Mark Daniel Bitner

Impact of Pore Size and Morphology of Porous Organosilicate Glasses on Integrated Circuit Manufacturing

Porous organosilicate materials produced by plasma enhanced chemical vapor deposition are the leading candidates for back-end-of-line dielectric insulators for IC manufacturing at 45nm design features and beyond. The properties of porous organosilicate glass films of dielectric constant k=2.50 ± 0.05 formed using diethoxymethylsilane and five different porogen precursors with an ultraviolet post treatment are reported. By varying the porogen precursor type pore sizes of 1-2 nm (equivalent spherical diameter) and porosities in the range of 24-31% were measured. While there were no observable trends in pore size with the molecular volume or plasma reactivity of the porogen precursor, modulus values ranged from 6.6 to 10.8 GPa. Porous films with the highest mechanical properties were found to have the highest matrix dielectric constant, highest network connectivity (lowest methyl content), and highest density. Within this process space, maximizing the network connectivity of the film was found to be more important to mechanical properties than lowering the total porosity. In effect, the choice of porogen precursor dictates the film morphology through its impact on the organosilicate glass matrix and pore size.

Plasma Enhanced Chemical Vapor Deposition of Porous Organosilicate Glass ILD Films With k ≤ 2.4.

We report on our work to develop a process for depositing nanoporous organosilicate (OSG) films via plasma enhanced chemical vapor deposition (PECVD). This approach entails codepositing an OSG material with a plasma polymerizable hydrocarbon, followed by thermal annealing of the material to remove the porogen, leaving an OSG matrix with nano-sized voids. The dielectric constant of the final film is controlled by varying the ratio of porogen precursor to OSG precursor in the delivery gas. Because of the need to maintain the mechanical strength of the final material, diethoxymethylsilane (DEMS) is utilized as the OSG precursor. Utilizing this route we are able to deposit films with a dielectric constant of 2.55 to 2.20 and hardness of 0.7 to 0.3 GPa, respectively.

Power coupling and utilization efficiencies of silicon-depositing plasmas in mixtures of H2, SiH4, Si2H6, and Si3H8

Adding Si2H6 or Si3H8 additives to SiH4/H2 discharges increases the growth rates for thin films of microcrystalline and amorphous silicon, but the reasons for this increase are not well understood. To better distinguish the chemical and physical from electrical effects of these additives, a comprehensive electrical study was performed for mixtures of H2, SiH4, Si2H6, and Si3H8. The power coupling efficiency, power utilization efficiency, voltage, current, impedance, and phase were measured as a function of total pressure, electrode gap, gas mixture, rf power, and time. The measurements identified a regime of pressure and gap in which the electrical behavior is optimized. In this regime, the power coupling efficiency is quite high and insensitive to gas mixture, and the power utilization efficiency also does not vary dramatically with mixture. Therefore, in this regime, chemical or physical effects of additives on growth rates predominate over electrical effects. Impedance models of the plasma and sheaths provide explanations for the optimized regime and its correlation with impedance phase. In addition, electrical signals were identified that can be used to detect a transient in the gas-phase density of silicon-containing molecules during deposition as well as other transient phenomena. The signals show promise for use in process monitoring and control.

Optimized Materials Properties for Organosilicate Glasses Produced by Plasma-Enhanced Chemical Vapor Deposition

In this paper we examine the relationship between precursor structure and material properties for films produced from several leading organosilicon precursors on a common processing platform. Results from our study indicate that for the precursors tested the nature of the precursor has little effect upon film composition but significant impact on film structure and properties. Introduction There are a variety of materials being considered for the next generation interlayer dielectric (ILD) materials. The leading candidates for the 90nm generation are organosilicate glasses produced by Plasma-Enhanced Chemical Vapor Deposition (PECVD). Providing materials with extendibility beyond a single generation solution requires the optimization of both electrical and mechanical properties. These are competing goals since concomitant with reducing the dielectric constant (k) is, in general, a decrease in the mechanical strength of a material. The goal of this work is to build a better understanding of the structure of low k dielectric films deposited from a PECVD process. In attempts to elucidate structureproperty relationships for OSG precursors we assessed a variety of chemicals including those used in various commercial product offerings. Experimental All experiments were performed on an Applied Materials Precision 5000 fitted with a 200mm DxZ chamber. Every attempt was made to optimize process regimes for each precursor to provide the best mechanical properties at a given dielectric constant (k). Films were analyzed for refractive index and thickness with a SCI FilmTek 2000 reflectometer calibrated daily. Electrical tests were performed on low resistivity wafers ( 20 ohm-cm) using a Thermo Nicolet 750 at 4 cm resolution, nitrogen purged cell and background corrected with Si. Selected samples were analyzed using Carbon-13 and Silicon-29 Nuclear Magnetic Resonance (NMR). Density Molecule Si–CH3:Si Si–O:Si Si–H:Si Structure