Browsing by Author "Chien S.-W"

This article proposes a numerical model to predict the abatement process of carbon tetrafluoride (CF4) in a reaction chamber with the assistance of nitrogen thermal plasma generated by a nontransferred and direct-current torch. The magneto-hydrodynamic equations, that is, the continuity, momentum, energy, and current continuity equations together with turbulence transport equations, are solved by an in-house parallelized finite volume code to obtain the thermal plasma flow jetting out the plasma torch. The thermal plasma is assumed in local thermal equilibrium, optically thin and electrically neutral. In the reaction chamber, a kinetics model is adopted to describe the transport phenomena as well as the chemical interactions among various species involving in the decomposition process. Fifty-six species and 235 chemical reactions are considered in the proposed full kinetic model. Three different models, namely a full kinetic one, a reduced one, and a simplified one, are compared for the prediction accuracy of the destruction and removal efficiency (DRE) along with the abatement products formed in the decomposition process. With the full kinetic model, the predicted DRE at three CF4 concentration conditions, that is, 7200, 12 600, and 16 000 ppm, has a good agreement with the experimental result indicating a nearly full decomposition except for a very small discrepancy less than 0.5% for the case of 16 000 ppm. The predicted abatement efficiency becomes saturated and approaches to a complete abatement provided the participated H2 O outnumbers CF4 in moles. A dry abatement process is forecast with a destruction rate decline from 97% to 92% as the CF4 concentration grows from 7200 to 16 000 ppm. Although the reduced kinetic model along the simplified model using a compact set of chemical reactions underpredicts the DRE for the investigated CF4 concentration in the range of 1%-2%, they practically deliver an incomplete group of abatement products that might mislead a proper design of the scrubber behind the reaction chamber. The validation with the experimental measurement justifies the employment of the proposed full kinetic model capable of delivering an accurate abatement prediction of the detoxifying process of CF4. ? 1973-2012 IEEE.

In subwavelength lithography, printed patterns on the silicon wafer suffer from geometric distortions and differ from the original design. These nonrectangular patterns can seriously affect electrical characteristics and circuit performances. We extend the verification of location-dependent weighting method and further propose three single equivalent gate length (EGL) extraction methods for representing each nonrectangular gate (NRG) transistor with a single EGL model. These methods are applied to sub-20-nm fully depleted silicon on insulator (FDSOI) circuits to predict the postlithography performances. An in-house extreme ultraviolet lithography simulation tool is utilized for nonrectangular pattern simulation. Shape information is imported to TCAD to construct three-dimensional nonrectangular FDSOI transistor models. The accuracy of the location-dependent weighting method and EGL extraction methods is verified with TCAD circuit simulations. Preliminary simulation results indicate that weighting factors can improve the accuracy of electrical characteristics estimation, especially in leakage current analysis. On average, the EGLs extracted from off-state only data, and from data lumping both off- and on-states, respectively, can each predict SRAM electrical characteristics with overall error <1 %, or a factor of 5 accuracy improvement over the EGLs extracted without the weightings. These methods could be used to simulate large-scale sub-20-nm FDSOI circuits with NRG transistors caused by nonideal optical effects. ? 2021 Society of Photo-Optical Instrumentation Engineers (SPIE).

Our work presents and investigates the effectiveness of a model-based proximity effect correction method for helium ion beam lithography (HIBL). This method iteratively modulates the shape of a pattern by a feedback compensation mechanism until the simulated patterning fidelity satisfies specific constraints. A point spread function (PSF) is utilized to account for all phenomena involved during the scattering events of incident ion beam particles in the resist. Patterning prediction for subsequent correction process is derived from the energy intensity distribution due to convolution between the PSF and the pattern, with an adequate cut-off threshold. The performance of this method for HIBL is examined through several designed layouts from 15- to 5-nm in half pitches, under specific process parameters, including acceleration voltage, resist thickness, and resist sensitivity. Preliminary results show its effectiveness in improving the patterning fidelity of HIBL. ? 2021 Society of Photo-Optical Instrumentation Engineers (SPIE).