Invited Paper EM-ThM1
John A. Thornton Memorial Award Lecture - PECVD Low and Ultralow Dielectric Constant Materials: From Invention and Research to Products
Thursday, October 22, 2015, 8:00 am, Room 211C
In April this year we celebrated the 50th anniversary of Moore's law which has been followed by the semiconductor industry together with Dennard's scaling law, resulting in continuously improved performance and increased density of the semiconductor microprocessors. For 22 years this was accomplished using the same material composed of Si, Al, O, N, and shrinking the dimensions of the devices. At the 0.25 mm node, the interconnect became the bottleneck to the improvement of the performance of the VLSI integrated circuits and required the introduction of new materials to reduce its RC. After the replacement of Al with the more conductive Cu in 1997, it took seven more years to replace the SiO2 insulator (k=4) of the interconnect with a low-k dielectric. While the academia and industry were aware already in the 1990s of the need for a low-k dielectric and many potential materials were developed and investigated, none could be integrated in a VLSI product requiring multiple revisions of the. The early, unsuccessful efforts were focused on polymeric or hybrid organic-inorganic films fabricated by spin-on techniques. Realizing that PECVD materials would have superior properties to those of the spin-ons, we invented, developed and characterized the carbon-doped oxide SiCOH, deposited by PECVD, obtaining a material with a dielectric constant k=3 which was successfully integrated in VLSI products starting at the 90 nm node and became the industry standard as the interconnect dielectric. This development has continued with the invention of porous pSiCOH ultralow-k (ULK) dielectrics with further reduced k values. pSiCOH with k as low as ~2 was demonstrated in research lab and a materials with k=2.4 was successfully implemented in products at the 45 nm node, to maintain a reduced capacitance for the scaled dimensions of the shrunken technology nodes.
The talk will discuss the development and optimization of the PECVD SiCOH and pSiCOH dielectrics, integration issues related to these materials of reduced mechanical and chemical properties compared to SiO2, understanding the correlation between process parameters, dielectric characteristics and the reliability of the integrated interconnect, and the current state of the art of the interconnect dielectrics which enabled the continuation of Moore's law into nanoscale dimensions.