with the term ‘Semiconductor,’ maybe you’ve heard the term ‘Transistor’? If not, then, for sure, you know what a ‘CPU’ is.
I will introduce the invention and the terms and then dive in and show how raw sand is being transformed into a CPU, i.e., “Gold.” The same processing unit sets inside your Computer or Smartphone, empowering all the magic happing on its screen.
The most important invention of the 20th century
“Necessity is the mother of Invention” — Plato.
Behind each invention, there is a concealed necessity; In the case of the transistors, the need was very pressing.
The world needed a tiny device that could switch quickly between conducting to insulating state — and that was required to generate streams of binary digits 0/1, where 0 means that the device is insulating, i.e., is outputting a 0, and 1 means that the device is conducting, i.e., is outputting a 1.
Picture it this way.
To generate a binary number, e.g., ‘101010’ that could be translated at the end of its journey through your device to any color, number, or letter you see on the screen — A switch is needed to output a ‘1’, then a ‘0’, then a ‘1’ again, and so on, until the required number ‘101010’ is entirely generated.
How did semiconductors come to the rescue? Read on to find out.
What is a Semiconductor?
While metals are excellent conductors and will be continuously conducting electricity, plastic, on the contrary, is an insulator and will not be conducting any electricity at all.
A semiconductor is a mix(hence it is a ‘Semi’ conductor); it can be both. And altering some of its properties will turn it from an insulator to a conductor and vice versa.
To add some clarity, suppose we use silicon(a semiconductor) to conduct electricity — Then, by default, it would be insulating; however, it becomes a conductor when we add the right amount of heat to it.
And that is briefly the superpower of semiconductors.
What is a Transistor?
Heating is not the only way to turn a semiconductor into a full conductor.
For instance, silicon can be doped with Phosphorus/Boron, and doping will alter its characteristics in a way that applying a small amount of voltage to the right places would turn it from an insulator to a conductor.
Let me explain.
There are two types of doping, n-type and p-type, where n and p stand for negative and positive; furthermore, by taking pure Silicon and injecting Phosphorus into the two green regions(see the figure below), we create two n-doped regions, since Phosphorus has one extra electron in its atom.
Similarly, by injecting Boron into pure Silicon(see the red region in the figure below), we create a p-doped region since Boron has one less electron in its atom.
And finally, without any voltage applied to the base(see figure below), due to the reverse biasing caused by the p–n junction, i.e., the boundary between the n-doped and p-doped regions, the current will be blocked, and the transistor will act as an insulator.
However, applying a positive voltage to the base would result in forward biasing, which turns the transistor into a conductor.
On December 23, 1947, the transistor was successfully demonstrated at Bell Laboratories in Murray Hill, New Jersey.
This is the greatest invention of the 20th century. This non-mechanical tiny electric switch can be turned on and off by simply applying a small voltage to its base. It’s superfast ,tiny, and reliable.
But what about turning Sand into “Gold,” you might be wondering!
Let me show you how it’s done.
Semiconductor fabs(semiconductor fabrication plants — see figure below) are enormous factories requiring many expensive tools and devices to complete the microelectronics fabrication process.
Roughly speaking, a fab can cost between 3 to 20 billion dollars as of 2020.
The central part of a fab is the cleanroom(see figure below). Cleanrooms typically have a very high level of cleanliness, quantified by the number of particles(e.g., dust) per cubic meter.
FOUP(Front Opening Unified Pod) — FOUPs can load up to 25 wafers.
And finally, let’s see the process.
From Sand to “Gold”
Step #1: Raw Sand
Silicon Dioxide is a natural compound of silicon and oxygen found mostly in Sand. Furthermore, this compound is the base ingredient for semiconductors manufacturing.
Step #2: Silicon Ingot
Sand is being transformed into Poly Silicon by means of a complex reduction and purification process, then to meet semiconductor manufacturing standards, chemical and physical methods are applied to turn it into a crystalline form, i.e., a purified monocrystal ingot(99.9999999% pure, one alien atom for every 1 billion silicon atoms).
Step #3: Wafers
The Ingot is then sliced into round wafers(see figure below). Usually, the size of one wafer would be 150/200/300mm. These wafers will become the substrate, i.e., the platform, for microchip development.
Step #4: Fabrication
The fabrication process will take place inside a semiconductor fab; Transistors will be created as the smallest control unit in a microchip.
During the process, FOUPs full of wafers will automatically go through plenty of steps, entering a tool after a tool. And each tool will follow a specified recipe.
Once the process is over, many patterned layers of various materials will be accumulated on the wafer surface.
Here’re some of the steps performed during the fabrication process:
Polish: The surface of the wafer is oxidized at 1000 degrees to produce a non-conductive layer.
Photoresist: Photoresist material(light-sensitive material) is uniformly distributed across the wafer’s surface using centrifugal force.
Photomask: A mask is used to filter the UV light projected onto the surface of the wafer so that only the places that are supposed to be etched(removed) would be exposed to light.
Etching: Etching(removing) the exposed areas.
Doping: n-type or p-type doping, using Ion implantation process to shot atoms into specific regions.
Metal Layers: Metal layers are created to interconnect the transistors’ gates to develop the expected binary logic, i.e., functionality.
The fabrication process is repeated many times.
Step #5: Microchips(“Gold”)
Once microchips are fully fabricated, the wafer can finally be sliced into small rectangular slices. Each slice is basically the microchip that will be integrated inside a CPU or a memory, etc.
Finally, the product will be packaged and ready to be shipped to customers.
Roughly speaking, the 10-nanometre transistors are 10,000 times thinner than a human hair. The US Department of Energy has recently created the world’s smallest transistor with a working one-nanometre gate, about 50,000 times thinner than a human hair.
With this huge advancement since 1947, coupled with the other revolutions in the fields of AI, Machine learning, and robotics, The sky is getting closer :)
This article is the first in a series of three articles:
⚫ Transistors: The Greatest Invention of the 20th Century.
⚫ Transistors: Let’s Time-Travel Together.