Roland Rzehak

Greenwood–Williamson Model Combining Pattern-Density and Pattern-Size Effects in CMP

Chemical mechanical planarization (CMP) models which are able to make predictions for a full chip are highly desirable in semiconductor manufacturing. Previous models proposed to this end have largely focused on effects of pattern density. We here extend one of the proposals to include also effects of pattern-size based on a consideration of the roughness of the polishing pad. Experimental data from CMP test structures containing variations of both pattern-density and pattern-size are used to validate the model. The results are applied to both interlayer dielectric-CMP and shallow trench isolation-CMP as particularly important processes in industry.

CFD for Subcooled Flow Boiling: Parametric Variations

We investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler/Euler two-phase flow description with heat flux partitioning. Very similar modeling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant nondimensional numbers have been realized in the DEBORA tests using dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, liquid temperature, and bubble size. Robust predictive capabilities of the modeling require that it is validated for a wide range of parameters. It is known that a careful calibration of correlations used in the wall boiling model is necessary to obtain agreement with the measured data. We here consider tests under a variety of conditions concerning liquid subcooling, flow rate, and heat flux. It is investigated to which extent a set of calibrated model parameters suffices to cover at least a certain parameter range.

CFD for Subcooled Flow Boiling: Analysis of DEBORA Tests:

In this work we investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler/Euler two-phase flow description with heat flux partitioning. Very similar modelling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using Dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size.Robust predictive capabilities of the modelling require that it is validated for a wide range of parameters. In previous studies (Krepper and Rzehak, 2011, 2013) it was shown that a careful calibration of correlations used in the wall boiling model is necessary to obtain agreement with the measured data. We here consider tests under a variety of conditions concerning liquid subcooling, flow rate and heat flux. I...

CFD Simulation of Flashing Boiling Flow in the Containment Cooling Condensers (CCC) System of KERENA™ Reactor

The flashing boiling phenomenon occurring inside the Containment Cooling Condensers (CCC) passive system of KERENA™ reactor was simulated by using the CFD (Computational Fluid Dynamics) code ANSYS CFX. The steam generation was assumed to be caused by thermal phase change, which is controlled by interphase heat transfer. In general, the model setup is able to capture the generation and disappearance of steam and the fluctuation of pressure and temperature observed during the flashing. However, since the nucleation and bubble growth process was neglected in the simulation, the initialization of evaporation was found to be a key issue, which depends on the prescribed bubble size sensitively. In order to get a satisfying agreement with the experimental data, a relatively large size has to be assumed for the selected test case (db>10 mm). The CFD results are qualitatively comparable to those obtained by using the system code ATHLET, except that the mass transfer rate is higher and the fluctuation frequency and altitude is lower. In addition, the assumption of constant bubble size might introduce significant error. The change of bubble size as well as the effect of nucleation and bubble growth should be investigated in the future work. For this purpose, however, further experimental data such as evaporation rate, phase and bubble size distribution, phase velocity are required.Copyright

Pad roughness effects on the planarization and material removal rate in CMP processes

Chemical-mechanical planarization (CMP) is one of the most demanding process steps in interconnect integration. Therefore we systematically investigate the planarization of adjacent line-space structures, which emulate IC layouts, as a function of the conditioning process. The interrelation between conditioning, pad roughness and planarization is evaluated by a novel pad roughness characterization methodology. Using this approach, tribological parameters can be correlated to important CMP properties like global step reduction and blanket removal rate, enabling planarization improvements for patterned dielectrics and metals.