Systematic low-temperatue bonding and its application to the hydrogen ion cut process and three-dimensional structures

A systematic low temperature process is demonstrated in this work. This process is improved from the earlier wafer bonding technology. It can be reproduced consistently therefore it can be implemented in the modern semiconductor industry to produce three-dimensional structures. Three-dimensional electronic devices are considered the next generation in the IC industry. Low temperature bonding technology is a necessary approach to produce this multi-layer, multi-function electronic device. To stack the electronic devices, as well as vertical integration of different other microstructures, such as III--V based photo-electro devices, microwave devices and Micro-Electro-Mechanical-Structure (MEMS), into one single silicon based IC chip, to achieve so-called system-on chip structure, is critical for the further development of the ultra-large-scale-integration (ULSI) technology. Some necessary approaches, such as systematic low temperature wafer bonding, reversible bonding, layer splitting and thin film transferring, copper to copper low temperature direct bonding, etc. are demonstrated, in order to make it possible for the vertical integration. Low temperature direct bonding together with reversible bonding, are the key steps to stack different pre-fabricated active device layer into one single chip. Ion-cut technology, also referred as Smart-cutRTM technology, demonstrated a excellent way to form thin films that can be further processed in the conventional IC microfabrication laboratory. The development of this technology, especially using boron and hydrogen co-implantation instead of using hydrogen implantation only, as of the conventional Smart-cutRTM technology, reduced both the implantation dose and the cutting temperature to an acceptable level for the active device layer. Cu to Cu low temperature direct bonding technology may be critical in some of the ULSI applications. An easy way of Cu-Cu low temperature bonding is demonstrated in this work. Following the summary, some further work also critical for the vertical integration is discussed, such as the thin film transfer, or so-called low temperature modular lift-off technology, the possibility of implementing B-H co-implantation layer splitting in partially or fully processed device layers, etc.