Low-K CMP process control by using interpolation method
For ILD CMP process, accurate polish time control is required to obtain expected film thickness. Comparisons between conventional SiO2 CMP process and low-k CMP process were studied and realized polishing time for low-k material can not be determined by only removal rate due to the existence of incubation time at first stage. Interpolation method was evaluated to determine polishing time for low-k CMP process. Correction of this incubation time was performed by using interpolation method and promising results were obtained.
Polishing time calculation method to reduce oxide-film-CMP send-ahead works
In order to obtain higher throughput maintaining high precision in the CMP process, it is important to reduce send-ahead work and rework related to film thickness over the within-wafer distribution. This paper presents a new polishing time calculation method that ensures film thicknesses at all measurement positions satisfy the control limit, and gives a judgment on whether send-ahead work is necessary, with the margin of variation of film thicknesses from the control limits after CMP based on the within-wafer distribution of the removal rate and film thickness before CMP. The CMP-APC system applying these methods reduces the defects in film thickness after CMP, along with the amount of send-ahead work, which is half that of the former CMP-APC run-to-run control system.
Mathematical Simulation of Combustion of Boron Powder Gas Suspension
Based on a two-phase two-velocity model of a reacting gas-dispersed medium, a mathematical model of combustion of a boron powder gas suspension has been formulated. The results of numerical solution of the problem are presented. The influence of the composition of the gas suspension, its size, size distribution of particles, mass concentration of particles, as well as of the presence of aluminum powder in the suspension on the visible and normal velocities of flame propagation in the gas suspension, is shown. A comparison of the results of calculation with the well-known experimental and theoretical data is carried out. Satisfactory agreement of the predicted results with experimental data is shown.