What is the technology behind the manufacturing of a semiconductor chip? | Explained

For representative purposes.

For representative purposes. | Photo credit: iStockfoto

The story so far: Semiconductor chip manufacturing capabilities are currently limited to very few regions in the world. With supply chain disruptions during the pandemic and recent geopolitical tensions, many companies and countries, including India, have realized the importance of investing in chip manufacturing infrastructure. TATA Group has partnered with Taiwan’s Powerchip Semiconductor Manufacturing Corporation (PSMC) to set up a 300mm wafer manufacturing plant in Gujarat. It will launch its first 28nm chip in 2026. The Government of India also recently approved two assembly and testing plants in Gujarat and Assam.

What is a semiconductor chip? How is this made?

A semiconductor has properties between a conductor (which conducts electricity) and an insulator (which does not). In its purest form, a semiconductor is a very weak conductor of electricity. However, its electrical properties can be changed by adding small amounts of certain substances called “dopants.” By taking a pure semiconductor and carefully injecting certain parts with specific dopants, complex circuits can be “printed” onto the semiconductor.

Also read: The need to review a semiconductor schematic.

The process is roughly analogous to creating an intricate piece of art on paper or a wall, using a bunch of stencils and spray paints of different colors. The stencils are called “masks” in the industry and the paint is analogous to the dopant.

What is a transistor?

The transistor, one of the first electronic components built using a semiconductor, is an extremely versatile device. In its most popular form, it can function as an electronic switch. A typical semiconductor chip may have millions or billions of these interconnected switches that work together to perform various logical and computational operations.

A transistor can also function as an amplifier (to amplify the weak signal your cell phone receives) and is an integral part of the circuits that generate and process high-frequency signals (such as those required in wireless communication technologies). Today, all of these different avatars of the transistor are typically packaged on a single semiconductor chip (like the WiFi chip in your mobile phone).

The transistor demonstrated how a single device could be built from a piece of semiconductor. The next step was to “print” multiple devices onto a single piece of semiconductor to create complete circuits. Both advances laid the foundations for the semiconductor revolution and have been duly recognized with the Nobel Prizes (in 1956 and 2000).

What is manufacturing technology?

Technology has progressed at a relentless pace since the semiconductor chip was first conceptualized more than six decades ago. New manufacturing technologies have been introduced at a regular pace. The level of miniaturization of semiconductors has increased by orders of magnitude. Continuing with the stencil analogy, this is mainly because stencils can engrave smaller, more intricate patterns. There have been equally impressive gains in the switching capacity of transistors. They are capable of turning on and off faster (more calculations per second) and with lower power consumption (longer battery life and lower heat dissipation).

The industry has used labels such as ’45nm’, ’28nm’ and ’16nm’ to introduce each new manufacturing technology. ‘nm’ is short for nanometer and refers to an extremely small unit of length equivalent to one billionth of a meter. These numbers convey the level of miniaturization that can be achieved using a particular technology (so smaller is better). Although not always exact, this number can be considered to represent the dimensions of a single transistor. While electronic circuits have traditionally been laid out flat on the semiconductor, researchers are increasingly seeking to capitalize on the third dimension (height). As the length and width of a transistor switch decreases, increasing its height can help ensure reliable performance. Stacking entire circuits on top of each other is another way to further reduce the size of semiconductor chips.

What is known as a wafer?

A semiconductor chip is manufactured much like a postage stamp. A sheet of stamps is printed on a sheet of paper and then each individual stamp is cut out. Similarly, a series (typically between 300 and 400) of chips are printed on a circular piece of semiconductor (called a wafer in industrial parlance). It is then diced to create individual chips. A larger wafer size allows more chips to be printed on a single wafer, making chip production faster and cheaper. Wafer sizes used in industry have been increasing steadily. The current state of the art is 300 mm, which is approximately 12 inches (this refers to the diameter of the wafer). Efforts are underway to move to a 450mm wafer size. While moving to a larger wafer size has its technical challenges and capital expenditures, it has proven to be economical in the long term.

Once the wafer is cut into pieces, each individual piece must be wrapped in a protective sleeve. Small cables must be run from the device to the edge of the package. Some of these cables supply power, while others are used to input and read signals and data. A chip also needs to be tested (this includes checking its functionality and stress testing (subjecting the chip to high temperatures and voltages)) to ensure reliability over its lifetime. All of this is done in an assembly and testing plant.

Also read: Explained | Mapping India’s chip design ecosystem

What is India’s semiconductor ecosystem like?

India has had a thriving chip design industry since the 1990s. Thanks to the magic of computer-aided design, it is possible to design a semiconductor chip entirely using software. The process of specifying the functionality of a chip, translating this functionality into electronic circuits, validating the circuits, and optimizing speed, power consumption, and size can be performed by a team of trained engineers sitting at their desks. The final design is summarized in a file and sent to a manufacturing plant for manufacturing. It’s a bit like designing an entire graphic novel on your laptop and then sending the pdf to your editor to print.

India’s foray into semiconductor manufacturing will benefit from the existing ecosystem for chip design, driven by a steady supply of electronics and computer engineers. With semiconductor manufacturing being an essentially interdisciplinary endeavor, it could present opportunities for a broader range of professionals, such as process and control engineers, data scientists, materials scientists, physicists and chemical engineers, to contribute significantly to this industry. .

The author works with Texas Instruments.

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