As semiconductor packaging technologies evolve, advanced methods like 2.5D and 3D Cu-to-Cu hybrid bonding are essential for achieving higher performance and power efficiency.
By Dr Yu-Han Chang, principal technology analyst at IDTechEx
However, manufacturing these technologies to meet high performance and yield standards while fulfilling client requirements is complex. Challenges include developing the right materials and innovating packaging manufacturing techniques.
IDTechEx’s “Materials and Processing for Advanced Semiconductor Packaging 2025-2035: Technologies, Players, Forecasts” report offers in-depth insights into these challenges. Drawing on IDTechEx’s expertise, the report explores key trends in 2.5D packaging materials and process flow, as well as the innovative Cu-to-Cu hybrid bonding technology for 3D packaging.
Additionally, it provides a 10-year market forecast for Organic Dielectric Advanced Semiconductor Packaging Modules, covering unit and area projections, offering valuable foresight for industry stakeholders.
2.5D interposer materials
In 2.5D packaging, different chiplets are interconnected horizontally through interposers, with three main materials are being considered: silicon (Si), organic, and glass. Silicon interposers are the industry standard for high-performance computing (HPC) due to their ability to support fine routing, but their high cost and packaging area limitations are challenges.
To mitigate these, localized Si bridges are emerging as a solution. Organic interposers offer a cost-effective alternative, particularly through Fan-Out Panel Level Packaging (FOPLP), which increases area utilization and lowers costs by up to 60%. However, achieving fine routing similar to silicon remains difficult.
Glass interposers, with their tunable coefficient of thermal expansion (CTE) and high dimensional stability, also support panel-level packaging and cost reduction. Yet, despite their promise, glass interposer production is still maturing, limiting large-scale adoption. As the ecosystem evolves, each material brings its strengths and challenges to 2.5D packaging, focusing on balancing performance and cost.
Generally, when selecting next-generation materials for interposers in 2.5D semiconductor packaging, five key criteria are essential: dielectric constant (Dk), elongation to failure, coefficient of thermal expansion (CTE), Young’s modulus, and moisture absorption.
A low Dk is crucial to reduce capacitance and enable higher data rates, improving signal integrity. Elongation to failure ensures the material withstands mechanical stress during manufacturing. Matching the CTE of the dielectric to copper layers enhances package reliability.
On the other hand, Young’s modulus is also a key factor. While a low Young’s modulus minimizes stress on microvias, which is crucial for advanced designs with sub-5 µm vias, a higher modulus offers better stability for the package. Therefore, finding the right balance between these opposing requirements is essential for advanced packaging.
Finally, low moisture absorption is critical for long-term reliability, as excessive moisture can lead to delamination and degrade both mechanical and electrical performance. Balancing these parameters is vital for optimizing bandwidth and power efficiency in next-generation interposer materials.
Cu-Cu hybrid bonding manufacturing
Wafer-to-Wafer (W2W) and Die-to-Wafer (D2W) hybrid bonding are two key approaches for 3D hybrid bonding, each with distinct advantages and challenges. W2W bonding, the more established process, involves bonding two full wafers, typically in a single, uniform step.
This approach benefits from consistent surface area, making alignment and bonding relatively straightforward. With wafers always maintaining a round shape, the process can be optimized for high throughput, making it suitable for large-scale production. However, W2W bonding is less flexible in handling different chip sizes and is limited by the need to bond identical wafers.
On the other hand, D2W hybrid bonding is more complex and addresses the limitations of W2W when dealing with high-performance dies of different sizes. Instead of bonding entire wafers, D2W involves the precise bonding of individual dies onto a target wafer, enabling the integration of different die sizes and types in a single package. This flexibility makes D2W bonding ideal for advanced packaging techniques like chiplet integration, allowing manufacturers to mix and match dies with different functions.
However, D2W presents significant manufacturing challenges. D2W demands ultra-clean, particle-free surfaces and precise alignment, as any contamination or misalignment can lead to defects, significantly compromising bonding qualities.
Additionally, D2W bonding introduces complications with die aspect ratios. Dies with higher aspect ratios can cause unilateral bonding issues, where the bond front starts along one side, potentially leading to a scaling effect. The use of flexible organic carriers or adhesives during dicing further complicates the process. Moreover, D2W bonding is more sensitive to queue times, which can degrade surface quality before bonding occurs.
Despite these challenges, D2W bonding’s flexibility and precision are increasingly critical for high-performance applications, while integrated hybrid bonding tools are emerging to address many of these hurdles.
IDTechEx’s report, “Materials and Processing for Advanced Semiconductor Packaging 2025-2035: Technologies, Players, Forecasts”, leverages their in-depth knowledge and experience in advanced semiconductor packaging. It provides valuable insights into the materials and processing techniques employed in advanced semiconductor packaging, catering to industry professionals seeking informed perspectives on the subject matter.
Technology trends in materials and processing
This report begins by introducing readers to the fast-growing field of advanced semiconductor packaging. It lays a solid foundation for the subsequent chapters, which delve into the crucial technologies of advanced semiconductor packaging in detail.
In the next chapter, the report emphasizes the importance of performance evaluation in advanced semiconductor packaging. It explores how fabrication processes and materials directly impact the overall effectiveness of the packaging.
The chapter specifically examines the 2.5D packaging process flow, with a focus on essential materials and technologies, including dielectric materials (Inorganic such as Si and Glass, as well as organic materials) for Redistribution Layer (RDL) and Microvia, RDL fabrication techniques, and the choices of materials for Epoxy Molded Compounds (EMC) and Mold Under Fill (MUF). Every sub-section within this chapter encompasses a comprehensive analysis of fabrication process flows, technology benchmarks, player evaluations, and identification of future technology trends.
Transitioning from 2.5D packaging, the subsequent chapter directs attention to the pioneering Cu-Cu hybrid bonding technology for 3D die stacking. This section provides valuable insights into the manufacturing process and bonding equipment of Cu-Cu hybrid bonding, offering guidance on material selection for optimal outcomes. Moreover, the chapter presents engaging case studies that showcase the successful implementation of Cu-Cu hybrid bonding using both organic and inorganic dielectrics.
Market forecast
The report includes a 10-year market forecast for the Organic Dielectric Advanced Semiconductor Packaging Module, presenting projections for both unit and area metrics. It offers insights into the anticipated market growth and trends over the next decade.