We have developed a simulation for predicting reactive ion etching (RIE) topography, which is a combination of plasma simulation, the gas reaction model, the sheath model and the surface reaction model. The simulation is applied to the SiO 2 etching process of a high-aspect-ratio contact hole using C 5 F 8 gas. A capacitively coupled plasma (CCP) reactor of an 8-in. wafer was used in the etching experiments. The baseline conditions are RF power of 1500 W and gas pressure of 4.0 Pa in a gas mixture of Ar, O 2 and C 5 F 8 . The plasma simulation reproduces the tendency that CF 2 radical density increases rapidly and the electron density decreases gradually with increasing gas flow rate of C 5 F 8 . In the RIE topography simulation, the etching profiles such as bowing and taper shape at the bottom are reproduced in deep holes with aspect ratios greater than 19. Moreover, the etching profile, the dependence of the etch depth on the etching time, and the bottom diameter can be predicted by this simulation.

The CF4 and C4F8 gas etching profiles of oxide films were compared by multiscale simulation that comprises gas reaction, sheath, and surface reaction models. The densities of CF3, CF2, and CF radicals in CF4/Ar or C4F8/Ar gas were measured and compared with those obtained by simulation using the gas reaction model. From this comparison, the electron temperatures were determined to be 2.8 and 4.5 eV for CF4 and C4F8 gases, respectively. In the sheath model, the behavior of ions in a sheath was simulated for sheath lengths calculated from these electron temperatures. In the surface reaction model, we simulated the formation of a polymer and active layers by CF2 radicals, determined the depth of etching resulting from ion bombardment, and obtained the etching profiles of the oxide films. The profile of a contact hole with a depth of 820 nm and an aperture diameter of 160 nm was simulated. The results showed that the photoresist height was approximately 70 nm greater and the bowing diameter was approximately 10 nm smaller in the case of using C4F8 gas than in the case of using CF4 gas. This is because the CF2 density in the C4F8 gas is approximately 30 times higher than that in the CF4 gas and the polymer layer more strongly protects the underlying film. When the etching profiles were simulated with a fixed density of positive ions but with various CF2 density, the bottom diameter was constant but the bowing diameter changed for CF2 densities between 1013 and 1014 cm−3.

Articles you may be interested inInfinitely high etch selectivity during CH 2 F 2 / H 2 dual-frequency capacitively coupled plasma etching of silicon nitride to chemical vapor-deposited a -C J. Vac. Sci. Technol. A 28, 755 (2010); 10.1116/1.3430551 TiSiN films produced by chemical vapor deposition as diffusion barriers for Cu metallization Microscopic mapping of specific contact resistances and long-term reliability tests on 4H-silicon carbide using sputtered titanium tungsten contacts for high temperature device applications With the shrinking design rule of semiconductor devices, the aspect ratios of contact holes that connect transistor electrodes to wirings have exceeded 10 at a design rule less than 0.15 m. The contact is formed through sequential processes of reactive ion etching ͑RIE͒, TiN sputtering, and tungsten chemical vapor deposition ͑W-CVD͒. In such a formation process, a contact hole with a large bottom diameter is required to reduce contact resistance. We developed a contact simulation method for optimizing contact formation. This contact simulation involves sequential simulations of RIE, TiN sputtering, and W-CVD processes, which adopt a particle model based on the Monte Carlo method. These topography simulations were calibrated using experimental results, and each simulation was combined in order to calculate these sequential simulations. We calculated the dependences of etching and W-CVD filling profiles on contact hole depth. The simulation profiles of etching and W-CVD filling were in agreement with the experimental results. The sequential simulations showed that W disconnection occurs at over 2.5 m contact depth with a aspect ratio of 19.2 and the contact resistance increases markedly.

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Using a semiclassical approach, we have calculated electron-, proton-and ionized helium-impact line widths and shifts for 22 A11 multiplets. The resulting data have been compared with existing experimental and theoretical values. Physica Scripta 49