Earlier in June, Samsung updated its roadmap in the Angstrom era, stating that its 2nm node optimized with backside power delivery network (BSPDN), referred to as SF2Z, will enter mass production in 2027. Now, according to the latest report by the Korea Economic Daily, compared with the traditional front-end power delivery technology, BSPDN is said to reduce the size of Samsung’s 2nm chip by 17%.

Citing Lee Sungjae, vice president of the Foundry PDK Development Team at Samsung, on Thursday, the report also notes that by applying BSPDN to its 2nm chips, Samsung is expected to improve the product’s performance and power efficiency by 8% and 15%, respectively.

Lee’s remarks was the first time a Samsung foundry business executive provided details publicly regarding its BSPDN roadmap. The report explains that by positioning the power rails on the back of the wafer to remove bottlenecks between power and signal lines, the production of smaller chips would be easier.

However, Samsung is not the first semiconductor giant to adopt this technology. Among the Big Three in the foundry sector, Intel is at the forefront, aiming to produce chips with BSPDN technology, which it calls PowerVia, with Intel 20A (2 nm) in 2024. The tech giant also plans to implement PowerVia on Intel’s 20A along with the RibbonFET architecture for the full-surround gate transistor.

According to Intel, power lines typically occupy around 20% of the space on the chip surface, while its self-developed PowerVia’s backside power delivery technology saves this space, allowing more flexibility in the interconnect layers.

On the other hand, foundry leader TSMC reportedly plans to integrate its backside power delivery technology, Super PowerRail architecture, and nanosheet transistors in its A16 chip in 2026.

In addition to BSPDN, Samsung also revealed its roadmap about the next-generation gate-all-around (GAA) technology, which the company was first introduced in 2022, according to the report.

Samsung plans to begin mass production of 3 nm chips based on its second-generation GAA technology (SF3) in 2H24 and will also implement GAA in its upcoming 2 nm process, the report notes.

According to Lee, SF3 has enhanced chip performance by 30%, improved power efficiency by 50%, and reduced chip size by 35% compared to the chips produced with the first-generation GAA process. Coupling with the adoption of BSPDN, the two technologies can further reduce the chip size for Samsung.

Read more

• [News] Samsung Unveils Next-gen 2nm Node Roadmap; SF2Z with Backside Power Delivery to Enter Production in 2027
• [News] TSMC’s Backside Power Delivery Reportedly Set for 2026, Benefiting the Supply Chain

(Photo credit: Samsung)

As semiconductor manufacturing processes evolve more gradually, 3D packaging emerges as an effective means of prolonging Moore’s Law and enhancing the computational prowess of ICs. Within the realm of 3D stacking technology, the Interuniversity Microelectronics Centre (imec) based in Belgium categorizes 3D integration technologies into four distinct types, each determined by different partitioning locations within a chip: 3D-SIP, 3D-SIC, 3D-SOC, and 3D-IC. Based on our previous discussion of 3D-SIP and 3D-SIC stacking, this article places a spotlight on the other two technologies: 3D-SOC and 3D-IC.

Related Article: Differences Between 3D-SIP and 3D-SIC: Why Are TSMC, Intel, and Samsung All Actively Involved?

3D-SOC

A System on Chip (SOC) involves the redesign of several different chips, all fabricated using the same manufacturing process, and integrates them onto a single chip. 3D-SOC takes this concept to new heights by stacking multiple SOC chips vertically. The image below illustrates the transformation of a 2D System on Chip (2D-SOC), where circuits are redivided into blocks, and then stacked to form a 3D System on Chip (3D-SOC).

Source: imec

imec’s research team previously published a paper on IEEE, outlining the advantages of 3D-SOC and backside interconnects. This technology aims to achieve the integration of diverse chips in a heterogeneous system. By intelligently partitioning circuits, it significantly reduces power consumption and boosts computational performance. In comparison to the trending chiplet technology, 3D-SOC holds a competitive edge.

Eric Beyne, IMEC’s Vice President of Research and Project Director for 3D System Integration, pointed out, “Chiplets involve separately designed and processed chiplet dies. A well-known example are high-bandwidth memories (HBMs) – stacks of dynamic random access memory (DRAM) chips. This memory stack connects to a processor chip through interface buses, which limit their use to latency-tolerant applications. As such, the chiplet concept will never allow for fast access between logic and first and intermediate level cache memories.”

However, it’s essential to acknowledge that 3D-SOC technology comes with apparent drawbacks, primarily higher research and development costs and a longer development timeline compared to 3D-SIP technology. Nevertheless, as applications like AIGC, AR/VR, 8K, and others continue to drive the need for high-speed computing, chips are relentlessly progressing towards higher efficiency, lower power consumption, and smaller size. In this context, 3D-SOC technology will maintain its place in advanced packaging.

Backside Power Delivery Network (BSPDN)

The technology of Backside Power Delivery Network (BSPDN) represents a pivotal development in semiconductor manufacturing, offering several advantages, including more flexible circuit design, shorter metal wire lengths, and higher chip utilization. After transforming a 2D System on Chip (2D-SOC) into a 3D-SOC through layered stacking, the original back sides of the chips become the outer sides of the 3D-SOC. At this stage, the “freed-up” backside of the chips can be utilized for signal routing or as power lines for transistors, in contrast to traditional processes where wiring and power lines are designed on the front side of the wafer.

