Advanced Packaging Methods for Semiconductors

Packaging bottlenecks for chiplets, heterogeneous integration, 2.5D/3D packaging, interposer and substrate design. Core packaging bottlenecks Die-to-die interconnect: Bandwidth density, latency, power per bit, equalization at fine pitches; UCIe vs AIB/BoW interoperability and PHY maturity. Power delivery and IR drop: PDN co-design across dies/interposer/substrate; decap placement limits; simultaneous switching noise. Thermals and warpage: Hotspots from asymmetric workloads; buried-die heat removal; CTE mismatch across silicon/organic/glass; assembly-induced stress. Yield multiplication: KGD insufficiency; “known good system” remains hard; redundancy/spare lanes and repair needed. Capacity and cost: Advanced packaging tool/OSAT constraints 2.5D packaging (interposers/bridges) Silicon interposers (CoWoS/SoIC/EMIB): Fine-pitch RDL for HBM and chiplets but high cost, TSV-induced stress, interposer yield, and reticle stitching complexity. Bridges (EMIB/Si-bridge): Localized high-density links reduce full interposer cost but add routing/placement constraints and SI/PI discontinuities. Glass interposers: Lower loss and better CTE vs organic; immature supply chain, via/RDL processes, and reliability data. Active vs passive interposers: Active aids retiming/voltage regulation but adds heat, complexity, and new failure domains. 3D stacking Vertical interconnect: Micro-bumps vs hybrid bonding (Cu–Cu) trade-offs in pitch, parasitics, yield; TSV keep-out zones hurt area. Thermal limits: Stacked logic/HBM create heat removal barriers; need heat vias, thermal TSVs, microfluidics, or die thinning. Power integrity: Tier-to-tier IR drop and resonances; backside power delivery helps but complicates thermal path and process flow. Assembly/yield: Wafer-to-wafer vs die-to-wafer choices; binning alignment; rework ability is low. Interposer and substrate design Signal integrity: Loss/crosstalk at multi-GHz; channel uniformity, impedance control, return paths; accurate S-parameter extraction. PDN architecture: multi-domain power islands, via farms, ground meshes; placement of on-interposer decaps and IVRs. Routing density: Fine L/S on interposer RDL vs limits of organic substrates; escape routing for HBM channels and wide UCIe links. Material choices: Organic (HDI) for cost, silicon for density, glass for low loss/CTE; reliability under temperature/humidity and power cycling. EM isolation: RF/analog coexistence with high-speed digital; guard rings, stitching vias, shielding layers, substrate noise control. Heterogeneous integration pain points Mixed nodes/materials: RF/analog on mature nodes with advanced-node logic; isolation from digital switching noise and supply ripple. Co-packaged optics: Thermal and mechanical co-design; fiber attach tolerances; contamination risk during assembly. Memory proximity: HBM bandwidth vs footprint/thermals; future NVRAM/3D SRAM integration challenges. Please reach out if you are facing any of these challenges

Advanced Packaging is the New Materials battleground. We’ve moved past monolithic chips. Today’s performance gains come from chiplet-based processors mixing CPUs, GPUs, accelerators, and memory in one package. But that leap hinges on materials breakthroughs we still haven’t mastered. → Interposers under fire.  Organic build‑up films (ABF) warp at tight pitches and sap signal integrity. Glass and ceramic‑core interposers promise flatter, lower‑loss alternatives—yet scaling them and matching their CTE to silicon is a steep climb. → Die‑attach dilemma.  Standard solders and epoxies crack under 3D stacking’s thermal/mechanical stress. We need die‑attach materials that cure at low temperature but stand up to 125 °C+ cycles without delaminating. → TIM bottleneck.  Three‑dimensional stacks can push heat flux above 500 W/cm². Liquid‑infused nanocomposite TIMs and graphene‑enhanced interfaces look great in the lab, but integrating them into wafer‑level packaging without voids is a nightmare. → Through‑silicon vias & wafer packaging.  Embedding TSVs demands dielectric liners that don’t fracture under thermal cycling. Ultra‑thin wafers only make the mismatch worse. The engineering community is racing on glass interposers, novel underfills, and nano‑TIMs. But until these materials scale reliably, packaging—not transistors—will throttle tomorrow’s computing power. Are materials scientists ready to fill these gaps? Or will advanced packaging remain the Achilles’ heel of chiplet performance? #AdvancedPackaging  #HeterogeneousIntegration  #ThermalManagement

