For faster, smaller, and higher performance integrated circuits, a low dielectric constant insulator is required to replace silicon dioxide. Here the properties of a new dielectric—SiLK resin, a solution of a low‐molecular‐weight aromatic thermosetting polymer—are reviewed and examples of its application in the fabrication of interconnect structures, such as the one shown in the Figure, are given.
Adherence to the prescript of Moore's law continues to drive materials development for new and lower dielectric constant materials for use as back-end-of-line (BEOL) interlayer dielectric in advanced logic IC's. As is the case for the current generation of low-K materials (<3.0), these ultra-low K materials (<2.2) will need to meet the variety of integration and reliability requirements for successful product development. Excluding the incorporation of fluorine to lower the material polarity, further reductions of dielectric constant can only be achieved by reduced density. Based upon the industry's experience with the current class of full density dielectrics, process integration may be challenging for ultra-low K materials. This anticipated difficulty derives from the profound differences in material properties, e.g. mechanical integrity, as one lowers the material density, which in turn confounds existing manufacturing processes that have evolved over 35 years based on silicon dioxide.Minimizing these material and processing differences by extending leveraged learning from previous technology nodes is essential for timely and cost-efficient development cycles. As a result, material selection of a full density low-K is somewhat influenced by the ability of that material to be extended into future generations. Understanding how the material properties will change as its density is lowered is vital to this selection process. In this paper, we present a summary of models for calculating effective properties as a function of density and apply these to current low-K materials with emphasis on mechanical integrity. We will also review experimental methods for measuring the mechanical integrity of ultra-low K materials and compare the results to the various models described herein.
Three low dielectric constant organic polymers are being investigated for possible use in a conventional, subtractive etch, multi-level metal process with PVD Al plugs. Material properties, physical properties, planarization ability and etch chemistries are compared, as well as the possibility of using these materials in a low temperature PVD A1 plug process.
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