采用不同电流密度和外加剂浓度将Cu电镀填充到硅通孔(TSV)制作晶圆试样, 将试样置于Ar气环境内进行退火处理. 观测了硅通孔填充Cu (TSV-Cu)的胀出量和界面完整性, 分析了电镀参数对填充Cu微结构(晶粒尺寸)以及微结构对填充Cu退火胀出量的影响. 结果表明, 电流密度和外加剂浓度影响TSV-Cu的晶粒尺寸. 电流密度越高, 晶粒尺寸越小; 外加剂浓度越高, 晶粒尺寸越小, 但其影响程度不如电流密度显著. 退火后, Cu的晶粒尺寸变大, TSV-Cu发生胀出, 胀出量与Cu晶粒尺寸具有正相关的关系. 随着TSV-Cu的胀出, Cu-Si界面发生开裂, 裂纹沿界面层中的Cu种子层内部延伸.

3D-IC integration realized by using through-silicon via (TSV) technology is the main trend in packaging industry. TSVs are usually fully filled by electroplated Cu, namely TSV-Cu, which can make products possess higher electrical performance, higher density and lighter weight. In a typical TSV forming process, the TSV-Cu is annealed to stabilize its microstructure. However, during annealing process, the Cu protrudes out of the TSV due to the large change in temperature and the mismatch of coefficient of thermal expansion between the Cu (16.7×10^-6 ℃^-1) and its surrounding Si (2.3×10^-6 ℃^-1) matrix. This protrusion is a potential threat to the TSV structural integrity, since it might lead to cracking or delamination. In this research, the effects of annealing process on microstructure evolution and protrusion of TSV-Cu are investigated. Four level sets of current density and additive concentration were used to fill Cu into the TSV by electroplating process to prepare test specimens. The TSV diameter was 30 μm, and depth was 100 μm. The pitch of two TSVs was 200 μm. The annealing process was conducted in a vacuum annealing furnace, the specimens were heated from 25 ℃ to 425 ℃, and then maintained for 30 min at 425 ℃. The microstructures of TSV-Cu before and after annealing were characterized by EBSD. The protrusion of specimens after annealing was measured by White Light Interferometer (WLI). The results show that, during the electroplating process, both current density and additive concentration have impact on the TSV-Cu grain size, higher current density and higher additive concentration help to gain a finer grained Cu, and the influence of the additive concentration is less significant than the current density. After being annealed, for all the specimens, the Cu grain size increases, the TSV-Cu protrudes with a crack along the Cu-Si interface within the Cu seed layer, and there is a positive correlation between the protrusion and the grain size of the TSV-Cu.