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growth occurring across the bonding
interface. However, there are some
challenges of hybrid bonding for
HBM as pointed out by Micron [14]
and are discussed below.
P a r t i c l e s g e ne r at e d b y
conventional wafer dicing. Figure
10 shows the particle counts before
a nd af ter a laser stealt h dici ng,
classifications of dicing particles,
and signatures of particles. Micron
fo u n d t h a t l a s e r s t e a lt h d ic i n g
(Figure 10b) generated far more
particles than that allowed by a Cu
hybr id bondi ng process (Figure Figure 7: Bonding strength and SAM images of samples under plasma conditions A, B, and C after end-of-line
10 a) — a n i n c r e a s e b y 7 x . T h e and reliability testing. SOURCES: [7,13]
dicing particles can be classified
as inorganics such as silicon dust
(Figure 10c), and organics such as
tape residues (Figure 10d). Both of
them have different impacts on void
formulation at the bonding interface.
The signature of particle impacts on
voids are circular shaped as shown
i n Fig ure 10e, a nd a s show n i n
Figure 10f, circular shaped attached
with a comet tail due to the bonding
wave inf luence [14]. Both organic
and inorganic particles are harmful,
but inorganic ones will generate a
much bigger void compared with
organic ones.
P a r t i c l e m i t i g a t i o n b y
combination laser grooving and
plasma dicing. Figure 11a shows a
typical memory scribe design with
five dielectric films. Micron proposed Figure 8: Thermal resistance comparison according to different structures (MUF vs. HBI). SOURCES: [7,13]
a combination of laser g rooving
plus plasma etching to achieve an
optimum balance between the dicing
quality and a reasonable throughput.
By doing this, an innovative cleaning
method to successfully remove the
debris and dust (due to lasering)
before plasma etching was developed
and the effects are shown before
cleaning in Figure 11b, and post
cleaning in Figure 11c. The post-
wafer dicing and cleaning images at
saw streets are shown in Figure 11d
at the wafer center, and in Figure
11e at the wafer edge. The overall
particle counts are shown in Figure
11f; Figures 11b-f show that the saw
streets are clean, and the particle
counts are significantly reduced.
Figure 9: a) HBM with flip-chip solder reflow (20µm pitch); b) HBM with hybrid bonding; and c) Cu crystal
growth across the bonding interface. SOURCES: [7,14]

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