The Research Of The Structure And Electrical Property Of The Porous Low K SiO₂: F Film

The interlayer dielectric materials with ultra low dielectric constant are researched to adapt to the development of the high speed and high density for ultra large scale integrated circuit (ULSI).In this paper, the porous silica films catalyzed by HF and HC1 are prepared by sol-gel process with non-ionic surfactant-template PPE. The pattern, structure and electrical property based on SCLC method of the films are discussed to seek for the relations of the film structure and the electrical property.The result of the test shows that films catalyzed with HF have good properties, the dielectric constant is about 1.524. Modification, annealing, and the surfactant can optimize the property of the film. The analysis of the pattern and electrical property of the films with different layers are emphasized in this paper. A model of cascade and overlay was established to explain the coacervation of the colloidal granules. The I-V characteristic and the density of the states of the silica films with different dose of F are analyzed. The result of the test shows that the small quantity addition of the HF can optimize the property of the film, but more addition of the HF can make the property of the film worse, which is due to the etching process of the HF on the silica skeleton. F element existed in HF substitutes easily the -OH to form stable Si-F, and it also breaks easily the Si⁰ bond to create more Si-OH, which creates SiF₄ gas in the end. The origin of the trap states is the dangling bond lied on the wall of hole. Porous materials have specific shape of the I-V curve. The trap states lied on the wall of hole (dangling bond) are also the origin of the specific shape of the I-V curve. Uv-Vis test and temperature-change I-V test on F doped silica film, shows that there are intrinsic adsorption and exciton adsorption existed in the film. The energy band structure diagrammatic sketch of the low k material in MOS structure was obtained.There are two pairs of competitive factors in the F doped porous low k silicamaterials: porous and mechanical strength, porous and electrical property. The doped porous can decrease dielectric constant, but make the mechanical strength and electrical property get worse.