THESIS
2023
1 online resource (71 pages) : illustrations (some color)
Abstract
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...[
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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 Si
3N
4 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 Si
3N
4 and hBN are studied to reduce the surface roughness of low k. The
results proved that Si
3N
4 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.
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