As semiconductor fabrication technologies continue to advance, the number of transistors in integrated circuits (ICs) has steadily increased. Initially, ICs contained only tens of transistors, but as technology progressed, ICs integrating hundreds of thousands of transistors enabled the realization of 3D animation. ICs with millions of transistors allowed computers to enter households, and today, ICs with hundreds of billions or even trillions of transistors enable digital technology to connect the entire world, profoundly impacting people’s lives.

Over the past 65 years, semiconductor fabrication processes have rapidly evolved, driven by Moore’s Law, gradually reshaping society. However, in recent years, semiconductor processes have approached physical limits, and the failure of Moore’s Law has been a topic of concern. In response, 3D IC stacking and heterogeneous integration technologies have emerged as promising solutions.

3D Stacking Trends

With the rapid development of applications such as AI, AR/VR, and 8K, a significant demand for computation is expected to continue, particularly driving parallel computing systems capable of handling vast amounts of data in a short time. As semiconductor processes slow down, 3D packaging has become an effective means to extend Moore’s Law and enhance IC computing performance.

3D packaging technology offers numerous advantages over traditional 2D packaging. It enables size reduction, with silicon interposer efficiency exceeding 100%, improved connectivity, reduced parasitic effects, lower power consumption, lower latency, and higher operating frequencies. These advantages, along with various benefits of 3D integration and interconnection technologies, make 3D packaging a development direction pursued by major players in the industry.

imec’s Vision for 3D Technology

In the field of 3D stacking technology, imec (imec, the Belgian Interuniversity Microelectronics Centre) defines four categories of 3D integration solutions: 3D-SIP, 3D-SIC, 3D-SOC, and 3D-IC, each requiring different process solutions and 3D integration techniques. Eric Beyne, VP R&D, Director 3D System Integration Program at imec specifically notes that concerning 3D interconnection technology, the scope of 3D interconnection will extend from stack packaging below 1 millimeter (mm), such as Package-on-Package (POP), to below 100 nanometers (nm) with true 3D ICs using transistor stacking, surpassing an interconnect density of 108/mm².

imec identifies three key elements in 3D integration technology: Through-Silicon Via (TSV), die-to-die and die-to-wafer stacking and interconnection, and wafer-to-wafer bonding technology. Beyne points out that TSV miniaturization technology continues to evolve. However, regarding “interconnect gaps,” as TSVs further shrink, microbump technology may struggle to meet higher interconnection demands, making cu-cu hybrid bonding technology a focus of development.

▲The image shows imec’s 3D interconnect technology roadmap, illustrating that as packaging technology continues to advance, node sizes shrink, and density further increases in 3D packaging. (Source：ISSCC 2021)

3D-SIP

System-in-Package (SIP), a form of system-level packaging, connects multiple chips that undergo different fabrication processes and preliminary packaging using heterogeneous integration techniques, integrating them within the same packaging shell. 3D-SIP involves vertically stacking multiple SIP chips, including packaging interconnects, fan-out wafer-level packaging, and solder ball bonding.

▲The image on the left is a schematic diagram of 3D-SIP packaging, where the connection points on both sides of the PCB board link the chips that have undergone initial packaging from top to bottom. The image on the right is an actual product illustration. (Source：TrendTorce (Left)，ISSCC 2021(Right))

Currently, the connection pitch in existing solutions is approximately 400 micrometers (µm). imec’s research aims to increase the interconnectivity of such SIPs by 100 times, reducing connection pitch to 40 µm. Common applications of 3D-SIP packaging include RF FEMs, TWS Barbuds SoCs.

3D-SIC

The second category, 3D-SIC (Stacking IC), involves the stacking of individual chips on top of each other. 3D-SIC is achieved by stacking chips on an interposer or wafer, with the finished chips bonded to the top of the wafer. Chips are interconnected through TSVs and microbumps, with industry solutions achieving pitch sizes as small as 40 µm. The technology is applied to products like 3D-DRAM and logic chips, connected alongside optical I/O units on the interposer. Currently, 3D-SIC technology is widely used in High-Bandwidth Memory (HBM) manufacturing.

▲The image depicts a schematic diagram of 3D-SIC, which utilizes cu-cu hybrid bonding technology to connect the upper and lower layers of ICs. (Source:imec)

3D stacking packaging is leading the global semiconductor industry, and imec has outlined a development blueprint focused on reducing interconnection pitch and increasing contact density per unit area, positioning 3D stacking as a solution to continue Moore’s Law amid slowing semiconductor processes.

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?

This article is from TechNews, a collaborative media partner of TrendForce.

(Photo credit: TSMC )

Semiconductor process technology is nearing the boundaries of known physics. In order to continually enhance processor performance, the integration of small chips (chiplets) and heterogeneous Integration has become a prevailing trend. It is also regarded as a primary solution for extending Moore’s Law. Major industry players such as TSMC, Intel, Samsung, and others are vigorously developing these related technologies.

What are SoC, SiP, and Chiplet?

To understand Chiplet technology, we must first clarify two commonly used terms: SoC and SiP. SoC (System on Chip) involves redesigning multiple different chips to utilize the same manufacturing process and integrating them onto a single chip. On the other hand, SiP (System in Package) connects multiple chips with different manufacturing processes using heterogeneous integration techniques and integrates them within a single packaging form.

Chiplet technology employs advanced packaging techniques to create a SiP composed of multiple small chips. It integrates small chips with different functions onto a single substrate through advanced packaging techniques. While Chiplets and SiPs may seem similar, Chiplets are essentially chips themselves, whereas SiP refers to the packaging form. They have differences in functionality and purpose.

Chiplets: Today’s Semiconductor Development Trend

The design concept of Chiplet technology offers several advantages over SoC, notably in significantly improving chip manufacturing yield. As chip sizes increase to enhance performance, chip yield decreases due to the larger surface area. Chiplet technology can integrate various smaller chips with relatively high manufacturing yields, thus enhancing chip performance and yield.

Furthermore, Chiplet technology contributes to reduced design complexity and costs. Through heterogeneous integration, Chiplets can combine various types of small chips, reducing integration challenges in the initial design phase and facilitating design and testing. Additionally, since different Chiplets can be independently optimized, the final integrated product often achieves better overall performance.

Chiplets have the potential to lower wafer manufacturing costs. Apart from CPUs and GPUs, other units within chips can perform well without relying on advanced processes. Chiplets enable different functional small chips to use the most suitable manufacturing process, contributing to cost reduction.

With the evolution of semiconductor processes, chip design has become more challenging and complex, leading to rising design costs. In this context, Chiplet technology, which simplifies design and manufacturing processes, effectively enhances chip performance, and extends Moore’s Law, holds significant promise.

Applications and Development of Chiplets

In recent years, global semiconductor giants like AMD, TSMC, Intel, NVIDIA, and others have recognized the market potential in this field, intensively investing in Chiplet technology. For example, AMD’s recent products have benefited from the ‘SiP + Chiplet’ manufacturing approach. Moreover, Apple’s M1 Ultra chip achieved high performance through a customed UltraFusion packaging architecture. In academia, institutions like the University of California, Georgia Tech, and European research organizations have begun researching interconnect interfaces, packaging, and applications related to Chiplet technology.

In conclusion, due to Chiplet technology’s ability to lower design costs, reduce development time, enhance design flexibility and yield, while expanding chip functionality, it is an indispensable solution in the ongoing development of high-performance chips.

This article is from TechNews, a collaborative media partner of TrendForce.