Invited Paper EM-WeM3
Ultralow-k PECVD pSiCOH Dielectrics and their Implementation in VLSI Interconnects

Wednesday, November 2, 2011, 8:40 am, Room 210

The performance of integrated circuits and their density has been improved continuously through the shrinking of the active devices according to Moore’s law. At the 0.25 mm technology node it became clear that new materials had to be introduced to reduce the RC of the interconnect which became a barrier to further improvement of the VLSI performance.

After IBM introduced Cu in 1997, low-k PECVD SiCOH dielectrics with a dielectric constant k=3.0 were introduced in 2003-2004 at the 90 nm node, after many other low-k dielectrics failed integration. Reduction or even maintaining of the interconnect capacitance at the decreasing dimensions of later technology nodes required the development of porous ultralow-k pSiCOH. The first generation of pSiCOH dielectrics with k=2.4 has been successfully integrated by IBM in 45 nm products, such as the Power 7 chip released in 2010. Material extendibility of porogen based pSiCOH has been demonstrated to k values as low as 2.0. However, the reduction of the dielectric constant is achieved for a given chemistry by increasing porosity in the films, resulting in a decrease of mechanical properties, degraded integrability of the dielectric, and potentially reduced reliability of the interconnect.

The original chemistry produced the pSiCOH films having a skeleton of mainly O-Si-O bonds, with nanometer sized pores stabilized by Si-CH3 groups (V1 type). These films are damaged by the integration processes and the degree of damage increases with decreasing k and decreasing pattern dimensions with each new technology node. To reduce these problems we developed pSiCOH films using precursors containing Si-CH2-Si bonds, enabling the fabrication of high-carbon (V2 type) films whose skeleton comprises Si-CH2-Si bonds in addition to the Si-O-Si. The high-carbon pSiCOH films have reduced degrees of porosity and improved pore structures as compared to the V1 type films of same k and, as a result, have higher resistance to processing damage and provide improved dimension control during integration compared to V1 pSiCOH of identical k values.

The talk will discuss the evolution of the low-k and ultralow-k dielectrics, the effects of the chemistries on the properties of the different types of the porous pSiCOH, and the behavior of such dielectrics during integration processing.

This work was performed by the Research Alliance Teams at various IBM Research and Development Facilities.