To beat the heat that limits the performance of the computers and other gadgets we use, Silicon Valley is looking to some surprising materials. Chip companies large and small are experimenting with chunks of synthetic diamond, chunks of ultra-pure glass, or even an obscure material that has only recently been synthesized in sufficient quantities to test its properties.

Heat is an old engineering problem. Thomas Edison’s first practical light bulb was successful largely because he did not allow it to burn out quickly. Conventional gas engines require oil and coolant to prevent failure, while nuclear reactors require cooling to prevent failure.

If you’ve got an old enough laptop — one that can get uncomfortably hot on your feet — you’re already well aware of the main obstacle to speeding up computers.

“The hard limit of chip performance is the maximum temperature of the chip,” says Andy Bechtolsheim, who in 1982 founded Sun Microsystems and was the company’s chief hardware designer. Silicon chips can’t operate above 221 degrees Fahrenheit or they become unreliable.To achieve higher speeds without failure, chipmakers aim to dissipate heat, or move it away from the source, as quickly as possible.

The heat is on

Today’s high-performance chips can use about 100 watts per square centimeter, says Gang Chen, director of the Massachusetts Institute of Technology’s Nanoengineering Laboratory. Energy chips used for computing are ultimately converted into heat, “and that heat has to come out,” he adds.

This is a particularly acute problem in data centers used to develop the latest, greatest, and largest AI models. From one generation of these models to the next, the required computing power increases by an average of 10 times. Getting to the next generation will require every trick in the book, and alternative chip substrates like diamond can help, Bechtolsheim says.

Similar challenges face those who design the power-converting electronics in electric vehicles, which are increasingly manufactured in the same way as chips and from related materials. This is as much about reducing the size of these electronics as it is about squeezing out even more power. This is something else that could help diamonds, as shrinking the EV’s all-important power converter depends on dissipating the heat it generates more efficiently.

One of the largest diamonds in the world

Diamond is the best conductor of heat known to mankind. (Cool parlor trick: It’s so good you can cut through a block of ice with just your body heat.) But just yet, you can’t make chips out of it. So the next best thing is to make a regular chip, shave off most of the inactive silicon on top of the active chip tips, and bond what’s left with a single perfect diamond crystal.

At the diamond foundry, which has a lab in Silicon Valley and a first factory in Wenatchee, Washington, engineers have created what the company says is the world’s largest diamond, at least in diameter. Diamond Foundry uses technology it acquired in 2022 when it acquired the German firm Augsburg Diamond Technology, also known as Audiatec. Four-inch-diameter, less than 3-millimeter-thick synthetic diamond wafers grown in the reactor can be bonded to silicon chips, allowing the chips to quickly dissipate heat. To date, the company has produced hundreds of these largest plates. This means the chips can run at least twice their rated speed, called clock speed, without failure, says Martin Roscheisen, the company’s CEO. Using this method on one of Nvidia’s most powerful chips, Diamond Foundry engineers were able to increase the normal speed up to three times under laboratory conditions.

Roscheisen says his company is in talks with most of the world’s largest chipmakers, as well as several defense contractors and electric vehicle manufacturers, to make the chips and electronics they make run faster, shrink into a smaller volume, or so.

A key factor in all of this is the falling cost of synthesizing these diamonds. These wafers are comparable in cost to those made from silicon carbide, which is often used in power electronics, Roscheisen says.

Although the Diamond Foundry claims to be the first to create large slabs of monocrystalline diamonds, there is another type of diamond that is easier to synthesize, called polycrystalline. Saxonburg, Pa., Coherent, founded in 1971. in order to create materials for lasers, offers this type of polycrystalline plates. Other companies, such as synthetic diamond company Element Six, part of the De Beers Group, offer even larger diamonds that can be placed between chips and traditional coolers.

Ultra pure glass

Intel is working to put the chips on a glass substrate, which could have many advantages, including the ability to keep larger and larger megachips intact as they increase in size and number of chips in a single integrated package.

In this context, the glass doesn’t help dissipate heat, but it does help keep the chip intact as it grows and has to deal with more power being pumped through it and heat being removed from it.

“These AI systems are achieving kilowatts of heat per package,” says Rahul Manepalli, an Intel fellow working on next-generation chip packaging technologies.

That’s about as much power as a hair dryer coming from a chip pack that’s about 4 inches square.

Adding a glass substrate gives these giant, power-hungry chips extra structural support. Because glass can accommodate a higher density of new types of connections between chips, it can allow them to talk to each other at much higher speeds without using as much power.

Intel will introduce glass-based chips in the second half of this decade, Manepalli says, and has already demonstrated the technology’s effectiveness in the lab.

Avoid silicon altogether

In the much more distant future, scientists and engineers envision a day when we can completely replace silicon in microchips. One alternative candidate is boron arsenide, which scientists including Chen recently confirmed is the third best material in the world in terms of its ability to transfer heat. One big difference between diamond and boron arsenide is that while diamond is an insulator, boron arsenide is a semiconductor, like silicon. This means it can be used to make actual chips. Such chips would have features unheard of in current chips, as they would be able to run much, much faster because they would be able to dissipate the heat they produce in the process much faster.

These chips would also have another attractive feature. Boron arsenide crystals move well around positively charged quasi-particles known as “holes” — think of them as materials that can have an electron but don’t. not widely used today.

Someday, computer chips may be made up of a shiny and incredible sandwich—glass on top for high-speed communication, a three-dimensional stack of silicon layers in the middle for processing, and a diamond wafer underneath to dissipate all the heat. says Bechtolsheim.