With the continuous scaling of semiconductor technology, the performance of integrated circuits (ICs) has improved significantly. However, as the feature size of ICs shrinks, the resistance-capacitance (RC) delay of the back-end-of-line (BEOL) interconnects has become a bottleneck in the performance of ICs. To overcome this limitation, the development of ultralow-k dielectrics has become a key focus of research in recent years.

An ultralow-k dielectric has been fabricated with structured cylindrical pores that can effectively mitigate the temperature rise of the interconnect and improve interconnect reliability. We build upon the work of previous research by using carbon nanotubes (CNT) as a template to form a porous dielectric with vertically aligned cylindrical pores...[ Read more ]

With the continuous scaling of semiconductor technology, the performance of integrated circuits (ICs) has improved significantly. However, as the feature size of ICs shrinks, the resistance-capacitance (RC) delay of the back-end-of-line (BEOL) interconnects has become a bottleneck in the performance of ICs. To overcome this limitation, the development of ultralow-k dielectrics has become a key focus of research in recent years.

An ultralow-k dielectric has been fabricated with structured cylindrical pores that can effectively mitigate the temperature rise of the interconnect and improve interconnect reliability. We build upon the work of previous research by using carbon nanotubes (CNT) as a template to form a porous dielectric with vertically aligned cylindrical pores on a Si₃N₄ etch stop layer, which is then integrated with the Cu damascene process.The resulting cylindrical porous dielectric possesses an anisotropic dielectric property, with a large inter-layer dielectric constant of 1.97 and a small intra-layer dielectric constant of 1.75. The high elastic modulus of 15.7 GPa is maintained, making it a promising candidate for extending the scaling of low-k dielectrics.

However, this technology faced reliability issues, which were addressed in this thesis.

The CNT fabrication process is developed and optimized to form a uniform and high-quality CNT. Different capping layers like Si₃N₄ and hBN are studied to reduce the surface roughness of low k. The results proved that Si₃N₄ can’t be used to reduce the surface roughness, however the use of thin film of hBN significantly reduced the surface roughness of low k dielectric with strong adhesion forces with the dielectric surface and a thicker hBN layer makes the surface smoother than a thin one. In addition, hBN increase the water contact angle of low k dielectric as a hydrophobic capping layer. Finally, copper diffusion is very serious in porous dielectric and the results showed that the use of hBN as a copper diffusion barrier abruptly reduced copper diffusion and using a thick hBN layer completely prevents copper to penetrates the low k dielectric.