Influence of Atmosphere on Ultrasonic Bonding of Silicon to Metal

对几种金属箔（Au、Ag、Al、Cu、Ni、Fe）进行了超声键合。在类似金属键合的情况下，也进行了良好的键合。然而，在异种金属结合的情况下，只有少数金属箔的组合能够实现良好的结合。金属箔与Ag箔的结合非常差。接着，检查金属箔与Si晶片的接合能力，并且用Au箔和Al箔获得良好的接合。在Si与Al箔接合的情况下，接合强度（剪切强度）存在大的分散。由于Si/Al箔键合强度的大分散可能是由键合表面上的氧化层引起的，因此将Si和Al箔浸入酸和碱中以去除氧化层。即Si在HF水溶液中浸泡24 h，Al箔在不同含量（0 ~ 10 kmol/m3）的NaOH溶液中浸泡不同时间（0 ~ 10 min）。Si在HF溶液中的浸泡对Si与Al箔的结合性能没有影响， ...更多信息 铝箔在NaOH溶液中的最小结合强度在各结合条件下均有所提高，结合强度的分散性减小。溶液中NaOH含量和浸泡时间对粘接性能无明显影响。由于通过SEM观察到在NaOH溶液中浸泡期间在Al箔的氧化层上有许多小孔，因此认为结合强度的增加是由于在超声振动期间氧化层容易从金属箔表面脱离。然后，在2 Pa的压力下进行Si与Al箔的超声键合，但是没有获得强度的增加和强度的分散性的降低。采用溅射法在Si表面形成Au膜，然后在空气气氛下将Au膜与Al箔进行键合。随着Au膜厚度的增加，键合强度增加。断裂发生在Au膜与Si衬底的界面处，结合强度取决于Au箔的强度和Si/Al界面的强度。根据这些结果，可以预期，通过Si和金属表面的表面处理，Si/金属箔接合的接合强度增加。少

Ultrasonic bonding was carried out with some kinds of foil (Au, Ag, Al, Cu, Ni, Fe). In the case of similar metal bonding, good bonding was carried out. However, in the case of dissimilar metal bonding, only a few combination of metal foil enabled good bonding. The bonding of metal foil with Ag foil was very poor. Next, the bonding ability of metal foil to Si wafer was examined and good bonding was obtained with Au foil and Al foil. In the case of bonding of Si to Al foil, there was large scatter in bonding strength (shear strength). Since large scatter in strength of Si/Al foil bonding might be caused by oxide layer on the bonding face, Si and Al foil were immersed in acid and alkali to remove oxide layer. Namely, Si was immersed in HF water solution for 24 h, and Al foil was immersed in NaOH solution of different content (0 - 10 kmol/m_3) for different times (0 - 10 min). Immersion of Si in HF solution gave no influence on bonding character of Si to Al foil, but after immersion of Al … More foil in NaOH solution, minimum bonding strength increased at each bonding condition and scatter of bonding strength decreased. There was no clear influence of NaOH content in solution and immersion time on bonding character. Since many small holes were observed on the oxide layer of Al foil during immersion in NaOH solution through SEM, it was thought that the increase in bonding strength was caused by easy detachment of oxide layer from the surface of metal foil during ultrasonic vibration. Then, the ultrasonic bonding of Si to Al foil was done under a pressure of 2 Pa, but no increase in the strength and no decrease in scatter of the strength was obtained. Au film was formed on Si surface by spattering, and then the bonding of Au film to Al foil was done under air atmosphere. The bonding strength increased with increasing thickness of Au film. The fracture occurred at an interface between Au film and Si substrate, and the bonding strength was dependent on the strength of Au foil and the strength of Si/Al interface. From these results, it was expected that the bonding strength of Si/metal foil bonding increases through surface treatment of Si and metal surface. Less