Using Less Helium In Semiconductor Manufacturing

Helium gas is increasingly in short supply. While consumers may be most familiar with it for use in filling balloons, it is used much more heavily in a variety of industrial processes – including semiconductor fabrication. As a result of supply concerns, many companies, including Lam, are looking for ways to reduce their helium usage.

The making of a semiconductor chip involves a wide variety of materials. Some of them, like silicon, are obvious and end up in the final product. Others are not so obvious and may be used behind the scenes in a way that does not incorporate them into the chip. Helium is one of the latter, being used, among other things, for cooling.

Helium is the second-smallest atom in nature, behind only hydrogen. It is a noble gas, meaning that it does not chemically react with any other substance. It liquefies at a chilly -268.9°C (or -452°F). Its boiling and freezing points are lower than those of any other known substances. It also has the highest thermal conductivity – its ability to carry heat away – of any gas except hydrogen.

Like with many other materials, there are two ways to obtain helium: either extract it from nature or synthesize it in a laboratory. Helium can only be extracted since synthesis costs too much. Recycling helium is under discussion, but it is not actively used yet. That means that, when helium is discarded after use, it becomes unavailable for later use.

Finding helium

There is only one practical source of helium: natural-gas deposits. Helium is produced in the earth as a result of the radioactive decay of elements like uranium. That helium collects in underground pockets, and those pockets can often be found adjacent to natural-gas deposits. While there is also helium in the air, it costs 10,000 times as much to reclaim. Therefore, helium released into the environment after use cannot currently be reused or recycled.

While not every deposit of natural gas will have an appreciable amount of helium, many do. In general, 0.3% helium content is the threshold for commercial viability. For those gas fields, helium is separated from the natural gas as the gas is extracted.

Few countries produce helium: US, Canada, Qatar, Algeria, Poland, Russia, and Australia. Within those seven countries, there are fewer than 20 refineries that segregate helium. As that helium is extracted, and as the natural gas supply is exhausted, decreasing amounts of helium will be produced – giving rise to the current concerns about helium’s sustainability over the long term.

As the supply of helium has started to dwindle, helium has become a strategic material, resulting in a concerted focus in industry and government on how and where it should be used in the future. The market is already reacting, with prices having doubled in the last decade. Short-term price spikes and shortages are much more common than in the past, giving rise to the possibility of government regulation.

This is a challenge for manufacturing operations that need to have a steady, predictable source of inputs. Companies are looking for ways to reduce helium from their production processes wherever possible.

Focusing on helium reduction

Lam is working to reduce reliance on helium, which is used for cooling in some equipment. The challenge is to do so without disrupting production of the equipment and the high-volume products built with that equipment.

The challenge is that nothing else (besides ultra-reactive hydrogen) has thermal conductivity as high as helium. That means any practical replacement will pull heat away more slowly. If that heat transfer is too slow, then the cooling steps within the manufacturing process might have to be lengthened. That would increase the overall production time, reducing throughput.

Efforts to date have saved customers a significant amount of helium per wafer produced. But there is more that can be done. As helium alternatives are identified,  customers are expected to save money as helium prices climb. And it will be another big step in the ongoing process of making semiconductor manufacturing more sustainable in the long term.