4 reasons Driving the Shift Toward Advanced Packaging? 1. Moore’s Law Slowdown For decades, the industry relied on shrinking transistors (Moore’s Law) to double performance every 18–24 months. But as we approach sub-3nm nodes, scaling becomes costlier, more complex, and yields drop. It’s no longer economically viable to put everything into one monolithic chip. ➤ Example: Intel and TSMC now integrate multiple smaller chips (chiplets) instead of one giant die. This allows them to continue performance gains without relying solely on node shrinkage. ➤ Analogy: Think of trying to build a mansion on a tiny plot of land — it gets harder and more expensive to squeeze more rooms (transistors) in. Advanced packaging is like building several smaller houses (chiplets) and connecting them with efficient roads (interconnects). 2. Need for Higher Performance and Energy Efficiency Modern applications — especially AI, 5G, AR/VR, and autonomous vehicles — require rapid data transfer between chips, low latency, and reduced power consumption. Advanced packaging allows chips (e.g., logic, memory, I/O) to be placed closer together, reducing signal travel distance, improving speed, and cutting power use. ➤ Example: NVIDIA’s H100 GPU uses HBM3 memory stacked closely using advanced packaging, which massively boosts bandwidth and energy efficiency. ➤ Analogy: It’s like relocating your kitchen, dining, and living areas closer together — less time and effort moving between them means faster and more efficient daily operations. 3. Demand from AI, HPC, and Data Centers AI training models (like ChatGPT), high-performance computing, and hyperscale data centers need massive processing and memory bandwidth — beyond what traditional packaging can deliver. Advanced packaging enables multi-die systems that behave like a single chip but are customized and scalable. ➤ Example: AMD’s EPYC processors use chiplet architecture — separate cores and I/O dies — to scale efficiently while reducing manufacturing cost and complexity. ➤ Analogy: Imagine one person trying to carry everything in a big suitcase (monolithic die). Instead, using multiple backpacks (chiplets) shared across a team (multi-die system) lets you carry more, faster, and more efficiently. 4. Rise of Chiplet-based Architectures to Reduce Cost and Improve Yield Instead of building a large, expensive chip with everything on it (which might fail in testing), companies now split the functions into smaller “chiplets”, manufactured separately and assembled into one package. This improves yield (less waste), flexibility (reuse components), and time-to-market. ➤ Example: Intel’s Meteor Lake uses chiplets built on different process nodes (e.g., TSMC for GPU, Intel for CPU), stitched together using Foveros 3D stacking. ➤ Analogy: It’s like assembling a laptop from modular parts (screen, keyboard, battery) — if one part fails, you can replace or improve just that part, rather than scrapping the entire system.

