An electrical engineer explains how semiconductors are made

2. What do semiconductors do?

Semiconductors are how electronic devices process, store and receive information. For example, memory chips store data and software as binary code, digital chips manipulate data according to software instructions, and wireless chips receive data from high-frequency radio transmitters and convert it into electrical signals. These different chips work together under the control of software. Different software applications perform very different tasks, but they all work by switching transistors that control current.

3. How is a semiconductor chip made?

The starting point for the vast majority of semiconductors is a thin slice of silicon called a wafer. Today’s wafers are the size of dinner plates and are cut from single crystals of silicon. Manufacturers add elements like phosphorus and boron in a thin layer on the surface of the silicon to increase the chip’s conductivity. It is in this superficial layer that the transistor switches are made.

Transistors are built by adding thin layers of conductive metals, insulators, and more silicon to the entire wafer, sketching patterns on those layers using a complicated process called lithography, and then removing selectively these layers using computer-controlled plasmas of highly reactive gases to leave specific patterns and structures. Because transistors are so small, it is much easier to add layered materials and then carefully remove unwanted materials than to place microscopic lines of metal or insulators directly on the chip. By depositing, patterning and etching dozens of layers of different materials, semiconductor manufacturers can create chips with tens of billions of transistors per square inch.

4. How are today’s chips different from earlier ones?

There are many differences, but probably the most important is the increase in the number of transistors per chip.

Among the first commercial applications of semiconductor chips were pocket calculators, which became widely available in the 1970s. These early chips contained a few thousand transistors. In 1989, Intel introduced the first semiconductors to exceed one million transistors on a single chip. Today, the biggest chips contain more than 50 billion transistors. This trend is described by what is known as Moore’s Law, according to which the number of transistors on a chip will double approximately every 18 months.

Moore’s Law has stood for five decades. But in recent years, the semiconductor industry has had to overcome major challenges — primarily, how to keep transistors downsized — to keep up this pace of advancement.

One solution was to go from two-dimensional flat layers to three-dimensional layers with fin-like silicon ridges protruding from the surface. These 3D chips greatly increased the number of transistors on a chip and are now widely used, but they are also much more difficult to manufacture.

5. Do more complicated chips require more sophisticated factories?

Simply put, yes, the more complicated the chip, the more complicated and more expensive the factory.

There was a time when almost every American semiconductor company built and maintained their own factories. But today, a new smelter can cost over $10 billion to build. Only the biggest companies can afford this kind of investment. Instead, the majority of semiconductor companies send their designs to independent foundries for manufacturing. Taiwan Semiconductor Manufacturing Co. and GlobalFoundries, headquartered in New York, are two examples of multinational foundries that manufacture chips for other companies. They have the expertise and economies of scale to invest in the hugely expensive technology needed to produce next-generation semiconductors.

Ironically, while the transistor and the semiconductor chip were invented in the United States, there are currently no state-of-the-art semiconductor foundries on American soil. The United States has been here before in the 1980s, when it was feared that Japan would dominate the global memory market. But with the recently passed CHIPS Act, Congress has provided the incentives and opportunities for next-generation semiconductors to be made in the United States.

Maybe your next iPhone’s chips will be “designed by Apple in California, made in the USA.”

Trevor Thornton is a professor of electrical engineering at Arizona State University.