What is Backside Power Delivery (BSP)? Redefining the Chip Power Map for the 2nm Revolution

Did you grasp this "flip side" revolution in chip design? What else are you curious about regarding Backside Power Delivery, or where do you think it will make the biggest impact first?

The "Flip Side" Revolution in Chip Design: Why Backside Power Delivery (BSP) is the Path Forward Beyond 2nm

Imagine rush hour in a major city downtown. Subways, buses, cars, and scooters are all crammed onto the same main street – it's enough to make you question existence, right? Chip design used to be a bit like that. The "signal wires" carrying data and the "power lines" supplying electricity were all squeezed into the tiny space on the chip's frontside, constantly jostling for position. As chips get smaller and circuits become denser, moving towards 2nm and beyond, not only does signal traffic jam up (higher latency), but power delivery also takes detours, wasting energy and potentially causing "voltage droops" (unstable voltage), limiting performance improvements.

Then, a group of brilliant engineers had a lightbulb moment: "If surface traffic is so congested, why don't we move all the power lines and cables underground?" And thus, Backside Power Delivery (BSP) technology, sometimes called Backside Power Delivery Network (BSPDN), was born. This isn't some shady backdoor shortcut; it's a brand-new highway built by the main forces, delivering power directly from the "backside" of the chip, leaving the precious frontside real estate entirely for the crucial signal lines. This "flip side" revolution initiated by BSP is quietly rewriting the rules of the game for future high-performance chips.

Frontside Gridlock! What Bottlenecks Did Traditional Power Delivery Face?

Before diving into the wonders of BSP, let's first look at the troubles faced by traditional Frontside Power Delivery.

In conventional designs, a chip is like a skyscraper, with each floor (metal interconnect layer) having intricate wiring (interconnects). Some wires carry data signals (like network cables), while others supply power (like power lines). As chip manufacturing processes shrink down to 5nm, 3nm, and head towards 2nm, the space within this skyscraper gets increasingly cramped, yet more and more sophisticated wiring needs to be packed in.

This leads to several serious problems:

1. Routing Congestion:  Power and signal lines fight for the limited space on the frontside metal layers, interfering with each other and making routing increasingly difficult and complex. Imagine trying to thread a new fiber optic cable through a wall already packed with water pipes and electrical wires – the difficulty is immense.
   

2. Increased IR Drop:  Current has to travel through longer and thinner metal lines to reach all corners of the chip. Just like water pressure drops when flowing through long, narrow pipes, the voltage drops along these paths. This IR drop (Voltage = Current × Resistance) can cause chip instability and performance degradation, especially under heavy load.
   

3. Power Consumption & Thermal Issues:  The convoluted power delivery paths increase electrical resistance, causing more energy to dissipate as heat (P=I2R). This increases the chip's power consumption and temperature, hindering the pursuit of ultimate performance and energy efficiency.
   

4. Limited Logic Density:  To ensure stable power supply, power lines often need to occupy significant routing area. This limits the possibility of placing more logic cells on the chip's frontside, hindering further increases in chip density.

It's precisely these escalating challenges that forced the semiconductor industry to seek new solutions, and BSP technology, which moves the power network to the chip's backside, emerged as the center of attention.

Flipping Over for Open Space: How Does BSP Technology Work?

The core concept of Backside Power Delivery is quite intuitive: move the power delivery network from the chip's frontside (which has multiple metal interconnect layers for signals) to the backside (the other side of the silicon substrate). It's like completely separating a city's power grid from its traffic signal system – one runs underground, the other on the surface, without interfering with each other.

Achieving this requires the coordination of several key technologies:

1. Wafer Thinning:  First, the backside of the silicon wafer carrying the transistors must be ground down, making it extremely thin. Typically, the thickness needs to be reduced from the original ~700-800 micrometers (µm) down to just 20-30 µm or even less. It's like grinding a thick book down to just a few pages to allow processing on the back. This process demands extremely high precision control to prevent wafer breakage or warping. Temporary Bonding techniques are often used, where the thinned wafer is temporarily attached to a carrier wafer for subsequent processing steps.
   

2. nano-Through Silicon Via (nTSV):  Next, tiny vertical channels are etched on the thinned wafer's backside and filled with metal (like Tungsten, W, or Copper, Cu) to form nano-Through Silicon Vias (nTSVs). These nTSVs act like "vertical elevators" connecting the underground power system to the surface users, directly delivering power from the backside to the frontside transistors. The diameter of nTSVs is incredibly small, ranging from about 50 to 150 nanometers (nm), and they must be precisely aligned with the transistor contacts on the frontside, making the technology quite challenging.
   

   

   Diagram illustrating Backside Power Delivery (BSP) technology: Through nano-Through Silicon Vias (nTSVs), the power delivery network located on the chip's backside (labeled "Power") is directly connected to the frontside signal layers ("Signal Layers"). This achieves separation of power and signal paths, addressing routing congestion and performance bottlenecks associated with traditional frontside power delivery.

   
   

3. Backside Metallization:  Specialized metal wiring layers are fabricated on the wafer backside to create a complete power delivery network. These wires are generally wider and thicker than the frontside signal lines to reduce resistance and ensure stable, efficient power transmission.
   

