Low-dielectric-constant materials (k < 3.0) have the advantage of facilitating manufacture of higher performance integrated-circuit (IC) devices with minimal increases in chip size. The reduced capacitance given by these materials permits shrinkage of spacing between metal lines to below 0.25 μm and the ability to decrease the number of levels of metal in a device. The technologies being considered for low-k applications are chemical vapor deposition (CVD) or spin-on of polymeric materials. For both types of processes, there are methods and materials capable of giving k < 3.0 dielectric stacks. This article will focus on the spin-on approach and discuss the properties of both organic and inorganic spin-on polymers.
While CVD SiO2 has been the mainstay of the industry, spin-on materials are appropriate for many dielectric applications. Polyimides have applications as electrical insulators, and traditional spin-on silicates or siloxanes (k > 3.0) have served as planarizing dielectrics during the last 15 years. The newer spin-on polymers have greatly enhanced mechanical, thermal, and chemical properties, exhibiting lower dielectric constants than the traditional materials.