⚠In the new battleground against “Memory Wall”, #scalability (in terms of maximizing in-package signal bandwidth and reach while minimizing latency and power) is the tip of the spear. 10 months ago, I wrote a post about a 5nm Die-to-Die (#D2D) #PHY:🏷️https://lnkd.in/dUAk5PkP. It was (surprisingly) well received and insightful industry practitioners have sent DMs, one of which pointed me to the “interposer-less” #chiplet #interconnect solution that Eliyan promotes. I was fascinated by not only Eliyan’s innovative concept but its impeccable timing; while the #AI & #HPC market was (and still is) thirsting for specialized, unapologetically pricey silicon interposers! Last April, Eliyan also named Dr. Behzad Razavi, an esteemed expert in Integrated Circuits and Systems at UCLA, its Chief Technologist. (Dr. Razavi’s CMOS IC design books are superb!👍) 10 months later, I'm delighted to see Eliyan’s PR on its 3nm PHY design, the first silicon of which is expected to materialize in Q3 2024: 📝Although the design will utilize standard organic/laminate packaging with [an] 8-2-8 stack up, the highly area efficient NuLink™ PHY is bump limited and leverages innovative interference cancellation techniques to fit under not only 100um bump pitch of standard packaging, but also 55um of #advancedpackaging. 📝HBM suppliers’ willingness to offer custom HBM, in which the bottom die in an HBM stack can have custom circuitry, has provided an easy route for adoption. Eliyan’s [bidirectional] PHY can sit on this die. At its core, Eliyan’s solution is primarily about adding/optimizing integrated PHYs with a goal to do away with interposers. It is a promising solution tailored for enhancing system scalability and design flexibility. In practice, however, a notably larger IC substrate warrants a closer look at engineering risks such as package coplanarity/warpage and area efficiency (perhaps a good reason for employing an 8-2-8 stack up), clock timing/latency mismatch, power delivery hiccup (e.g., IR drop), etc. Assuming the cost of interposers won’t go down fast enough—and that’s a BIG assumption—a handful of industry leaders have touted the so-called “Star-Bus (Tree) Topology” idea. As depicted, the “Stars” (1-4 and so on) are composed of #ASIC (CPU/DPU/GPU/TPU/DLA) dies and peripheral #HBM dies (connected via Cu trace, RDL, EMIB, or even Fiber), and the “Bus” facilitates D2D links by means of either Cu trace, RDL, EMIB, Fiber, or Glass Core Substrate with TGVs. What’s next for scalable chiplet interconnect? Happy to hear your thoughts. Additional reading: 🏷️3nm PHY (Eliyan Corporation): https://lnkd.in/d4UVUmDp 🏷️Article by EE Journal: https://lnkd.in/dc8FGG4R 🏷️Article by EE Times: https://lnkd.in/dJmNZDRR 🏷️4nm HBM3 PHY (Samsung Electronics): https://lnkd.in/dBQjS5JP 🏷️5nm USR PHY (NVIDIA): https://lnkd.in/gghJJZ6q 🏷️7nm USR PHY (MediaTek): https://lnkd.in/gvj9fdma 🏷️7nm LIPINCON (TSMC): https://lnkd.in/gdvJvD75 ➟To be continued. #Chiplets

What’s the difference between 2.5D and 3D ICs? As Moore’s Law slows, the industry is shifting to system-level innovation—especially through advanced packaging. Two approaches lead the charge: 2.5D and 3D ICs. -> 2.5D ICs Chips are placed side-by-side on a common interposer (silicon or glass), which routes connections between them. Think of it as horizontal integration with higher bandwidth and lower latency than traditional PCBs. -> 3D ICs Chips are stacked vertically and connected using TSVs (Through-Silicon Vias)—tiny vertical tunnels through silicon that shorten communication paths between layers. -> Analogy: 2.5D is like a city spread across one giant floor—buildings connected by roads. 3D is a skyscraper—floors stacked with elevators (TSVs) moving data vertically. Faster, denser, but harder to cool and build. 💡 Why it matters: These techniques help us move “beyond Moore” by: Increasing bandwidth Reducing latency Shrinking footprint Combining memory, logic, RF, and more in a single package -> Where it’s used: 2.5D: AMD GPUs, Xilinx FPGAs, HBM-connected AI accelerators 3D: Intel’s Foveros, Samsung HBM stacks, Apple M-series chips, and next-gen edge AI hardware Key takeaway: It’s not just about smaller nodes anymore. Packaging is becoming the new performance lever—and how you connect dies matters as much as what you put on them. P.S. If you're looking for semiconductor news, and insights, check out our Blog The Semiconductor world—a guide to the chip industry in simple terms. Link in comments. #Semiconductors #AdvancedPackaging #2_5D #3DIC #TSV #Foveros #HBM #AIChips #MooresLaw #SystemIntegration #TestFlow #ATOMS #TechoVedas #SemiconSEA