BESI (BESI NA) -- Where is Hybrid Bonding Used?
In my previous article (The Bonder War – An update on ASMPT (522 HK)，BESI (BESI NA), Shibaura (6590 JP), Tazmo (6266 JP) and other advanced packaging equipment players), I discussed the various bonding (bonding) devices currently used in TSMC's CoWoS process. However, it is known that TSMC has always maintained a relatively conservative and cautious attitude towards overly advanced technologies. They prefer to let competitors go first and wait for the technology to mature before adopting it (to avoid being the first to eat crabs and stepping on pitfalls). This is reflected in the front-end process in GAA (Samsung was the first to mass-produce, TSMC will not mass-produce until 2026) and High NA EUV (Intel was the first to purchase, TSMC currently plans to mass-produce after 2030); in the back-end process, TSMC's CoWoS process has only used traditional flip-chip bonding, not the more advanced thermal compression bonding (TCB) and hybrid bonding technology already massively used by Intel. Therefore, the previous article on CoWoS only lightly touched on hybrid bonding. In this article, I will provide a more detailed introduction to hybrid bonding.
Hybrid bonding, known in the industry as the most advanced technology in advanced packaging processes, theoretically eliminates micro-bumps between chip stacks, using copper-to-copper interconnection (i.e., connecting vias with an extremely thin layer of copper pad instead of spherical bumps) to achieve direct interconnection between chips, greatly enhancing the speed of signal transmission between chips. When it comes to hybrid bonding, it's impossible not to mention BESI, a semiconductor equipment company listed in Europe -- as BESI holds a near-monopoly position in hybrid bonding equipment, the market's enthusiasm for advanced packaging over the past year has driven its stock price sky-high. There are already numerous research reports on hybrid bonding and BESI on the Street, so today, I want to take a different approach, breaking down the application of this hybrid bonding equipment from the perspective of customers and products.
First, let's systematically review from a top-down perspective which applications currently use hybrid bonding (see below chart):
The table above provides a good summary of the categories of applications for hybrid bonding (Note: the third row's fusion bonding also refers to hybrid bonding). However, it's important to note that hybrid bonding is divided into W2W (wafer-to-wafer) and D2W (die-to-wafer) types. The light blue part of the table (from CIS to the right to logic BPDN/CFET) uses W2W bonding; the dark blue part of advanced packaging uses D2W bonding. When we say that BESI has a monopoly in the hybrid bonder market, it specifically refers to its monopoly in the D2W bonding market; another semiconductor equipment company in Europe, EV Group, holds a monopoly in the W2W bonding market.
Simply put, W2W bonding, as the name suggests, bonds two types of chip wafers needed for stacking directly at the wafer level, then dices them vs. D2W bonding, which first dices the wafer of the first type of chip, then uses a pick & place method to bond the KGD (known good die) of that chip to the wafer of the second type. W2W has the advantage of lower cost and higher throughput. However, W2W's disadvantage is also very clear: since it involves bonding two wafers directly, this method only applies when the two types of chips have exactly the same size (otherwise, they won't align); another issue with wafer-level bonding is that it cannot sort out KGDs in advance. Thus, if one or both types of chips have low yield rates, the overall yield rate of W2W bonding will be very poor (i.e., a good die bonded on top of a bad die makes the entire group of bonded dies defective). Therefore, in advanced packaging processes used in logic, the industry generally uses D2W bonding (after performing KGD sorting) because the cost of scrapping an entire group of packaged dies is too high; additionally, W2W bonding has certain thickness requirements for the wafers it bonds (they cannot be too thin), which I will discuss later when talking about HBM4 hybrid bonding.
Next I will explain in details, according to the timeline listed in BESI official presentation materials, on which exact customers and chips use its D2W hybrid bonding equipment.