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What you may not know about GF

Latest update time：2021-06-22

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Despite recent controversies, GlobalFoundries remains a leading foundry in semiconductor manufacturing.

Over the past few years, companies like TSMC, Samsung, and Intel have chased the technology definition of Moore’s Law while ignoring all cost scaling advantages and disagreeing over the use of the term. For this reason, many will incorrectly claim that GlobalFoundries is out of the race for leadership because they stopped development of the 7nm node. Although this is the dominant form of semiconductor leading-edge manufacturing, it is not the only form.

In our view, GlobalFoundries is pushing the frontier of manufacturing in other equally important ways. For example, silicon photonics, the use of materials such as silicon nitride and gallium nitride for wired and wireless communications, 3D integration, heterogeneous integration, and fully depleted silicon-on-insulator technology (FD-SOI) are all treasure troves for GlobalFoundries to look to in the future.

GlobalFoundries offers the highest volume and most advanced FD-SOI platform with its 22FDX and upcoming 12FDX process technologies. They will also be a leader in 5G and 6G radio applications with these nodes and are collaborating with Raytheon Technologies on GaN-on-Silicon.

GlobalFoundries demonstrated 3D manufacturing with the highest level of integration in the industry. Working with Arm, GlobalFoundries publicly demonstrated hybrid bonding of multiple die with tighter pitch than any other competitor’s logic node. They used 5.76um copper through silicon vias (TSVs) and could maintain the same clock domain on both die. These chiplets are completely transparent and act as a single die despite being multiple chips.

TSMC is driving hybrid bonding into volume production with 9um TSVs, stacking SRAM on AMD CPUs. TSMC plans to launch 6um and 4.5um in the next few years. Intel only discusses <10um pitch for its 3rd generation Foveros technology. Sony, which pioneered this technology in CMOS image sensors, is currently at 5um. In addition, GlobalFoundries even has 3D stacked silicon photonic chips with standard logic chips, which is something that no other company in the industry can achieve.

Lightmatter is a silicon photonics AI startup that has attracted the industry at the previous Hot Chips conference. They use GlobalFoundries' production lines for manufacturing - GlobalFoundries foundry 90WG process for silicon photonics computing core production, and they also use GlobalFoundries' standard 14nm foundry process for control ASIC production including stacked SRAM. Lightmatter then uses GlobalFoundries' leading 3D technology and capabilities in heterogeneous integration to create a tightly integrated and efficient photonics and logic computing stack.

The use of photonic chips enables Lightmatter to achieve multiple orders of magnitude advantages in latency, bandwidth, and power. A small fraction of the power is used to transmit data and perform matrix multiplication calculations, both of which are very large bottlenecks for AI computing.

The photonic core itself is not a static element. Despite being a silicon photonic process, it is highly reconfigurable, in stark contrast to other silicon photonics attempts in the industry. It can quickly reconfigure its weights. Networks can be tweaked or changed together. Despite the reconfigurability, the laser input remains extremely low power. The GlobalFoundries 90WG process node ensures minimal losses as light bounces around the photonic core and compute.

GlobalFoundries currently provides state-of-the-art silicon photonics foundry services using its 90 WG technology. This technology is actively used in data center interconnects, 5G remote radio heads, and telecommunications. Most use 1310nm wavelength light for internal use in data centers, and 1550nm for longer distances. They are rapidly seeing advancements in other areas such as photonic computing, ToF sensors, LiDAR, and aviation.

These emerging areas will be targeted by their growing 45CLO process. The process will not only meet silicon photonics needs in the O-band, but also in the C and L-band. 90WG used up their Fab 9, and 45CLO used up the larger Fab 10. The 45CLO process is also a silicon-on-insulator technology.

The GlobalFoundries 45CLO process is different from other foundry photonic IC processes in two ways. It is the only foundry process capable of C-band, L-band, and O-band. In addition, they can integrate active and passive components on a single chip. Linear drivers, redrivers, and TIAs can now be on the same chip with optical components such as photodetectors and modulators.

GlobalFoudries has various elements supported by public EDA vendors, such as various modulators, waveguides made of silicon or silicon nitride, polarization beam splitters and rotators, passive fiber connections, direct laser connections, and copper pillars and receiver pads. These standardized tools and modules will enable many fabless companies to easily design and build silicon photonic chips to meet the changing market needs.