4. Integration with Frontside Signal Layers: Finally, the backside power network is connected to the frontside logic cells via the nTSVs, while ensuring good isolation between power and signals to prevent interference.

Through this design, BSP successfully "separates" the power and signal systems, offering a promising solution to the bottlenecks of frontside power delivery.

Why is BSP the "Bee's Knees"? Three Key Advantages Explained

Flipping the power network to the backside isn't just cool; it brings several tangible benefits:

1. Significant IR Drop Reduction: This is one of BSP's most direct and crucial advantages. Since power no longer needs to navigate the complex multi-layered metal routes on the frontside but takes a "shortcut" directly from the back via nTSVs, the delivery path is much shorter, and resistance is significantly lowered. This effectively controls the IR Drop. According to data released by Intel for its PowerVia technology (Intel's version of BSP), PowerVia can reduce IR Drop by about 30% compared to traditional frontside power delivery. Lower IR Drop means more stable voltage supply, allowing the chip to operate reliably at higher clock speeds and reducing logic errors caused by voltage instability, thus enhancing overall performance and reliability.
   

2. Increased Chip Density & Design Flexibility: With the bulky power lines moved from the front, the frontside metal interconnect layers have more room dedicated solely to signal routing. This allows engineers to design more compact and efficient Standard Cells – the basic logic gates that form processors, memory, etc. Traditionally, standard cell height is measured in "Tracks" (number of metal routing tracks), with 6T (6-Track Height) being common. However, with BSP freeing up routing space, designers can potentially shrink standard cells down to 5T or even lower. Smaller standard cells mean more logic units can be packed into the same chip area, significantly increasing the chip's logic density (studies and simulations by imec suggest density improvements of 10-20% or more), or reducing the chip size for the same logic count, lowering costs. Collaborative research between Arm and imec has validated this, showing that 5T designs using BSP can maintain power levels while improving logic coverage.
   

3. Improved Power Efficiency & Thermal Management: Shorter power delivery paths not only reduce IR drop but also minimize energy loss during transmission (P=I2R; lower resistance R leads to lower power loss P), enhancing the chip's Power Efficiency. Furthermore, moving the main power network to the back helps with heat dissipation. One major heat source (power line resistance) is relocated away from the primary logic operation heat zone (transistors). The backside metal layers are often thicker and better at dissipating heat, helping to spread out Hotspots and lower the chip's peak temperature. According to thermal simulations by imec and early data from Intel's PowerVia, BSP architectures have the potential to reduce chip hotspot temperatures by several degrees Celsius (e.g., 5°C or more). This is crucial for AI or HPC chips requiring sustained high-load operation, as it helps maintain stability at high frequencies and mitigates aging effects like electromigration.

Overall, BSP technology addresses challenges in performance, density, power, and thermals through structural innovation, which is why it's considered a key enabler for continuing Moore's Law towards 2nm and beyond.

Clash of the Titans: Comparing BSP Technologies from TSMC, Intel, & Samsung

In the crucial battleground of BSP, the world's top three foundry giants – TSMC, Intel, and Samsung – are naturally all in, presenting their own solutions and planning their implementation in future advanced process nodes.

Here's a summary of each company's BSP technology plans as known around late 2024 / early 2025:

Company	BSP Technology Name	Target First Node	Announced/Expected Ramp	Key Technology Highlights	Claimed Benefits/Goals
Intel	PowerVia	Intel 20A	Ramping end of 2024	Industry's first mass-produced monolithic BSP architecture, paired with RibbonFET (GAA) transistors.	6% frequency uplift; ~30% IR drop reduction; cell density improvement. Optimization continues for Intel 18A (2025).
TSMC	Super PowerRail	A16 (1.6nm-class)	Expected H2 2026	Combines Nanosheet (GAA) transistors, BSP, and advanced packaging (e.g., CoWoS) for system-level optimization.	Vs. N2P: 8-10% speed boost, 15-20% power reduction, up to 10% logic density increase.
Samsung	BSPDN (Tentative)	SF2Z (2nm-class)	Expected 2027	Integrating BSPDN into their second-gen 2nm process (SF2), paired with their GAA transistor tech (MBCFET).	Vs. SF2: Expected further improvements in performance, power, and area (specifics TBD).

(Note: Timelines and figures are based on public announcements and targets; actual production schedules and performance may vary based on technological progress and market conditions.)

From the table, we can see:

• Intel took the lead in BSP mass production timing. Its PowerVia technology debuted with the Intel 20A process and will be refined for the subsequent 18A node, showcasing its determination to regain process technology leadership.
  

• TSMC positions its BSP technology (Super PowerRail) as a key feature of its A16 node (the generation following N2/N2P). Combined with its mature Nanosheet transistors and advanced packaging, it aims to deliver comprehensive system-level performance gains in 2026.
  

• Samsung also plans to introduce BSPDN in its SF2Z process. Although slightly later, it's considered a vital weapon for enhancing competitiveness in the latter half of the 2nm generation.

