Lin Po-Fan, Tran Dinh-Phuc, Liu Hung-Che, Li Yi-Yi, Chen Chih
Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.
Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan.
Materials (Basel). 2022 Jan 26;15(3):937. doi: 10.3390/ma15030937.
Copper-to-copper (Cu-to-Cu) direct bonding is a promising approach to replace traditional solder joints in three-dimensional integrated circuits (3D ICs) packaging. It has been commonly conducted at a temperature over 300 °C, which is detrimental to integrated electronic devices. In this study, highly (111)-oriented nanotwinned (nt) Cu films were fabricated and polished using chemical mechanical planarization (CMP) and electropolishing. We successfully bonded and remained columnar nt-Cu microstructure at a low temperature of 150 °C thanks to the rapid diffusion of Cu on (111) surface. We employed a new microstructural method to characterize quantitatively the interfacial bonding quality using cross-sectional and plan-view microstructural analyses. We discovered that CMP nt-Cu bonding quality was greater than that of electropolished nt-Cu ones. The CMP nt-Cu films possessed extremely low surface roughness and were virtually free of pre-existing interface voids. Thus, the bonding time of such CMP nt-Cu films could be significantly shortened to 10 min. We expect that these findings may offer a pathway to reduce the thermal budget and manufacturing cost of the current 3D ICs packaging technology.
铜对铜（Cu-to-Cu）直接键合是一种很有前景的方法，可用于替代三维集成电路（3D IC）封装中的传统焊点。它通常在超过300°C的温度下进行，这对集成电子器件不利。在本研究中，通过化学机械平面化（CMP）和电化学抛光制备并抛光了高度（111）取向的纳米孪晶（nt）铜膜。由于铜在（111）表面上的快速扩散，我们在150°C的低温下成功键合并保留了柱状nt-Cu微观结构。我们采用了一种新的微观结构方法，通过横截面和平面微观结构分析来定量表征界面键合质量。我们发现CMP nt-Cu的键合质量优于电化学抛光的nt-Cu。CMP nt-Cu膜具有极低的表面粗糙度，并且几乎没有预先存在的界面空隙。因此，此类CMP nt-Cu膜的键合时间可显著缩短至10分钟。我们期望这些发现可能为降低当前3D IC封装技术的热预算和制造成本提供一条途径。