GlobalFoundries recognized that producing chips using electronics is a completely different skill set than producing chips using photons. Development practices had to be completely restructured and changed. They fully embraced this change while others in the field were splitting their attention in many directions. This unique focus has made GlobalFoundries a frontrunner in emerging cutting-edge applications.

GlobalFoundries has chosen to leverage their expertise in silicon rather than try to completely move the industry to more exotic materials. Silicon is an indirect bandgap material that does not have the same properties as Indium Phosphide in many photonics applications. There are many negatives associated with silicon-based solutions for photonics, such as lasers, modulators, and amplifiers. The benefits of using silicon far outweigh the negatives. GlobalFoundries is leveraging 300mm wafer production technology and the scale of the silicon industry to drive the integration of active and passive components on a single wafer, resulting in significant cost advantages.

In addition to the 45CLO process, GlobalFoundries will also bring differentiated packaging technologies. These technologies enable them to take advantage of heterogeneous 3D integration with classical logic processes, such as the Lightmatter chip shown above. They can bond indium phosphide lasers, saving space, power and cost compared to external lasers. Finally, they offer a passive fiber connection process that slides single optical fibers into etched V-grooves to guide them into waveguides. This allows for a higher fiber count and therefore a higher bandwidth density. In addition to bandwidth density, there are also advantages in integration complexity and cost.

Currently, most silicon photonics are used for optical transceivers, with GlobalFoundries leading the way. 400G technology is being deployed at scale, and early 800G technology is starting to emerge. The surge in data traffic in and around data centers has led to disruptions in intra-rack communications. Currently within data center racks, most communications are currently done over short-distance copper cables. But copper cables can no longer meet the expansion needs, and SiPh-driven fiber is the only way out. In the near future, even chip-to-chip interconnects will need to move to optics, otherwise the percentage of power used for I/O will consume most of the packaging power budget.

The next wave of photonics beyond optical transceivers will be co-packaged optics. The left picture shows a current model with an optical module, and the right picture shows a model with a package. Electronics, optics, and laser components are currently placed far away from the switch ASIC. As we continue to expand bandwidth requirements, this will limit expansion and increase power consumption. Integrating electronics and optics into a single monolithic chip while bringing them closer to the switch ASIC will greatly save power.

Putting it all together, the biggest benefit is that your bandwidth density goes through the roof. The 45CLO process is capable of >0.6Tbps/mm^2. The power per bit is also an order of magnitude better than copper solutions at less than 1pj/bit. GlobalFoundries customers are developing products that can transmit 16 different wavelengths of light over a single fiber through a single monolithic chip. Previously such a complex array would have required dozens of integrated circuits, TIAs, discrete lasers, and separate re-drivers for each wavelength of light. In addition to power consumption and cost, this level of integration also brings a 3 order of magnitude advantage in error rate.

While GlobalFoundries has given up on chasing Moore’s Law, they haven’t stopped being a leading foundry. They continue to push the frontiers of technology in many other ways. While others focus on generational density and power improvements in electronic computing in traditional logic process technologies and ignore them, GlobalFoundries is solving industry-wide scaling problems.

Their fully depleted silicon-on-insulator and gallium nitride-on-silicon technologies are at the forefront of efficient and high-performance radio technology, driving higher performance and withstanding higher thermal and power requirements. Their silicon photonics technology is the beginning of a paradigm shift, changing the core elements of computers and wired communications from electronics to photons. Their 3D and heterogeneous integration expertise allows the combination of conventional logic, low-power FDX, radio optimization, photonics, InP and SiN technologies to be integrated into an innovative solution that leverages the best technologies for the application needs.

Due to this advanced technology, Global Foundries is a leading foundry, beating out other companies like TSMC, Intel, and Samsung.

*Disclaimer: This article is originally written by the author. The content of the article is the author's personal opinion. Semiconductor Industry Observer reprints it only to convey a different point of view. It does not mean that Semiconductor Industry Observer agrees or supports this point of view. If you have any objections, please contact Semiconductor Industry Observer.

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