6G: Key Hardware Technologies and Future Development Roadmap

The evolution of telecommunications continues with each decade, and as 5G becomes widespread, attention is shifting to the next generation: 6G. Promising next-level capabilities compared to next generation, 6G will offer data rates reaching terabits per second (Tbps), microsecond-level latency, and ultra-high level of network reliability. Operating within the terahertz (THz) spectrum, 6G isn’t just about faster connections; it will enable new applications beyond communications, like energy harvesting, advanced sensing, and more.

 

A crucial aspect of 6G is its use of new frequency bands. While 5G operates within the sub-6 GHz spectrum (3.5 to 6 GHz) and the millimeter wave (mmWave) band (24 to 100 GHz), 6G will expand into higher frequencies. The potential spectrum for 6G includes the 7 to 20 GHz range for mobile coverage and broader applications, as well as the W-band (75 to 110 GHz) and D-band (110 to 175 GHz) for access networks and services like Fronthaul and backhaul, collectively known as Xhaul.

 

Although global spectrum allocations have yet to exceed 275 GHz, the range from 275 to 450 GHz is being considered for terrestrial and fixed services, alongside other applications such as radio astronomy and space research. These developments indicate that 6G will utilize frequencies well beyond what current networks use, potentially up to 10 THz, with the telecommunications industry categorizing any application above 100 GHz as part of THz communications.

 

This overview draws from the latest findings in the IDTechEx report, “6G Market 2023-2043: Technology, Trends, Forecasts, and Players“, which offers a detailed analysis of key 6G technologies and commercial outlook for the emerging 6G landscape. The report highlights the critical aspects of frequency spectrum, technological advancements, and the global roadmap that will shape the future of 6G. IDTechEx has also released several in-depth reports focused on essential hardware technologies that will drive 6G communications. These include “Antenna in Package (AiP) for 5G and 6G 2024-2034: Technologies, Trends, Markets“, and “Low-Loss Materials for 5G and 6G 2024-2034: Markets, Trends, Forecasts“. This article will also highlight some key findings from each of these reports.

 

 

Terahertz signals are easily absorbed by the atmosphere, leading to rapid signal decay, and are highly susceptible to interference from physical barriers like buildings and trees. These issues are especially problematic in dense urban environments, where maintaining consistent connectivity is critical.

 

To address these challenges, enhancing the link budget—by increasing both antenna gain and power amplifier (PA) gain—is essential for improving signal strength and range. The following sections will explore strategies for optimizing both antenna (from material and packaging design perspectives) and PA design to overcome these hurdles.

 

Additionally, high-frequency communication, such as 5G mmWave and upcoming 6G networks, offer immense data transfer speeds and low latency but struggle with propagation over long distances and penetration through obstacles like buildings and foliage. Maintaining signal strength and quality becomes crucial for realizing the full potential of these advanced wireless technologies.

 

RIS has emerged as a pivotal technology for overcoming these challenges. By strategically deploying RIS, it becomes possible to redirect signals around obstacles, effectively eliminating coverage gaps and enhancing signal penetration through buildings in a cost-effective and low-cost manner.

 

 

Selecting the right semiconductor for 6G communication requires a thorough assessment of key link budget factors, particularly power amplifiers (PA) and low-noise amplifiers (LNA). These components set the upper limits for achievable link performance. In a full transceiver design, additional trade-offs are necessary to balance parameters like linearity, signal combination, power efficiency, spectral efficiency, form factor, and cost.

 

The choice of semiconductor technology hinges on transistor performance, which must be at least three times, and ideally more than five times, the carrier frequency. For effective operation in the sub-THz spectrum (100 GHz – 300 GHz), transistors need to function between 500 GHz and 1 THz. Currently, only SiGe and InP technologies meet these requirements, with a roadmap extending beyond 1 THz.

 

For frequencies up to 150 GHz, CMOS technology is sufficient for short-range communication devices. However, for longer-range applications, higher-performing semiconductors like SiGe or III-V materials may be required, especially for power amplification. As frequencies exceed 200 GHz, a hybrid approach becomes necessary, combining CMOS for logic functions with III-V transistors for low-noise and power amplification.

 

In the 200 GHz to 500 GHz range, SiGe BiCMOS technology strikes an optimal balance between performance, cost, and integration ease. For applications demanding the highest performance, especially in the terahertz range, InP technology stands out, though it may come with higher costs. Figure 1 summarizes the key semiconductor technologies suited for operation above 100 GHz, highlighting their applicability based on the specific frequency range and performance needs.

