MIT Scientists Grow Atomically Thin Transistors on Computer Chips to Make Them More Denser

MIT Scientists Grow Atomically Thin Transistors on Computer Chips

A new technology developed, MIT (Massachusetts Institute of Technology) scientists grow atomically thin transistors on computer chips allows for the growth of ultrathin 2D materials, each only about three atoms in thickness, directly on top of a fully fabricated silicon chip. This technology enables the creation of more powerful computer chips that are better suited for emerging AI applications, such as chatbots that generate natural human language. Let's explore this game-changing technology with The Mechatronics Blog.

The primary challenge with growing 2D materials directly onto a silicon chip is the high temperature required, which can damage the chip. The researchers overcame this challenge by developing a low-temperature growth process that does not damage the chip. This technology allows 2D semiconductor transistors to deposit on the top of the Silicon Wafer.

Previous methods for growing 2D materials involved growing them elsewhere and then transferring them onto a chip or a wafer which caused imperfections that creates issues in final devices and circuits. And also, transferring material to the wafer is extremely difficult. But this new process can grow a smooth and highly uniform layer across an entire 8-inch wafer.

The new technology significantly reduces the time it takes to grow these materials. Previous methods require more than a day to grow a single layer of 2D material but this new technology can grow it in less than an hour over the 8-inch wafer. This kind of fast and uniform technology helps researchers to successfully integrate a 2D material layer onto much larger surfaces.

MIT researchers choose 2D material as Molybdenum Disulfide because of its flexibility, transparency, and strong electronic and photonic properties which makes it suitable for semiconductor transistors. Molybdenum Disulfide is three atoms thick as one atom layer of molybdenum, between that two atoms of sulfide.

Molybdenum Disulfide (MoS2) Structure (img credit-ossila.com)

Applying thin films of molybdenum disulfide on the surface of the wafer in precise uniformity is achieved by the process known as metal-organic chemical vapor deposition (MOCVD). However, decomposing the precursors required for this process requires temperatures above 550 degrees Celsius, while silicon circuits start to degrade when temperatures surpass 400 degrees.

To overcome this challenge, the researchers designed and built an entirely new furnace for the MOCVD process that contains two chambers one is the low temperature in front of the wafer and one other is a high-temperature chamber in the back. Vaporized forms of molybdenum and sulfur are pumped into the Furnace. As of property, the molybdenum stays in the low-temperature region, where the temperature is kept below 400 degrees Celsius,  and on the other hand, sulfur precursor flows through into the high-temperature region, where it decomposes. Then sulfur comes back into the low-temperature chamber where the chemical reaction occurs to deposit molybdenum disulfide on the surface of the wafer.

One issue with this process is that sulfur causes the metals typically used in silicon circuits, such as aluminum or copper, to sulfurize, which can lead to performance issues. To solve this problem, the researchers added a protective layer of titanium between the silicon and the 2D material. This layer prevented the sulfur from reaching the aluminum or copper and causing damage.

“Using 2D materials is a powerful way to increase the density of an integrated circuit. What we are doing is like constructing a multistory building. If you have only one floor, which is the conventional case, it won’t hold many people. But with more floors, the building will hold more people that can enable amazing new things. Thanks to the heterogeneous integration we are working on, we have silicon as the first floor and then we can have many floors of 2D materials directly integrated on top” says Jiadi Zhu, ( electrical engineering and computer science graduate student and co-lead author of a paper on this new technique ).

This new technology developed by MIT researchers has the potential to revolutionize the computer chip industry. The ability to grow ultrathin 2D materials directly on top of a silicon chip opens up a range of new possibilities for emerging AI applications and other advanced technologies. This new process reduces the time it takes to grow these materials, produces highly uniform layers, and enables the integration of 2D material layers onto much larger surfaces than previously possible.