Thermomechanical stress and deformation effects in reactive Al/Ni multilayers for debonding

第一个项目阶段旨在确定机械和热机械应力以及约束对Ni/Al多层膜的相变反应和相形成的影响。这包括机械载荷引起的内应力和外应力，以及几何约束引起的应力，如多层膜上的钝化层。到目前为止，外加应力对Al/Ni反应性多层膜体系的反应行为及其相的形成没有明显的影响。然而，在研究中发现，在反应之后/在反应过程中，对于某些衬底，特别是在单晶硅上，RMS会发生裂纹形成或分层。此外，反应速度和温度也是以这种方式改变的。因此，反应过程中和反应后的内部热机械应力比外部应力重要得多。下一个项目阶段将考虑这些本征应力，并旨在利用这些本征应力对薄膜进行选择性分层，因此，必须表征相应的热机械性能，并为脱粘工艺量身定做。在微系统技术领域，脱粘和分层应用对于拆卸和回收是极其重要的。个别部件只能很难或不经济地从整个系统中分离出来，因此可以更换，这严重损害了可持续性和循环经济(资源节约)。在应用领域，将RMS集成到微电子系统中将是必要的。除了应力引起的分层外，还需要对其长期稳定性进行详细的研究。RMS的老化是否发生，以及RMS可以在系统中保持活跃的时间-温度机制，即保持自传播高温合成。此外，在这种情况下，RMS可以被视为功能连接，其需要测量层结构的热导率和电导性、机械性能以及在连接过程中与低熔点焊料(电镀或磁控溅射)或单独添加的连接连接的兼容性。随后，将研究与低熔点焊料的兼容性(连接部分)。最后，将对整个系统的可靠性和可行性进行调查。

The first project phase aimed at identifying the effects of mechanical and thermomechanical stresses and constraints on the transformation reaction and phase formation in Ni/Al multilayers. This included intrinsic and extrinsic stresses resulting from mechanical loading as well as stresses caused by geometrical confinements, such as passivation layers on multilayer films. So far, it could be shown that extrinsically applied stresses have no significant influence on the reaction behavior of the Al/Ni reactive multilayer system (RMS) and their phase formation. During the investigations, however, it was shown that after/during the reaction, crack formation, or delamination of the RMS takes place for certain substrates, especially on single-crystalline silicon. In addition, the reaction speed and temperature was changed that way. Thus, the intrinsic thermomechanical stresses during and after the reaction are much more important than extrinsic stresses. The next project phase will consider these intrinsic stresses and aims to exploit these intrinsic stresses for selective delamination of the films "at the push of a button", Therefore, the corresponding thermomechanical properties have to be characterized, and the tailored for debonding processes. Debonding and delamination applications are extremely important for dismantling and recycling in the field of microsystem technology. Individual components can only be separated from the overall system with difficulty or not economically and can thus be replaced, which strongly impairs sustainability and circular economy (resource saving). In the field of application, the integration of the RMS into a microelectronic system will be necessary. Besides the stress-induced delamination, detailed investigations of the long-term stability are necessary. Does aging of the RMS takes place and which time-temperature regimes the RMS can remain active in the system, i. e. maintain a self-propagating high-temperature synthesis. Furthermore, the RMS can be regarded as a functional connection in this case, which entails measurements of the thermal as well as electrical conductivity, mechanical properties of the layer structure as well as the compatibility in the context of a joining connection with low-melting solders (deposited galvanically or by magnetron sputtering) or separately added during the joining process. Subsequently, compatibility with low-melting solders will be investigated (joining part). It is further investigated whether ideally a second RMS can be used for the joining process Finally, investigations will be carried out on the complete system with regard to reliability and feasibility.