 

 

 

Antenna-in-package (AiP) technology is key for high-frequency telecommunications, particularly in the mmWave and sub-THz ranges. By leveraging the short wavelengths of these frequencies, AiP allows for the integration of smaller antennas directly into semiconductor packages, unlike traditional antennas mounted separately on PCBs. This integration enhances antenna performance and significantly reduces the overall package size.

 

As 6G technology approaches, research is focused on advancing AiP to integrate antennas directly onto RF components. However, this remains in the research phase due to manufacturing and scalability challenges.

 

 

In the development of AiP technology for high-frequency communication devices, cost-effectiveness is paramount, aiming for a target price of $2 per 1×1 AiP module to enable widespread adoption. Achieving affordability involves overcoming a chicken-and-egg challenge where adoption must precede cost reduction through economies of scale. Utilizing cost-effective packaging materials and processes and ensuring miniaturization is crucial, especially for integration into consumer devices like smartphones. High performance is vital, necessitating the fabrication and integration of high-gain, broadband mmWave antenna arrays, alongside addressing electromagnetic compatibility (EMC) and optimizing signal integrity (SI) and power integrity (PI). Reliability is ensured through efficient heat dissipation, while scalability enables modules to meet diverse application needs. IDTechEx’s report “Antenna in Package (AiP) for 5G and 6G 2024-2034: Technologies, Trends, Markets” delves into key considerations such as antenna element choice, substrate technology, integration of passive devices, and supply chain maturity.

 

When selecting the appropriate substrate technology for AiP, several critical factors must be considered, including core material properties like thermal expansion, Young’s modulus, moisture absorption, and thermal conductivity. The substrate’s manufacturing capabilities—such as via size, metal layer counts, and line/space features—also play a significant role. Antenna performance depends on low dielectric constant (Dk) for wider bandwidth and higher gain, low dielectric loss (Df) for better efficiency, and materials with high Young’s modulus to minimize warpage. Ensuring smooth surface roughness and zero moisture absorption is vital for stable, low-loss interconnects.

 

Currently, four substrate technologies are prominent for AiP: High Density Interconnect (HDI), Low-Temperature Co-fired Ceramics (LTCC), High-Density Fan-Out, and glass. HDI remains the leading choice due to its mature supply chain and cost-effectiveness, despite lagging in advanced routing features compared to emerging technologies like fan-out. Fan-out technology, which supports miniaturization, is expected to gain traction in consumer devices, particularly with the rise of mmWave-enabled wearables.

 

Inorganic substrates like LTCC and glass offer advantages in reliability, with LTCC being widely used in defense and aerospace due to its established supply chain. However, glass substrates, while superior in routing capabilities, face challenges due to their current supply chain immaturity. Despite this, IDTechEx predicts that HDI will continue to dominate AiP applications in 5G and early 6G networks, though the market for LTCC and glass substrates is expected to grow alongside the expanding 5G mmWave market.

 

 

While the precise performance targets needed for 6G are still unknown, it can be expected that next-generation low-loss materials must, at a minimum, surpass the performance of current ultra-low-loss materials. As such, some researchers are approaching the challenge of 6G low-loss materials from the starting point of current commercially used low-loss materials. These material approaches may incorporate novel structures or modifiers into industry-standard dielectric materials, such as PTFE (polytetrafluoroethylene) and reinforced epoxy thermosets.

 

Others are considering the need for low-loss materials for integrated packages. As telecommunications components continue to be integrated into smaller packages, the need for materials that facilitate such packages increases. Organic materials such as polyimide (PI) and poly p-(phenyl ether) (PPE) are being developed into build-up materials for substrates.

 

However, more substantial research activity is taking place for inorganic materials for integrated packages. Numerous papers have been published demonstrating the feasibility of using glass as a substrate in an antenna-integrated die-embedded package, which may reduce signal loss in the interconnects. Additionally, many papers are exploring novel ceramic compositions for low-temperature co-fired ceramics (LTCC) for 6G applications.

 

Lastly, other research approaches utilize less conventional materials, like low-cost thermoplastics, silica foams, or wood-based composites. The diversity in approaches explored by IDTechEx shows not only the level of interest in low-loss materials for 6G but also offers a look into how diverse the future landscape of low-loss materials for 6G may be.

 

 

 

The development of 6G technology has rapidly progressed since 2017. China and the US initiated 6G research early on, highlighting global interest in next-generation wireless technology. Collaborative efforts like the US Next G Alliance, Japan’s B5G consortium, and the EU’s Hexa-X project have fostered international innovation.

 

Significant advancements include China launching its first 6G satellite and companies like Apple integrating satellite-based services in their devices. According to IDTechEx, 6G technology will gradually emerge around 2028, with commercialization expected by 2030. The 3GPP standardization process, beginning in 2026, will be crucial for its adoption.

 

Source: idtechex.com