8 Direct Cu to Cu Bonding and Alternative Bonding Techniques …
213
Fig. 8.10 Schematic representation of coplanar, bump-less direct bonding [35]
growth occurred across the bonding interface. It is also indicated that the SAB is
less dependent on the Cu diffusion and microstructures of the Cu grains. The SAB
avoids the thermal-related issues such as thermal stress, thermal expansion, and
expansion-induced bonding misalignment.
Based on the SAB method, Suga proposed the concept of bump-less interconnect
in 2000 [35, 36], which is defined as two layer structures bonded directly with
metallic interconnections and insulating layer in a plane, as illustrated in Fig. 8.10.
The layer structures represent either combinations of LSI chip and substrate, two
different devices (RF, digital, analog, logic, memory, etc.) or wiring layer and device
layer.
Especially, this structure is expected to be applied to:
(1) Bonding of wiring layer for global interconnections and device layer on chip
(2) Improvement of yield by dividing the wiring layer
(3) Improvement of signal transmission rate by transmission line structure and
shortening distance between devices
(4) interconnecting two different device layers, such as separation of analog and
digital devices, and
(5) Bonding of optical device to Si substrate, and bonding for hetero-junction of
semiconductors [35].
Bump-less Interconnect is a generalized concept and has evolved into
“Cu/dielectric hybrid bonding” .
The SAB method demonstrated chip-scale bump-less Cu–Cu bonding interconnects of 1,000,000 electrodes at 3 μm critical dimension and 6 μm pitch, as shown in
Fig. 8.11 [4, 37]. To date, SAB has also enabled high-volume industrial applications
for metal laminates and MEMS packaging.
SAB was also modified (namely modified diffusion bonding [38] and vaporassisted SAB [39]) for Cu–Cu bonding in ambient air at 150 °C. Figure 8.12 shows
the TEM images of Cu–Cu bonding interfaces obtained with the two processes: by
using Ar beam irradiation followed by dry O 2 and humid N 2 exposure, respectively
[40, 41]. Void-free bonding with O-containing interlayer of ~15 nm thickness was
213
Fig. 8.10 Schematic representation of coplanar, bump-less direct bonding [35]
growth occurred across the bonding interface. It is also indicated that the SAB is
less dependent on the Cu diffusion and microstructures of the Cu grains. The SAB
avoids the thermal-related issues such as thermal stress, thermal expansion, and
expansion-induced bonding misalignment.
Based on the SAB method, Suga proposed the concept of bump-less interconnect
in 2000 [35, 36], which is defined as two layer structures bonded directly with
metallic interconnections and insulating layer in a plane, as illustrated in Fig. 8.10.
The layer structures represent either combinations of LSI chip and substrate, two
different devices (RF, digital, analog, logic, memory, etc.) or wiring layer and device
layer.
Especially, this structure is expected to be applied to:
(1) Bonding of wiring layer for global interconnections and device layer on chip
(2) Improvement of yield by dividing the wiring layer
(3) Improvement of signal transmission rate by transmission line structure and
shortening distance between devices
(4) interconnecting two different device layers, such as separation of analog and
digital devices, and
(5) Bonding of optical device to Si substrate, and bonding for hetero-junction of
semiconductors [35].
Bump-less Interconnect is a generalized concept and has evolved into
“Cu/dielectric hybrid bonding” .
The SAB method demonstrated chip-scale bump-less Cu–Cu bonding interconnects of 1,000,000 electrodes at 3 μm critical dimension and 6 μm pitch, as shown in
Fig. 8.11 [4, 37]. To date, SAB has also enabled high-volume industrial applications
for metal laminates and MEMS packaging.
SAB was also modified (namely modified diffusion bonding [38] and vaporassisted SAB [39]) for Cu–Cu bonding in ambient air at 150 °C. Figure 8.12 shows
the TEM images of Cu–Cu bonding interfaces obtained with the two processes: by
using Ar beam irradiation followed by dry O 2 and humid N 2 exposure, respectively
[40, 41]. Void-free bonding with O-containing interlayer of ~15 nm thickness was