As SK hynix, which has raced ahead by taking the lead in the high-bandwidth memory (HBM) market, enters the sixth-generation HBM "HBM4" era, concerns are emerging that it faces structural limits. Scholars and industry experts worry that the company's adherence to a "foundry outsourcing model" and "process conservatism" could become weaknesses in the era of customized artificial intelligence (AI) chips.
In fact, on the 12th, Samsung Electronics began the world's first mass production and shipment of HBM4, moving to reclaim leadership by achieving an industry-best operating speed of up to 13 Gbps.
Starting with HBM4, not only the stacked memory dies but also the performance and design of the bottom "logic die (base die)" are becoming decisive factors for overall system computing efficiency. Academia characterizes this as the "system semiconductor-ization of memory," in which memory goes beyond simple storage to perform compute-assist functions.
SK hynix's decision not to produce logic dies in-house and to rely on TSMC is a strategic choice driven by the lack of foundry infrastructure. The issue is control. Because SK hynix must align its design (DTCO) to TSMC's process platform, the efficiency of integrated design between memory and logic inevitably suffers. Analysts also say a structure in which core design data is shared with an external foundry will be a strategic burden over the long term. In contrast, Samsung Electronics can optimize charge transport paths and wiring as if they were a single body through a vertically integrated structure spanning memory, foundry, and packaging.
The absence of a foundry for the logic die has led to different DRAM process choices. While Samsung Electronics, leveraging its in-house foundry design, swiftly deployed one-generation-ahead 1c (sixth-generation) DRAM, SK hynix opted for a conservative strategy, applying existing 1b (fifth-generation) DRAM to initial volumes for Production yield stability.
The 1c process far surpasses 1b in density and power efficiency. With "power" and "heat" the top concerns in AI data centers, the prevailing view is that the 1b process has reached its physical limits for achieving the ultra-high speeds of 13 Gbps and above demanded by Nvidia. For SK hynix, which cannot directly control logic-die design and thermal architecture, pushing performance higher can cause heat to climb steeply and undermine product stability. In addition, the 1c process reduces chip area to increase the number of net dies per wafer, raising the possibility that SK hynix could fall behind in cost competitiveness and future profitability.
TSMC's leading-edge process and advanced packaging (CoWoS) capacity—key to HBM4 production—are currently monopolized by global big tech. For SK hynix, this creates an unstable situation in which its product supply depends on securing TSMC's production slots. This also hampers agile responses to customer-specific spec changes. Moreover, as U.S.-China tensions and cross-strait strains rise, SK hynix's supply chain, with 100% dependence on TSMC, becomes exposed to uncertainty.
While the Production yield competitiveness SK hynix demonstrated up to HBM3E (fifth-generation HBM) is highly regarded, HBM4 is a "system integration" competition, not simple manufacturing. That is because foundry control and the timing of adopting leading-edge DRAM processes are directly tied to performance scalability.
In response, SK hynix said, "Applying 1bnm to the core die and TSMC's leading-edge process to the base die is intended to build a mass production system that meets customer needs by securing stable Production yield based on an existing platform, and we will further strengthen collaboration with partners that have top-tier competitiveness in the industry."
A semiconductor expert who requested anonymity said, "Starting with HBM4, gaps in technology on the logic die widen, and unless SK hynix makes its foundry-dependent structure independent, competing with Samsung may become increasingly difficult," adding, "Since it is hard for TSMC to drop everything and go all-in on SK hynix, the company is inherently more vulnerable than Samsung, which develops foundry and logic dies in-house and pushes high-spec products."