[News] The Era of Heterogeneous Integration Approaches: Who Shall Dominate the Advanced Packaging Field?

2024-03-18 Semiconductors editor

“It is not the shortage of AI chips, it is the shortage of our CoWoS capacity,” replied TSMC Chairman Mark Liu during an interview in September last year, propelling this technology that TSMC had quietly cultivated for over a decade into a global spotlight.

As per a report from TechNews, the hardware demand sparked by generative AI has also led to “advanced packaging” becoming not only a hot keyword pursued by global investors but also a prominent feature of the semiconductor industry. From foundries and memory manufacturers to OASTs, all are actively involved in the research and capacity expansion of advanced packaging technologies.

TSMC, the leading force in the advanced packaging market, has repeatedly emphasized its efforts to expand capacity during its earnings call, including capacity expansions in Zhunan and Hsinchu, and even the possibility of constructing advanced packaging facilities in Chiayi.

Intel’s strategic moves also underscore its emphasis on the development of advanced packaging. Intel’s new plant completed in Penang, Malaysia in 2023 is aimed at establishing advanced packaging capacity.

Leading packaging and testing company, ASE Technology Holding, has also actively participated in the competition for advanced packaging. Apart from its subsidiary, Siliconware Precision Industries (SPIL), which is already a supplier for the backend packaging of CoWoS, ASE Technology Holding is also expanding advanced packaging capacity at its facility in Kaohsiung.

Memory manufacturers are also aggressively ramping up their advanced packaging capacity. SK Hynix, which exclusively supplies HBM for NVIDIA AI chips, recently announced plans to invest USD 1 billion in the development of advanced packaging. They view advanced packaging as the “future focus of semiconductor development for the next 50 years.

Advanced Packaging: Over a Decade of Development

In fact, advanced packaging is not a new concept. Tracing the history of packaging technology, the year 2000 undoubtedly marked a turning point. From this year onwards, packaging technology shifted from traditional wire bonding and flip-chip methods to “wafer-level packaging,” where most or all packaging and testing processes are conducted on the wafer itself.

The 2.5D packaging, which gained significant attention after 2023, actually emerged as early as 2010. However, due to cost concerns, the number of manufacturers adopting this technology was relatively limited, with a focus on high-performance computing chips.

Chiang Shang-yi, the Chief Strategy Officer of Foxconn Semiconductor, recalled the initial lack of interest in CoWoS technology, which even led to him being regarded as a “joke” within the company( TSMC) for proposing advanced packaging. He also revealed that the first company willing to adopt the costly CoWoS technology was actually Huawei.


▲ Semiconductor Packaging Technology Evolution compiled by McKinsey, Accelerated Technological Evolution after 2000 (Source: McKinsey)

Compared to 2D packaging technology, 2.5D packaging involves placing an intermediate layer between the chip and the IC substrate and stacking different chips in parallel. TSMC’s CoWoS has become synonymous with 2.5D packaging, where a silicon interposer layer is inserted between the chip and the SiP substrate, and metal layers are connected using Through-Silicon Vias (TSVs) to overcome the density limitations of SiP substrates, which previously restricted the number of chips.

Despite TSMC’s dominance, Intel, with its extensive technical expertise in CPU packaging, cannot be underestimated. In the 2.5D packaging battlefield, Intel employs EMIB technology as its strategy. Unlike CoWoS, EMIB does not utilize a silicon interposer layer.

Instead, its key feature lies in the “Silicon Bridge,” buried within the packaging substrate, which connects the bare dies. Intel believes that EMIB offers cost advantages compared to solutions using large silicon interposer layers.

In recent years, Samsung, which has been actively cultivating the semiconductor foundry market, has also ventured into the 2.5D packaging arena. Their proprietary I-Cube technology has traditionally targeted applications in High-Performance Computing (HPC) chips. When Samsung introduced I-Cube4 in 2021, it emphasized the integration of multiple logic dies and HBM placed on a silicon interposer layer, enabling heterogeneous integration into a single chip.

As Moore’s Law approaches its limits and the massive computational demands triggered by generative AI continue to surge, coupled with the trend towards lighter, thinner, and smaller end products, chips are inevitably evolving towards more transistors, greater computational power, and lower power consumption performance.

Therefore, the transition of packaging technology from 2.5D to 3D is undoubtedly an inevitable development.

The difference between 3D and 2.5D packaging lies in the stacking method. In 2.5D packaging, chips are stacked parallelly on an intermediate layer, while in 3D packaging, chips are stacked vertically in a three-dimensional manner.

The advantage of 3D packaging lies in its ability to create more space for transistors within a chip through stacking, shorten the distance between different bare dies significantly, enhance transmission efficiency, and reduce power consumption during transmission.

TSMC, Intel, and Samsung Racing for 3D Packaging Technology

TSMC’s positioning in 3D IC technology is undeniable. Its SoIC technology adopts the wafer-to-wafer bonding technique. SoIC integrates homogeneous and heterogeneous small dies into a single chip, with smaller dimensions and a thinner profile. It can be integrated into 2.5D CoWoS or InFO. From an external perspective, SoIC resembles a universal SoC chip but integrates various functions heterogeneously.

Intel’s layout in 3D packaging revolves around its 3D Foveros technology. Structurally, the bottom layer comprises a packaging substrate, with a bottom wafer placed on top serving as an intermediate layer. Within this intermediate layer, numerous TSVs (Through-Silicon Vias) are present, facilitating connections between the upper chips, modules, and other parts of the system to achieve transmission purposes.

Samsung’s X-Cube 3D packaging technology utilizes TSV processes. Currently, Samsung’s X-Cube test chips can stack the SRAM layer on top of the logic layer, interconnected via TSVs, employing its 7nm EUV process technology.

TSMC’s Comprehensive Ecosystem Strategy

Currently dominating the advanced packaging market, thanks to its acquisition of large contracts for manufacturing NVIDIA AI chips, TSMC is not only continuing to develop more advanced packaging technologies but is also actively promoting its 3D Fabric platform.

In addition to incorporating the three key packaging technologies CoWoS, InFo, and SoIC, this platform has expanded into an industry alliance. It includes participation from EDA, IP, DCA/VCA, memory, packaging and testing suppliers, as well as substrate and testing vendors. The goal is to create a complete 3D Fabric ecosystem, strengthen innovation, and enhance customer adoption willingness.

This alliance has attracted active participation from heavyweight players in the semiconductor upstream supply chain. Even companies traditionally seen as competitors in the packaging and testing sector, such as Amkor, ASE Technology Holding, and Siliconware Precision Industries (SPIL), are members. The comprehensive supply chain has become a significant advantage for TSMC in providing advanced packaging contract manufacturing services.

▲ TSMC’s 3D Fabric Alliance members, including major players from EDA to packaging and testing companies. (Image Source: TSMC)

In comparison, Intel, despite its robust technological expertise developed over many years and its proposition to independently provide wafer manufacturing or testing services, faces a disadvantage in expanding its market share in advanced packaging due to its lack of experience in the foundry market.

On the other hand, Samsung, compared to TSMC, is constrained by its yield issues in advanced processes. This limitation leads IC design companies to prioritize foundries with more stable yields when considering outsourcing comprehensive manufacturing services.

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(Photo credit: TSMC)

Please note that this article cites information from TechNews.