Processing and Characterization of Silica Xerogel Films for Low-K Dielectric Applications

Abstract

Surface modified silica xerogel films of high porosity (60 - 90 %) and uniform thickness (0.4–2 μm) were fabricated at ambient pressure on silicon and silicon dioxide. The rheological properties that govern film uniformity were determined. A relation between the final dried film thickness and spin speed was developed. The porosity and thickness of the films could be controlled independently. The same porosity could be obtained over a wide range of aging time and temperature combinations. Fracture toughness was measured using the edge-lift-off technique. The best values were comparable to concrete. Surface modification was affected by treating the film with trimethylcholorosilane (TMCS) and other modifiers. Moisture adsorption was studied at 100% RH using a quartz crystal microbalance technique. Depending upon the degree and kind of surface treatment, films absorbed as much as 32% or as little as 2% of their weight in water. Dielectric constants (K), losses and breakdown strengths were comparable to values for calcined, bulk aerogels. Thin (≤ 500 Å) films of Copper (Cu) and Tantalum (Ta) were deposited on xerogel films and subjected to thermal annealing. No diffusion was observed within the limits of RBS. High-density plasma etching showed that the films etch an order of magnitude faster than conventional SiO2 films.

Sol–gel derived mesoporous silica films using amphiphilic triblock copolymers

“…Mesoporous silica (SiO 2 ) films with high porosities, well-ordered and controlled pore sizes are potentially useful as an interlayer dielectric material for advanced semiconductor devices that require a low dielectric constant [12,14,[16][17][18][19]. It is generally accepted that dielectric constants of mesoporous silica films are considerably dependent on the porosity and pore surface state of the films [14,17].…”

“…It is generally accepted that dielectric constants of mesoporous silica films are considerably dependent on the porosity and pore surface state of the films [14,17]. The specific mechanism for the formation of mesostructures is the current subject of discussions, but different mesostructures can be obtained by varying the synthetic conditions.…”

Etching of xerogel in high-density fluorocarbon plasmas

“…11. 2 Operating at similar conditions for CHF 3 but with significantly more capacitive coupling, it was found that the normalized etch rates of 58% and 69% xerogel films are higher than the SiO 2 etch rates as opposed to the results shown in Fig. 4.…”

“…However, the porosity may also introduce problems, such as low mechanical strength and moisture absorption. 2 In this work we have studied three different xerogels for which all these problems have been minimized. Some of the properties are outlined in Table I.…”

Processing and characterization of ultralow-dielectric constant organosilicate

“…Compared to the mean free path of air, ϳ60 nm, 19 the shapes and structures of these pores, whether they are closed or interconnected, will have no effect on the dielectric properties of porous MSQs. This may be due to the extremely small mean free path of these pores.…”