The City In The Tower: 3D ICs Transform The Electronics System Landscape

By Keith Felton and Todd Burkholder

The time of 3D integrated circuits (3D ICs) is here, and they will revolutionize the semiconductor industry and effect a watershed in the nature of electronics products that can be designed and manufactured. Yet again—as with personal computers, the internet, and smart phones—our increasingly digital world will never be the same.

3D IC architectures make this possible in part by pushing Moore’s Law (the doubling of transistor counts in ICs every two years) over the next threshold. Instead of stalling out, as many experts predicted, Moore’s Law will be revitalized and turbocharged.

Thus, to meet ongoing global demand for ICs that deliver more performance and lower power consumption within ever smaller footprints, IC designs increasingly feature sophisticated packaging techniques such as 2.5D and 3D configurations. These techniques combine one or more ICs of different functionality with increased I/O and circuit density.

So what is this 3D IC stuff? First, let’s illustrate with a metaphor.

Imagine a towering mixed-used building comprising housing, offices, services, shopping, grocers, gyms, libraries, shipping depots, and more.

By connecting all these varied businesses and resources in a single space, people and commerce enjoy faster, more efficient movement as they go about their daily activities. Going from place to place requires little power—at most an elevator, or just take the stairs—and both communication and interactions are immediate and direct. Vast and varied amounts of information and goods are available right on site. Because real estate and greenspace must be preserved and intelligently utilized, we build up, creating vertical landscapes rather than sprawling development. Yet our efficient, convenient, and environmentally friendly “city” in a tower occupies a lateral space as well, which includes greenspaces, parks, athletic fields, bike paths, water features, power plants, warehouses, essential infrastructure, and the requisite transportation nodes and connections to both internal and external locations — importantly, the use of horizontal space is optimized, more compact, and efficient than that of vast cities that carpet vast swaths of land.

Like our gleaming 3D city in a tower, 3D ICs are distinguished by the stacking of multiple layers of silicon on top of each other. This allows for the creation of more powerful and complex chips that can be used in a wider range of applications. There are several reasons why 3D ICs are such an area of interest today.

First, the traditional method of manufacturing ICs—called monolithic 2D ICs or planar ICs—is reaching its limits. As transistors get smaller and smaller, it becomes increasingly difficult to create reliable and efficient monolithic 2D ICs. 3D ICs offer a way to overcome these limitations and continue to shrink the size of transistors while also increasing the number of transistors that can be placed on a single chip. Thus, propelling Moore’s Law into the future.

Second, 3D ICs improve the performance of chips. By stacking multiple layers of silicon on top of each other, 3D ICs reduce the distance that signals travel, which leads to faster performance. Additionally, 3D ICs can be used to create chips with multiple cores, also improving performance.

Third, 3D ICs help reduce the power consumption of chips. 3D ICs use less power, as they need only push the signals over a much shorter distance, but they still generate heat, which is directly passed on to neighboring ICs. This can create challenges if neighboring components are sensitive to heat, such as memory. So thermal management of 3D ICs and heterogeneously integrated devices is a major factor that must be considered at the start of a design. On the plus side, 3D ICs can be used to create chips with more efficient power management features, reducing power consumption even further.

Overall, 3D ICs offer many advantages over traditional monolithic 2D or planar ICs.

• Increased performance: As mentioned, 3D ICs offer increased performance due to the shorter distances between components and the ability to integrate multiple technologies. This leads to faster and more responsive devices, as well as the ability to handle more complex tasks.
• Reduced size and weight: 3D ICs offer reduced size and weight due to the ability to stack multiple layers of components on top of each other. This leads to smaller, more portable devices, as well as devices that are better suited for use in cramped or difficult-to-access spaces.
• Improved power efficiency: 3D ICs offer improved power efficiency, also due to the shorter distances between components and the ability to integrate different technologies. This can produce devices that last longer on a single charge, as well as devices that produce less heat, which can be important for safety and reliability requirements.
• Increased flexibility: 3D ICs offer increased flexibility due to the ability to integrate multiple different technologies on a single chip. This leads to devices that are more versatile and that can be used for a wider range of tasks.

These advantages are particularly interesting for a number of applications where early adoption is either already occurring or will happen in the near future.

• High-performance computing (HPC): The first adopters have been in HPC. 3D ICs are employed to create HPC chips used in applications such as artificial intelligence (AI), machine learning, and big data analytics.
• Wearable devices: 3D IC chips allow the production of smaller, more powerful wearable devices such as smartwatches, fitness trackers, and augmented reality (AR) headsets.
• Automotive: The integration of different technologies and their ability to scale makes 3D IC ideal for retargeting designs for different markets and applications such as autonomous driving and advanced driver-assistance systems (ADAS). 3D ICs are also attractive because they offer a lower NRE and a broader ecosystem of suppliers, supporting a more robust and resilient supply chain.
• Medical devices: 3D IC can also be used to create smaller, more powerful medical devices such as pacemakers, insulin pumps, and hearing aids.

These are just a few of the applications for 3D ICs. As the technology continues to develop, we can expect to see even more innovative and groundbreaking applications for 3D ICs in the years to come.

3D IC architecture is an emerging technology with the potential to revolutionize the electronics industry. By offering increased performance, reduced size and weight, improved power efficiency, and increased flexibility, 3D IC enables the development of new and innovative electronics products that meet the needs of a wide range of users and applications.

Stay tuned. By the time this revolution is televised, it will already be here, and you will no longer have the advantage to lead the pack of competitors, regardless of your business.

Todd Burkholder is a senior writer at Siemens Digital Industries Software.