Determination of the Modulus and Hardness of Spin-on Zeolite Low-K Thin Films
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Determination of the Modulus and Hardness of Spin-on Zeolite Low-K Thin Films Mark Johnson1, Zijian Li 2, Yushan Yan2 and Junlan Wang1 1
Department of Mechanical Engineering, Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521 2
Abstract With the semiconductor technologies continuously pushing the miniaturization limits, there is a growing interest in developing novel low dielectric constant (low-k) materials to replace traditional dense SiO2 based insulators. In order to survive the multi-step integration process and provide reliable material and structure for the desired integrated circuit (IC) functions, the new low-k materials have to be mechanically strong and stable. Thus the material selection and mechanical characterization are vital in the successful development of next generation low-k dielectrics. A new class of low-k dielectric materials, nanoporous pure-silica zeolite, is prepared in thin films using IC compatible spin coating process and characterized using depth sensing nanoindentation technique. The elastic modulus measurements of the zeolite thin films are found to be significantly higher than that of other porous silicates with similar porosity and dielectric constants. Correlations of the mechanical, microstructural and electrical properties are discussed in detail. Introduction As the size of semiconductors continually decrease, problems such as crosstalk, power dissipation and RC delay greater influence the performance of integrated circuits (IC). This has generated much concern because although the traditional dense silicon dioxide (SiO2) based insulators are mechanically stable, their application in microelectronic devices is limited by their dielectric constant (k ≈ 4.0). One solution is to lower the dielectric constant of SiO2 through the introduction of porosity. However, this compromises the mechanical properties of the structure. The mechanical properties are significant since low-k materials have to withstand significant stresses developed during the packaging process and also have to survive the chemical mechanical polishing (CMP) during chip processing. Strong mechanical properties of the low-k material are extremely vital to ensure that the material will function properly throughout the lifetime of an integrated circuit. Nanostructured zeolite films have been synthesized and demonstrated to be a promising lowk material [1]. Zeolites are microporous crystalline solids with a molecular framework consisting of oxygen, silicon and/or aluminum. The strong crystalline framework structure and small uniform pores (0.3 to 2 nanometers [2]) of zeolites make them promising candidates for use in low-k applications. While the high porosity of zeolite thin films significantly reduces the k values, strong crystalline framework maintains a comparatively higher mechanical strength than other amorphous porous silicas. In this paper, nanoindentation technique is used to characterize elastic modulus and hardness of pure silica zeolite (PSZ) MEL l
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