Research progress on porous low dielectric constant materials

With the rapid development of ultra-large-scale integration (ULSI) of integrated circuits, the feature size of the silicon chip continues shrinking and the physical gate length is approaching to 15 nm. At the same time, the wring density increases dramatically. The problems of the resistance-capacity (RC) delay, crosstalk noise, and power dissipation caused by the metal resistance and parasitic capacitance between lines and layers, become more and more prominent. Therefore, urgent requirements have been put forward for low-dielectric constant (low-k) materials with improved dielectric properties for insulation between the metal lines and layers. Remarkably, using low-permittivity air gaps to replace part of the densely arranged solid dielectric layer has become one of the important ways to develop ultra-low-k materials. Herein, from the perspective of the porous materials’ compositions, this review summarizes the synthesis and characterization of porous low-k materials, and the structure-property relationship reported in the past two decades, including inorganic, organic, and organic-inorganic hybrid porous materials. Besides, the advantages and disadvantages of various types of porous materials in preparation methods and low-k applications are compared, and the possible future development directions and potential application prospects are also proposed.