In the past, backside chips were merely used as carriers, but BSPDN technology allows for more space to be used for logic wafer design. According to simulation results, the transmission efficiency of backside PDN is seven times higher than traditional front-side PDN. Intel has also announced the introduction of this technology in the 20Å and 18Å processes.

To achieve BSPDN, a dedicated wafer thinning process (reducing it to a few hundred nanometers) is required, along with nanoscale through-silicon vias (nTSV) to connect backside power to the front-side logic chip.

Another key technology for BSPDN is the Buried Power Rail (BPR), a miniaturization technique that embeds wires beneath the transistors, with some inside the silicon substrate and others in shallow trench isolation oxide layers. BPR replaces power lines and ground lines under standard cells in traditional processes and further reduces the width of standard cells, mitigating IR voltage drop issues.

The diagram below illustrates BSPDN, where backside PDN’s metal wiring is connected to Buried Power Rails (BPR), and the backside of the chip (BS) is connected to the front side of the logic chip (FS).

Source: imec

3D-IC

The final category, 3D-IC, employs new 3D sequential technology (S3D) or Monolithic technology to vertically stack n-type and p-type transistors, forming a Complementary Field-Effect Transistor (CFET). This technology enables two transistors to be stacked and integrated into the size of a single transistor. This not only significantly increases transistor density but also simplifies the layout of CMOS logic circuits, enhancing design efficiency. As seen in the diagram below, n-type and p-type transistors are integrated vertically to form a CFET.

Source: imec

Nevertheless, the key challenge lies in how to vertically integrate each minuscule transistor and address heat dissipation issues under high-speed computing. Major manufacturers are still in the development phase, but the technology’s biggest advantage lies in achieving the highest component density and the smallest node width, even without nodes. With the continuous increase in demand for high-speed computing, 3D-IC technology is set to become a focal point in the industry’s development.

3D Stacking Leading the Global Semiconductor Advancement

imec has outlined a roadmap for 3D stacking, aiming to reduce pitch spacings and increase point density within unit areas. However, imec also emphasizes that the development of 3D packaging technologies does not follow a linear timeline, as depicted in the figure above, as there is no single packaging technology that can cater to all requirements.

With the rapid development of applications such as AIGC, AR/VR, 8K, 5G, and others, a significant demand for computing power is expected to persist. To overcome the bottlenecks in semiconductor process technology, countries worldwide are fully engaged in advanced packaging research, and 3D stacking undoubtedly takes the center stage as the elixir for Moore’s Law continuation.

Explore More

• An In-Depth Explanation of Advanced Packaging Technology: CoWoS
• Intel and Samsung Join TSMC in Fierce Advanced Packaging Race
• Continuing Moore’s Law: Advanced Packaging Enters the 3D Stacked CPU/GPU Era
• Understanding Chiplets, SoC, and SiP: Why TSMC, Intel, Samsung Invest?

(Image: Samsung)

As per a report from Taiwan’s TechNews,” TSMC, Samsung, and Intel have been actively deploying Backside Power Delivery Network (BSPDN) strategies recently, and have announced plans to incorporate BSPDN into their logic chip development roadmap. For instance, Samsung intends to implement BSPDN technology in its 2-nanometer chips, a move unveiled at the VLSI Symposium in Japan.

According to imec, BSPDN aims to alleviate the congestion issues faced by front-end logic chips in later-stage processes. Through Design Technology Co-Optimization (DTCO), more efficient wire designs are achieved in standard cells, aiding in the downsizing of logic standard cell.

In essence, BSPDN can be seen as a refinement of chiplet design. The conventional approach, where logic circuits and memory modules are integrated, is transformed into a configuration with logic functions on the front and power or signal delivery from the back.

While the traditional method of front-side wafer power delivery achieves its purpose, it leads to decreased power density and compromised performance. Nevertheless, the new BSPDN technique has not yet been adopted by foundries.

Samsung claims that, compared to the conventional method, BSPDN reduces area by 14.8%, providing more chip space for additional transistors and improved overall performance. Wire lengths are also cut by 9.2%, reducing resistance, allowing greater current flow, and thereby lowering power consumption while enhancing power transmission efficiency.

In June of this year, Intel also introduced its BSPDN-related innovations under the name ‘PowerVia.’ Team Blue plans to utilize this approach in the Intel 20A process, potentially achieving a chip utilization rate of 90%.

Intel believes PowerVia will address interconnect bottlenecks in silicon architecture, enabling continuous transmission through backside wafer powering. The company anticipates incorporating this novel approach into its Arrow Lake CPUs slated for release in 2024.

Furthermore, according to Taiwan’s supply chain sources, TSMC remains on track to launch its 2-nanometer process in 2025, with mass production expected in the latter half of the year in Hsinchu’s Baoshan. The company’s N2P process, planned for 2026, will feature BSPDN technology.

(Photo credit: Samsung)