More and more machines in our lives, from computers to small medical devices implanted in the human body, are built around microprocessors, which are getting smaller, yet more powerful all the time. Laszlo Dosa reports on the work of an engineer who is making them even more so.
At the Florida Institute of Technology in Melbourne, Florida, Peruvian-born Dr. Hector Gutierrez is studying magnetic levitation to design ever-smaller microprocessors. They, in turn, will lead to much smaller, yet much more powerful computers. "Magnetic levitation is a physical principle that allows us to move objects relative to each other without contact, based on the attractive or repulsive forces of electromagnets," he says.
An electromagnet is a piece of metal with a coil wrapped around it. When a current is passed through the coil, the metal becomes magnetic, attracts other pieces of magnetic material. Dr. Gutiérrez uses the electromagnet to design and build an ultra-high precision machine to "cook" semiconductors that are at the heart of the microprocessor. "Semiconductors are built on a silicone wafer substrate and cooked in an oven following a series of etching and chemical deposition processes. This is a very involved, very complex process and the machine I am building addresses only one aspect of this complex process, the overlay of the lithography mask," he says.
Dr. Gutiérrez offers a simple analogy, that of painting a car, to explain the complicated procedure: "You want to paint letters on the side. So put a mask and then you run your paint," he says. "Now, let's say you want to put a second edge around whatever you have painted on this door. So you need a second mask. And the second mask must be very well aligned with the first one for you to get a good result."
If the secret of a good paint job is to have the succession of perfectly aligned masks, it is even more important when manufacturing microscopically small semiconductors. Letters painted on a car may be several centimeters tall, while the etchings on semiconductors are measured in nanometers. One nanometer equals 1,000-millionth of a meter. "At the moment, the machines are limited by the complex microscopic phenomenon of friction. If you use a machine where the components are in contact, it is extremely hard to go beyond the sub-micron (less than one-millionth of a meter) range with consistency and accuracy and repeatability," he says. "The next generation of lithography machines will have to get away from this complex microscopic phenomenon by having machines that float in the air and therefore are perfectly repeatable and highly accurate."
The current generation of semiconductors is on the order of 340 nanometers, less than 1/20th the size of a red blood cell. Dr. Gutiérrez hopes to develop a machine that will use magnetic levitation to reduce them to 100 or 50 nanometers.
If the work is successful, the impact will be very broad because the capacity to build much smaller semiconductors will lead to the creation of more powerful products. Today, a computer smaller than a telephone directory is much more powerful than computers 50 years ago that filled several large rooms. Dr. Gutiérrez's magnetic levitation technique may lead to even more powerful computers the size of a matchbox.