Investigation of the microstructural evolution and detachment of Co in contact with Cu–Sn electroplated silicon chips during solid-liquid interdiffusion bonding

Microstructural and Mechanical Characterization of Cu/Sn Slid Bonding Utilizing Co as Contact Metallization Layer

“…This study also discussed crystal orientation, structure, and the relationship between formed IMCs and bonding time and temperature [46].…”

“…As a result, utilizing Cu-Sn SLID bonding for MEMS packaging demands a physically deposited contact metallization layer/stack on the device wafers to avoid wet-process techniques (electroplating of contact metallization for Cu-Sn SLID system) [30,46]. A wide variety of chemically or physically deposited contact metallization layers (such as Cu, Ni, Ag, and Pt) have been used for Cu-Sn SLID bonding systems in the literature [30,[47][48][49][50].…”

“…Taking into account the specifically required considerations for some MEMS devices, such as CMOS compatibility, avoiding the chemical deposition on the device wafers, and chemical compatibility with the Cu-Sn SLID bonding, Co contact metallization is one of the plausible candidates [46]. In addition, it has been reported that Co can stabilize the HT-hexagonal Cu 6 Sn 5 , suppress Cu 3 Sn formation, and speed up IMC formation in the Cu-Sn SLID bonding system, which can reduce the SLID processing time and cost [46,55,56].…”

“…Taking into account the specifically required considerations for some MEMS devices, such as CMOS compatibility, avoiding the chemical deposition on the device wafers, and chemical compatibility with the Cu-Sn SLID bonding, Co contact metallization is one of the plausible candidates [46]. In addition, it has been reported that Co can stabilize the HT-hexagonal Cu 6 Sn 5 , suppress Cu 3 Sn formation, and speed up IMC formation in the Cu-Sn SLID bonding system, which can reduce the SLID processing time and cost [46,55,56]. The microstructural evolution of the Co metal in contact with Cu-Sn has been previously investigated; depending on the bonding condition, various IMCs (such as (Cu,Co) 6 Sn 5 , Cu 3 Sn, (Co,Cu) Sn and (Co,Cu)Sn 3 ) can be evolved in the joint area [46,[56][57][58].…”

“…In addition, it has been reported that Co can stabilize the HT-hexagonal Cu 6 Sn 5 , suppress Cu 3 Sn formation, and speed up IMC formation in the Cu-Sn SLID bonding system, which can reduce the SLID processing time and cost [46,55,56]. The microstructural evolution of the Co metal in contact with Cu-Sn has been previously investigated; depending on the bonding condition, various IMCs (such as (Cu,Co) 6 Sn 5 , Cu 3 Sn, (Co,Cu) Sn and (Co,Cu)Sn 3 ) can be evolved in the joint area [46,[56][57][58]. Our previous study on the microstructural evolution of the Co bulk in contact with Cu-Sn electroplated silicon chips has shown that a fully IMC-bonded joint can be successfully achieved only if a thin layer of Co (Co thickness/ Sn thickness ≤ 4%) is in contact with the Cu-Sn SLID system.…”