High strength, low dielectric constant fluorinated silica xerogel films

Abstract

The mechanical, electrical, and microstructural properties of low-k fluorinated silica xerogels produced using a one step spin-on process are reported. Derived from a fluorinated silane monomer, these films are easily processed and exhibit very low dielectric constants (2.1 as processed and 2.3 after heat treating at 450 °C in air). Structural determination by Fourier transform infrared spectrophotometry indicates a fluorinated silica structure with shortened Si–O bonds; however, some of the fluorine is lost during annealing. Nanoindentation studies show high elastic moduli (12 GPa) and hardness (1 GPa). Microstructural analyses by transmission and scanning electron microscopy indicate an unusual morphology with highly linked features and pore sizes in the 20–30 nm range. We believe the low dielectric constants and robust mechanical properties are due to the unusual microstructure of these films.

Reinforcement mechanism for mechanically enhanced xerogel films

“…Modulus and hardness both increase as inverse functions of porosity, but show a very rapid increase over a very small increase in porosity [12]. Previous work has shown that the dielectric constant for these materials is 2.3 [13].…”

“…Our recent work indicates that xerogel compositions with chemistries that yield lower dielectric constant materials can exhibit enhanced elastic modulus and hardness [13,14]. Lin et al report that elastic moduli of 5 GPa are necessary to endure chemical-mechanical planarization (CMP) although some modifications such as a hard mask permit materials with moduli of approximately 3 GPa to survive integration [15].…”

Structural characteristic and thermal stability of nanoporous SiO2 low-k thin films prepared by sol–gel method with catalyst HF

“…Wang). sition (PECVD) of silica with a fluorine source, such as CF 4 and SiF 4 gases, or PECVD of triethoxy-fluorosilane gas [6]. On the other hand, even with the incorporation of fluorine ions, the current leading approaches to achieve ILD films with the k value of around 2.0 are only to make them porous [7].…”

Plasma damage mechanisms for low-k porous SiOCH films due to radiation, radicals, and ions in the plasma etching process

“…Many researchers have investigated various kinds of organic, inorganic, and hybrid materials as alternatives to the conventional interlayer dielectric film of SiO 2 ͑k = 4.0͒. [1][2][3][4][5][6] Furthermore, porous materials have been intensively investigated as ultralow k materials for next generation ULSIs. 7 Many serious problems occur when low-k films are used as insulating materials for ULSIs.…”