SK Hynix is trying to keep HBM from cooking itself as demand for AI chips drives taller, faster memory stacks.
At Hot Chips, SK Hynix VP of package engineering, Jaesik Lee, showed how the company plans to use advanced packaging to advance its HBM roadmap. The short version is that memory is getting taller, hotter and fussier, which is lovely if your hobby is thermal panic.
Current HBM stacks connect multiple DRAM core dies to a base die using through-silicon vias, or TSVs. HBM can already reach 16-Hi stacks, with 16 channels and 1,024 I/Os that link the stack to an accelerator via a silicon interposer.
The appeal is obvious enough. A GDDR6 setup can offer 24GB and 768GB/s, while four HBM3E stacks can cut space by up to half and deliver up to 144GB with 4TB/s of bandwidth.
SK Hynix’s HBM4 roadmap points to 24Gb DRAM densities, 36GB capacities, 2,048 I/O bits, up to 8Gb/s I/O speeds and 2,048GB/s bandwidth. The trade-off is a larger package, more TSVs, more micro bumps and another round of packaging grief.
The company said HBM4 brings more than 2 TB/s bandwidth, 40 per cent lower power consumption, 14 per cent better thermal resistance than HBM3E, and up to 48GB capacity. Its 12-Hi version is in production, while 16-Hi is still being qualified.
SK Hynix is already using advanced MR-MUF for 16-Hi HBM3E, with warpage control and tighter gap-fill tricks. Next comes hybrid bonding, which Lee said can deliver a 24 per cent thicker core die, a TSV pitch of less than 18 microns and 35 per cent lower thermal resistance.
The company is working on I-HBM, a local hotspot fix that puts a high-thermal-conductivity and electrically insulating cooling component near the HBM D2D PHY area. SK Hynix says that creates a dedicated heat path with more than 30 per cent extra thermal resistance reduction.
SK Hynix showed Intel’s EMIB packaging on a 2.5D HBM slide alongside CoWoS-L, CoWoS-R and CoWoS-S. The company is plainly eyeing 3D integration too, with HBM stacked on accelerators once logic and packaging tech stop looking quite so experimental.
