7nm IC Technology Trends And Challenges (Part 2 of 2)

By V.P. Sampath

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In hybrid metrology, chipmakers use a mix and match of several different tool technologies and then combine data from each. Hybrid metrology, however, is still in developing stage. Fortunately, this silicon alternative does not have any major physical flaw like most other materials.

Silicene and germanene, for example, degrade within a few minutes or hours, while graphene is not suitable for all transistor types and is still extremely challenging to use in the production of integrated circuits due to fragility of its structure. InGaAs and InP based devices can be manufactured using existing techniques in combination with silicon.

The main issue remains to be yield and cost. Beyond 14nm, as we move to 10nm and 7nm, a new fin material will be required—probably silicon-germanium (SiGe), or perhaps just pure germanium. SiGe and Ge have higher electron mobility than Si, allowing for lower voltages and, thus, reducing power consumption, tunneling and leakage.

SiGe has been used in commercial CMOS fabrication since the late 1980s, too, so switching from silicon would not be too painful. The primary reason that we have been using silicon for so long is that the entire industry is based on silicon. The amount of time, money and R&D that would be required to deploy new machines for handling new materials that we know relatively little about would be astronomical.

SiGe would take us to 7nm, but after that we are probably looking at a new transistor structure. Just as FinFET created a larger surface area, mitigating the effects of quantum tunneling, both gate-all-around FETs and vertical tunneling FETs would again allow for shorter gates and lower voltages.

Gate-all-around FET essentially consists of nanowire source and drains, surrounded by a gate. A vertical tunneling FET is similar in a way that it uses nanowires, but the actual method of operation is very different from conventional FETs. TFETs allow for lower operating voltage.

Another option is a somewhat conventional FinFET, but with fin constructed out of III-V semiconductors such as gallium-arsenide (GaAs), which again have higher electron mobility than silicon. There may be better gains to be had from moving sideways, to materials and architectures that can operate at faster frequencies and with more parallelism, rather than brute-forcing the continuation of Moore’s law.

Meaning, the pitch or distance between major features on the chip are still scaling at an expected rate. Reduction in distance between fins, the raised channels behind the name FinFETs, is right on target (0.70x), the distance between gates on top fell just short (0.78x), but the interconnects scaled further than expected (0.65x), thanks in part to the introduction of a new feature, airgaps, that reduces cross-talk between interconnects spaced so closely together. The result is that overall logic area scaling continues.

IP reuse and foundry business

All semiconductor companies develop intellectual property (IP) that they use in their own products or licence to others. For example, 3G and 4G technologies are not just for smartphones and tablets. Development of IP also helps semfab with development partners and with its growing foundry business.

Today, these customers are bringing their own designs using their IP, supplemented with technology, but eventually plan to offer their own IP to customers. As semiconductor manufacturing grows more difficult and expensive, and the number of players dwindles (from 18 a decade ago to just four today in advanced logic), manufacturing edge grows more compelling to other companies.

Enterprise IT hardware is still big and important, but other customers include Cloud service providers, telcos and technical computing. Growth drivers are Cloud architectures, software-defined networks and network-functions virtualisation for communications, high-performance computing and, of course, Big Data and analytics.

And it is getting an increasing share of its revenues from other data centre technologies including storage controllers and Ethernet switches, silicon photonics to replace fibre and copper, fabrics and switches and communications gear. The Internet of Things (IoT), software and services and memory sometimes get lost in the shuffle, but each is on track for more than US$ 2 billion in sales this year.

Although gadgets like MICA bracelet, Basis Peak smartwatch and SMS audio smart earbuds get lots of press, the IoT business is growing quickly due to applications such as retail, automotive and manufacturing.

The software business is growing more strategic and Intel has said, it believes that mobile devices based on its silicon will be the first—other than Nexus-branded ones—to get Android 5.0 Lollipop update.

The memory business, a joint venture with Micron, is shifting from selling memory chips to developing clients and enterprise SSDs, which are increasingly important to close the widening performance gap between CPUs and hard drive based storage.

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