| Budget Amount *help |
¥15,100,000 (Direct Cost: ¥15,100,000)
Fiscal Year 2006: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥11,600,000 (Direct Cost: ¥11,600,000)
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| Research Abstract |
Chlorine-and Bromine-containing plasmas are now indispensable for the etching of silicon, metals, and metal oxides (high dielectric constant / high-k materials) in the fabrication of sub-0.1 μm devices. We have developed an atomic-scale model of the particle transport and surface reactions, to simulate the feature profile evolution for nanometer-scale control of the profile and critical dimensions during etching in chlorine-and bromine-containing plasmas. In the model, the substrates are taken to consist of a large number of small (or atomic-scale) cells or lattices, and the evolving interfaces are modeled by using the cell removal method. The model takes into account the transport of ions and neutrals in microstructures, along with surface reactions of ion-enhanced etching, chemical etching, surface reflection and penetration of ions, surface reemission of neutrals, surface oxidation, deposition of etch products and by-products, and removal of oxidized and deposited surfaces by sputte
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ring. The trajectory of ions on feature surfaces and in substrates is analyzed by the Monte Carlo calculation, based on the momentum and energy conservation for an incident ion through successive two-body elastic collisions with substrate atoms. The interaction potential is calculated using the quantum chemical scheme "Gaussian" for the Cl-Si and Br-Si system. The numerical results indicated that for the nanometer-scale control of etched profiles relies largely on a competitive formation of surface passivation layers through deposition of etch products/by-products and surface oxidation, and on a competition between the ion reflection and passivation layer formation on feature surfaces during etching.
Moreover, we have developed in situ diagnostics of reactants and reaction products in the gas phase and on substrate surfaces during plasma etching, including laser-induced fluorescence (LIF), Fourier transform infrared (FTIR) absorption spectroscopy, and quadruple mass spectrometry (QMS), in addition to optical emission spectroscopy (OES) and Lagmuir probe measurement. We then investigated the etching of high-k gate materials Si, HfO_2, Pt and TaN in chlorine and bromine-containing plasmas, to gain a better understanding of the etching mechanisms concerned. Based on the numerical analysis and diagnostics, we found a highly selective etching process for HfO_2 over Si, without rf biasing or under low ion energy conditions. The numerical and experimental results implied that a competition between the etching and deposition on surfaces, together with a competition between the formation and quenching of surface inhibitors in the gas phase, is responsible for the phenomena observed. Less
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