Investigative characterization of delamination at TiW-Cu interface in low-temperature bonded interconnects

• Published in: Materials characterization 2024-03, Vol.209, p.113772, Article 113772
• Main Authors: Golim, Obert, Vuorinen, Vesa, Ross, Glenn, Suihkonen, Sami, Paulasto-Kröckel, Mervi
• Format: Article
• Language: English
• Subjects: Delamination; Interconnect; Interface; SLID
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2024.113772

The trend for heterogeneous integration has driven the need for a low-temperature bonding process. Cu-Sn-In based solid-liquid interdiffusion (SLID) bonding technology has been presented as a viable option. However, previous studies have also reported that issues might exist in the interconnect interface towards the substrate, leading to the formation of intermetallic layers at undesired locations. This study carried out a series of characterization methods to determine the root cause of this issue. Cross-sectional observations showed that the problem occurs particularly at the TiW-Cu interface. Examination of the adhesion layer showed possible impurities existing in the layers, compromising its adhesion to copper. Residual stress analyses displayed opposing loading conditions at the interface. The interplay of the two factors resulted in the delamination of the TiW-Cu interface, leading to a pathway for SnIn atoms. Furthermore, several methods are proposed to mitigate this issue. [Display omitted] •The interconnect was fabricated at bonding temperature of 170 °C.•The bonding process utilizes Cu-Sn-In based solid-liquid interdiffusion method.•A series of characterizations determine the root cause of failure at TiW-Cu interface.•Impurities were studied by time-of-flight elastic recoil detection analysis method.•Residual stresses are among the major causes for defect formation.