AI has been propelled to new heights by HBM1, the ultra-fast DRAM which has continually pushed the technical limits of memory. Some may therefore consider HBM to be an overnight success linked with the recent rise of generative AI. However, it is actually the culmination of a semiconductor technology revolution that took over a decade of hard work and collaboration involving numerous technical experts.
1HBM: A high-value, high-performance product that revolutionizes data processing speeds by connecting multiple DRAM chips with through-silicon via (TSV).
Since developing the world’s first HBM in 2013, SK hynix has led the way in developing the next generations of the technology. In March 2024, the company became the first to mass-produce and supply HBM3E, the fifth generation of HBM which offers the industry’s highest levels of performance.
SK hynix’s leadership in this area is due to its extensive history of preparing key packaging technologies such as TSV and MR-MUF2. To find out more, the SK hynix Newsroom caught up with Gyujei Lee, head of Package Product Development, to discuss the company’s technological innovations in packaging for AI memory.
2Mass Reflow-Molded Underfill (MR-MUF): A process involving injecting a liquid protective material between stacked chips, which is then hardened. Compared to the traditional method of placing film-like materials between each layer, MR-MUF is a more efficient process and more effective at heat dissipation.
Lee cites the importance of SK hynix’s innovative packaging technologies for HBM’s success
Foundation for HBM Leadership: Bold Investment in Packaging Technology and R&D
SK hynix’s core HBM packaging technologies
SK hynix applied TSV technology to the first generation of HBM, which was developed by the company as a world-first in 2013. A key technology that enables the rapid speed of HBM products, TSV involves drilling thousands of microscopic holes in a DRAM chip to connect the electrodes that vertically penetrate the holes of the chip’s upper and lower layers.
Although TSV has been touted as a next-generation technology to overcome the performance limitations of conventional memory for more than 20 years, it did not immediately emerge as a commercialized technology. The challenges of building the technical infrastructure and the uncertainty of recouping the investment prevented companies from taking the plunge. Lee described the situation as “like a bunch of kids around a big lake, waiting to see who would jump in first.”
“SK hynix was also one of the companies to hesitate in the beginning,” he recalled. “However, to prepare for the future market, we decided to secure both TSV technology, which can simultaneously enable top performance and high capacity, and WLP3 technology, which includes stacking. Therefore, we took the initiative and began active research from the early 2000s.”
3Wafer-level package (WLP): Technology that produces end products by packaging and testing a wafer all at once before the wafer is diced. It differs from the conventional packaging method of processing a wafer and dicing each chip.
As the market for high-performance graphics processing unit (GPU) computing grew in the 2010s, there was a rising need for high-bandwidth near-memory4 to support it. To meet this demand, SK hynix began developing a new product combining TSV and WLP technologies, ultimately leading to the creation of the first HBM. This new product was more than four times faster than GDDR5, the fastest graphics DRAM product at the time, while consuming 40% less power. Moreover, the first HBM dramatically reduced the product area through chip stacking.
4Near-memory: Memory that is close to the computing device (processor), allowing for faster data processing.
From MR-MUF to Advanced MR-MUF: Driving HBM Success
Although SK hynix was the first to usher in the HBM era, the company did not take the lead in the growing market until it developed the third generation of HBM, HBM2E, in 2019. This marked a turning point for the company as it was considered to have gained a clear industry advantage. However, Lee recalls the various bumps in the road to this achievement.
Lee revealed how MR-MUF was a crucial breakthrough for the company’s HBM lineup
“We succeeded in developing the first HBM, but then we needed to raise the quality and mass production capability to a level that would satisfy the market and our customers,” he said. “This led us to develop a new packaging technology that was expected to be better than the existing one in terms of stability in material application and ease of technical implementation. But unexpectedly, we encountered reliability difficulties in the early stages and had to find a new breakthrough.
“At that time, the company was also developing MR-MUF technology according to its technology roadmap. To respond promptly to customers, leaders from the relevant departments quickly analyzed technology-related data and simulation results to verify the reliability of MR-MUF, and convinced management and customers. So, the technology was able to be applied to HBM2E in a timely manner.”
