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Cu-Cu hybrid bonding for high-bandwidth memory (HBM)

By John H. Lau [Unimicron Technology Corporation]
H y b r i d b o n d i n g h a s by Yangtze Memory Technologies mentioned in [2], Samsung has been

achieved quite a bit of
NAND flash memory [1,2,7,8].
its high-bandwidth memory (HBM)
t r a ct ion re cently. For Company Ltd. (YMTC) on its 3D in production for 3D-IC integration of
example, the 2023 IEEE Electronic The brief fundamentals and recent by f lip - ch ip h ig h-bondi ng force
C o m p o n e n t s a n d Te c h n o l o g y a d v a n c e s a n d t r e n d s of C u - C u thermocompression bonding (TCB)
Conference (ECTC) featured more than bumpless hybrid bonding from the of the C2 (Cu-pillar with solder cap
80 papers related to hybrid bonding. IEEE/ECTC 2022 papers and IEEE/ or µbump) TSV (through-silicon via)
In [1,2], it was mentioned that Cu- ECTC 2023 papers have been reported, chips with nonconductive film (NCF).
Cu bumpless hybrid bonding, i.e., so- respectively in [1,2] and [7,8]. The Figure 1a schematically shows the
called direct-bond interconnect (DBI), recent advances and trends of Cu-Cu 16H multi-stack using the flip-chip
was invented by the Research Triangle hybrid bonding for high-bandwidth TCB solder reflow method. It can be
Institute (RTI) in the U.S. [3-6] around memory (HBM) will be discussed in seen that there are joint gaps between
2000. At about the same time, Suga this technology review. the chips. However, with HCB, the
and his colleagues in Japan proposed chips are bumpless and the Cu-pad
a similar technology called room- Samsung’s hybrid bonding for HBM to Cu-pad pairs are bonded with
temperature bumpless direct bonding D u r i ng I EEE / EC TC ( M ay 30 - die-to-wafer (D2W) and die-to-die
[7-10]. DBI has been in very high- June 2, 2023), Samsung published (D2D) methods [1,2,7,8]. Figure 1b
volume manufacturing since 2016 by at least 6 papers on hybrid bonding. schematically shows the 16H multi-
Sony on its complementary metal- In [11], they presented a multi-stack stack using the HCB method. It can be
oxide-semiconductor (CMOS) image hybrid Cu bonding (HCB) technology seen that the total package thickness
sensors (CIS) [1,2,7,8], and since 2021 development using ultra-thin chips. As is smaller than the one using the TCB

Figure 1: 16H HBM structure: a) Flip chip with microbump solder reflow with joint gap; b) D2W/D2D Cu-Cu hybrid bonding with gapless joint. SOURCES: [7,11]

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