Supporting the Future of Semiconductors from Materials

Supporting the Future of Semiconductors from Materials

In today’s world, where we are surrounded by digital devices, most people have heard of semiconductors at least once. They are not only found in computers and smartphones but also in household appliances, automobiles, trains, and almost every machine around us. To create a more prosperous society, semiconductor performance must continue to improve in the future. However, as the amount of information increases, so does energy consumption. In recent years, the need for energy-efficient and highly efficient semiconductors has become an urgent issue. Professor Kentarou Sawano of the Nanotechnology and Electronics Research Center at the Institute of Science and Technology is dedicated to researching the development of higher-performance semiconductors.

A crucial material in semiconductor manufacturing is the thin, disk-shaped silicon wafer. As the name suggests, it is made of silicon, the second most abundant element on Earth after oxygen. Silicon is easily obtainable, easy to process, chemically stable, and safe to use in various environments. The manufacturing process involves refining quartz, creating single-crystal silicon, and undergoing several processing stages to produce silicon wafers. These wafers serve as the substrate on which circuits are written to create integrated circuits (ICs). “Our research aims to improve the fundamental material of semiconductors to make them more efficient.”

A single IC chip, approximately one centimeter square, contains more than 10 billion tiny transistors, each about a few tens of nanometers in size. Transistors act as switches that control the flow of electricity, enabling digital processing of 0s and 1s. Connecting multiple transistors allows vast amounts of data to be processed, but it also increases electrical wiring, leading to greater heat generation. Data centers, which IT companies worldwide are rapidly constructing, consume vast amounts of electricity due to the semiconductors inside servers, posing a significant problem. “The amount of information will only continue to grow. It is estimated that by 2030, data centers will consume 10% of the world’s total power generation. If we do nothing, technological development itself will reach its limits, and the growth of society could come to a halt.”

A potential solution to this issue is chip-level optical wiring, which replaces electrical signal transmission with optical transmission. Since light does not generate heat, energy consumption can be significantly reduced. The development of optical integrated circuits, known as silicon photonics, is underway worldwide. If successfully implemented, it will have a major impact on society. “We can already convert optical signals into electrical signals and create optical pathways. However, the light source, the laser, has not yet been realized. Since silicon itself does not emit light, we are working on creating a thin film of germanium on silicon wafers to bring this closer to reality.”

Germanium shares similar properties with silicon but allows for better electron mobility, making it highly beneficial as a semiconductor material. Using a germanium substrate would be effective, but germanium is a rare material and not as easily obtainable as silicon. Professor Sawano’s lab has successfully developed a technique for creating large-area germanium wafers, allowing silicon wafers to function as if they were made of germanium. This marks a significant step toward achieving chip-level optical wiring, with practical implementation expected in about ten years. “By melting silicon and germanium at high temperatures, evaporating them, and allowing the atoms to bond, we can grow crystals and form a thin germanium film on silicon. We are also researching how to prevent crystal cracks that occur during this process. The possibility of creating silicon-germanium, an element that lies between silicon and germanium, is quite fascinating.”

Tokyo City University has established a large-scale cleanroom for semiconductor manufacturing, providing one of the best environments among private universities. Around 80 students are conducting research here day and night. Professor Sawano’s research on semiconductors heavily involves hands-on material development. “I have always been fascinated by creating new materials with human ingenuity, which is why I continue this research. Experience plays an important role in manufacturing, and students teaching each other experimental techniques is also crucial. Conducting research in a lively, collaborative environment leads to better results. One advantage of researching in Tokyo is that it attracts many people.”

When asked about his perspective on an ever-expanding information-driven society, Professor Sawano gave an unexpected response: “Many people get overwhelmed by information, and human relationships seem to be weakening. I believe that trust and affection are essential for people.”

Just as new materials are created by human hands, knowledge and experience are passed down in the laboratory, fostering new possibilities. In an era flooded with vast amounts of data, Professor Sawano’s words carry a certain warmth. Technological innovation should not separate people—it should bring them closer together. With this vision, his research laboratory continues to make passionate strides forward.