Interestingly, the development of BSP technology often goes hand-in-hand with the next-generation transistor architecture, GAA (Gate-All-Around) – such as Intel's RibbonFET, TSMC's Nanosheet, or Samsung's MBCFET. Combining these two maximizes the advantages of advanced process nodes in performance, power, and density (PPAD). It's foreseeable that BSP + GAA will become the two main pillars driving semiconductor technology forward in the post-Moore era.

Where BSP Shines: Which Applications Need It Most?

While BSP offers numerous benefits, its initial implementation cost is high and the process is complex. Therefore, the first adopters will be high-value applications demanding the utmost in performance, power efficiency, and density:

1. High-Performance Computing (HPC) & Data Center Processors (Server CPU/GPU): Whether it's supercomputers running scientific simulations and climate predictions or data centers powering cloud services and big data analytics, processors need to operate stably for long durations under extremely high power loads (often hundreds of watts). BSP's low IR drop, high power efficiency, and improved thermal management perfectly meet the stringent requirements of HPC and server chips for extreme performance and stability. Intel's Xeon CPU series and data center GPUs (like Gaudi) are expected early beneficiaries of PowerVia.
   

2. Artificial Intelligence (AI) Accelerators (GPU/TPU/NPU): Training large AI models (like the GPT series) or performing complex AI inference requires massive computational power. Current AI chips (like Nvidia's H100/B100, Google's TPUs) are already power behemoths, and future models will only get larger and more complex. BSP enables higher chip density (packing more compute units), higher clock speeds, and effective power/thermal management, making it crucial for building the next generation of more powerful and energy-efficient AI accelerators. TSMC's A16 process with Super PowerRail clearly targets this rapidly growing market.
   

3. High-End Mobile SoCs (System on Chips): Although power constraints are much tighter in mobile devices than servers, the demand for performance and integration keeps rising (e.g., stronger CPUs/GPUs, faster AI processing, complex image processing). BSP's freed-up frontside routing space and improved power efficiency help pack more powerful features within limited volume and battery life while maintaining good thermal performance. Future generations of Apple's A-series or M-series chips, Qualcomm's Snapdragon flagships, etc., are likely candidates for adopting BSP technology beyond the 2nm node.
   

4. Advanced Communication Chips (e.g., 5G/6G Baseband): 5G and future 6G base stations and terminal devices need to handle extremely high bandwidth, low-latency signals while integrating complex digital signal processing and control logic. BSP helps to better isolate sensitive radio frequency (RF) circuits from digital logic circuits within highly integrated SoCs, reducing noise interference and improving overall system performance and stability.

Essentially, any field relentlessly pursuing Performance per Area and Performance per Watt is likely to see BSP technology in the future.

The Road Ahead: Challenges and Future Outlook for BSP

Despite its promising prospects, realizing and popularizing BSP still faces considerable technical and manufacturing challenges:

• Extreme Wafer Thinning & Handling:  Grinding wafers down to below 20 µm while maintaining flatness, uniformity, and preventing breakage or warping during subsequent processes is a major hurdle. This requires advanced grinding, polishing, bonding, and debonding technologies.
  

• High Aspect Ratio nTSV Fabrication:  Creating nTSVs with diameters of tens of nanometers but depths of several or even tens of micrometers, including etching, metal filling, and precise alignment (Overlay Accuracy) with frontside transistors, demands extremely tight process control, directly impacting yield and reliability.
  

• Thermal Budget Control for Backside Process:  Processes performed on the wafer backside (like metallization) must not exceed certain temperatures to avoid damaging the delicate transistor structures already built on the frontside.
  

• Increased Design & Verification Complexity:  EDA (Electronic Design Automation) tools need upgrades to support layout, routing, simulation, and verification for BSP architectures, making the design flow more complex.
  

• Packaging & Testing Integration:  With chips becoming "double-sided," new packaging techniques (like integrating Flip-Chip + BSP) and testing methodologies are needed to ensure final product quality.
  

• Cost Factor:  The additional backside processing steps inevitably increase manufacturing costs. Initially, only the highest-end chips might be able to afford it.

Future Outlook:

Despite the challenges, BSP is widely regarded as an indispensable technology for continuing semiconductor scaling trends. With Intel's PowerVia leading the charge into mass production, and TSMC and Samsung actively following suit, we can expect:

1. Gradual Proliferation:  BSP technology will start with the most advanced nodes like 20A/A16/SF2Z and gradually expand to more diverse applications as the technology matures and costs decrease.
   

2. Continuous Optimization:  Future BSP technologies might involve more complex backside metal layer structures, more precise nTSV processes, and even tighter integration with heterogeneous integration techniques like 3D stacking.
   

3. Ecosystem Maturation:  EDA tool vendors, equipment manufacturers, and material suppliers will continue to roll out solutions supporting BSP, forming a complete industry ecosystem.

In conclusion, BSP is more than just a process technology innovation; it represents a "paradigm shift" in chip design thinking. By separating power and signal delivery, it opens up new possibilities for overcoming the physical limits facing semiconductor development in the coming decades. This ongoing "flip side revolution" is definitely worth keeping a close eye on.