For as long as we’ve been using semiconductors there’s been one material that’s held the crown: silicon. Being one of the most abundant elements on Earth its semiconductor properties made it perfectly suited to mass manufacture and nearly all of the world’s electronics contain a silicon brain within them. Silicon isn’t the only material capable of performing this function, indeed there’s a whole smorgasbord of other semiconductors that are used for specific applications, however the amount of research poured into silicon means few of them are as mature as it is. However with our manufacturing processes shrinking we’re fast approaching the limit of what silicon, in its current form, is capable of and that may pave the way for a new contender for the semiconductor crown.
The road to the current 14nm manufacturing process has been a bumpy one, as the heavily delayed release of Intel’s Broadwell can attest to. Mostly this was due to the low yields that Intel was getting with the process, which is typical for die shrinks, however solving the issue proved to be more difficult than they had originally thought. This is likely due to the challenges Intel faced with making their FinFET technology work at the smaller scale as they had only just introduced it in the previous 22nm generation of CPUs. This process will likely still work down at the 10nm level (as Samsung has just proven today) but beyond that there’s going to need to be a fundamental shift in order for the die shrinks to continue.
For this Intel has alluded to new materials which, keen observers have pointed out, won’t be silicon.
The type of material that’s a likely candidate to replace silicon is something called Indium Gallium Arsenide (InGaAs). They’ve long been used in photodetectors and high frequency applications like microwave and millimeter wave applications. Transistors made from this substrate are called High-Electron Mobility Transistors which, in simpler terms, means that they can be made smaller, switch faster and more packed into a certain size. Whilst the foundries might not yet be able to create these kinds of transistors at scale the fact that they’ve been manufactured at some scale for decades now makes them a viable alternative rather than some of the other, more exotic materials.
There is potential for silicon to hang around for another die shrink or two if Extreme Ultraviolet (EUV) lithography takes off however that method has been plagued with developmental issues for some time now. The change between UV lithography and EUV isn’t a trivial one as EUV can’t be made into a laser and needs mirrors to be directed since most materials will simply absorb the EUV light. Couple that with the rather large difficulty in generating EUV light in the first place (it’s rather inefficient) and it makes looking at new substrates much more appealing. Still if TSMC, Intel or Samsung can figure it out then there’d be a bit more headroom for silicon, although maybe not enough to offset the investment cost.
Whatever direction the semiconductor industry takes one thing is very clear: they all have plans that extend far beyond the current short term to ensure that we can keep up the rapid pace of technological development that we’ve enjoyed for the past half century. I can’t tell you how many times I’ve heard others scream that the next die shrink would be our last, only to see some incredibly innovative solutions to come out soon after. The transition to InGaAs or EUV shows that we’re prepared for at least the next decade and I’m sure before we hit the limit of that tech we’ll be seeing the next novel innovation that will continue to power us forward.