Lee cites the development of MR-MUF as a key turning point for SK hynix’s HBM success story
“Thanks to the management and customers who believed in our development team, we were able to successfully bring our unique MR-MUF technology to the market,” said Lee. “This has enabled the mass production and supply of HBM2E, which offers stable levels of quality and performance.”
Due to the application of MR-MUF, HBM2E became a game-changer in the HBM market. It is therefore clear that MR-MUF played a key role in making SK hynix’s “HBM success story” possible.
Lee explains the MR-MUF technology roadmap
In 2023, SK hynix maintained its unrivaled leadership in HBM by first developing the 12-layer HBM3, followed by the development of HBM3E, the fifth generation of HBM. Lee and the development team believe these successes were largely due to the development of Advanced MR-MUF5, an improved version of the existing MR-MUF technology.
5Advanced Mass Reflow-Molded Underfill (MR-MUF): Next-generation MR-MUF technology with warpage control that can stack chips 40% thinner than previous generations of HBM products without warpage, as well as new protective materials for improved heat dissipation.
“The 12-layer HBM3 required enhanced heat dissipation performance due to the increased number of stacked chips,” he said. “In particular, it was not easy to handle the warpage issue of the thinner chips in the 12-layer HBM3 with the existing MR-MUF method.
“To overcome these limitations, we developed an Advanced MR-MUF technology that improves on the existing MR-MUF. This also led to the successful development and mass production of the world’s first 12-layer HBM3 in 2023, followed by the mass production of the world’s highest-performing HBM3E in March 2024. Moreover, Advanced MR-MUF is applied to the 12-layer HBM3E, which will be supplied to major AI companies from the second half of this year. Going forward, Advanced MR-MUF will be applied to a wider range of applications, further solidifying SK hynix’s leadership in HBM technology.
“Recently, there was a rumor in the industry that MR-MUF is difficult to implement. To overcome this, we focused on communicating to customers that MR-MUF is the optimal technology for high stacking, and eventually reaffirmed customers’ trust.”
Next-Gen Tech & Customer Partnerships Key to Custom Product Development
Lee won SK Group’s 2024 SUPEX Award for his contribution to developing HBM
For his longstanding contributions to HBM development, Lee was awarded SK Group’s highest honor, the 2024 SUPEX Award6, in June 2024 along with SK hynix’s core HBM technical members. Commenting on receiving the award, Lee said: “It is thanks to the efforts of many members who have worked as one team to make the product a success.”
6SUPEX Award: As the most prestigious award within SK Group that carries the meaning “super excellent,” it recognizes members who have successfully realized innovations by not being afraid to take on new challenges.
However, Lee said there is no room for satisfaction or complacency. For SK hynix to maintain its HBM leadership in the future, he emphasized the importance of timely development of various next-generation packaging technologies to meet the ever-increasing demand for customized products.
“Next-generation packaging technologies such as hybrid bonding7 have recently gained attention as a way to stack chips higher for increased performance and capacity while maintaining product thickness according to standard specifications,” he stated. “Although heat control is still a challenge due to the narrower gap between the chips, these new packaging technologies are expected to solve the issue and meet the increasingly diverse performance needs of customers.
7Hybrid Bonding: A technology that connects chips together directly without bumps between them. This reduces the overall thickness of the chip, enabling high-layer stacking, and is therefore being considered for HBM products with 16 layers or more. SK hynix is currently reviewing both Advanced MR-MUF and hybrid bonding technologies.
“SK hynix will continue to enhance its existing Advanced MR-MUF with excellent heat dissipation performance, while also securing new technologies.”
Lee claimed that strong customer communication will continue to be crucial for the company’s growth
Lastly, Lee emphasized that close communication and collaboration with customers is one of SK hynix’s strengths and a competitive advantage that the company should continue to strengthen in the future.
“I think the biggest driving force behind SK hynix’s dominance in the HBM market is its ability to promptly deliver high-quality products with mass production competitiveness to customers when there was actual demand,” he said. “This has been possible not only because of our technological capabilities, but also due to our continuous communication with customers.
“Our packaging development department is also quick to identify customer and stakeholder needs and incorporate them into product features. When this effort is combined with our unique culture of collaboration, I think we’ll be a powerful force in any situation. I will continue to share my motto, ‘feel together, move vigilantly’ with our employees as we prepare for the future of SK hynix packaging.”
