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The current state of Hybrid Bonding in 2026 — TSMC sits at 6 microns and the HBM delay that nobody expected
Copper-to-copper stacking is in volume on logic, but the memory payday has slipped to the end of the decade.
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Hybrid bonding, the copper-to-copper joining technique that replaces solder microbumps in 3D chip stacks, is in high-volume production on logic chips and has just been postponed for use with memory. TSMC has scaled its SoIC bond pitch from 9 microns to 6 and laid out a path to 4.5 by 2029; Intel began shipping Foveros Direct hybrid bonding in its Clearwater Forest server CPU in the first half of 2026, and AMD has used the technology in volume since the first 3D V-Cache parts. However, a JEDEC decision earlier this year to raise the HBM stack-height limit lets HBM4 stay on the less sophisticated and expense microbump technology, deferring hybrid bonding's arrival in high-bandwidth memory, and is now set to debut in HBM4E and HBM5 at the end of the decade.
The technique works by polishing two dies flat, then bonding their copper pads and surrounding dielectric directly under heat and pressure, with no solder bump in between. Because there’s no bump to collapse, the connections can be packed far tighter. AMD has cited roughly 15 times the interconnect density of conventional 2.5D microbump stacking, and figures presented at TSMC's 2026 technology symposium put face-to-face hybrid bonding at around 14,000 signals per square millimeter against roughly 1,500 for face-to-back through-silicon-via stacking.
Microbumps have historically run at pitches around 40 microns, tightening toward 10 for the latest memory. Hybrid bonding, however, starts where microbumps end and keeps scaling: the leading edge is at 6 microns now, with 4.5- and 3-micron generations in development and sub-micron pitches demonstrated in research. Each step down multiplies the number of vertical connections between stacked dies, allowing a cache die or a compute tile to behave as if it were part of the chip rather than a separate component wired across a package.
The method is split into two different approaches: wafer-to-wafer and die-to-wafer. Wafer-to-wafer bonding joins two full patterned wafers face-to-face and dices them afterward, which allows the tightest pitch and fastest production because alignment happens once at the wafer scale. Imec and EV Group demonstrated a 200-nanometer wafer-to-wafer pitch with post-bond overlay below 40 nanometers at ECTC in May. The constraint here is that both wafers must carry identically sized dies, and every die gets bonded, including defective ones, so a single bad die on either wafer ruins the pair.
In contrast, die-to-wafer bonding places individual, pre-tested dies onto a wafer — which is what chiplet and HBM stacks require — because it allows known-good-die selection and the mixing of different die sizes and process nodes. There’s a penalty in terms of throughput with die-to-wafer as each die is picked, aligned, and placed in sequence rather than in one wafer-scale step.
The best die-to-wafer pitch shown at ECTC 2026, from CEA-Leti, was 1 micron, roughly five times looser than the wafer-to-wafer record. Because the dies are placed one at a time, the speed the bonder runs at sets the limit on how many chips it can produce. Applied Materials and Besi cite around 1,600 die placements per hour on the Kinex platform, and Besi's Chameo bonders are rated near 2,000 chips per hour, with the next generation aiming for 50-nanometer placement accuracy to reach finer pitches.
Hybrid bonding is difficult to achieve, as two surfaces have to be almost perfectly flat and clean. The dielectric holds on contact through van der Waals forces, so the polished surface can vary by no more than around 0.2 nanometers, and the copper pads have to sit a few nanometers below it, close enough that they swell into contact when the stack is heated to 200 to 300℃. A single particle smaller than a micron holds the surfaces apart and lea