MONTE CARLO SIMULATION AS PROCESS CONTROL AID

Field emission from carbon nanotubes (CNT) for display purposes was optimized using Design of Experiments (DOE). The brightness was improved by three orders of magnitude but the achieved gains could not be sustained in the “Control” phase of a DMAIC project and the process reverted to poor performance. It took an intense effort of circa two months to recover the process. Monte Carlo simulations were used to provide an excellent fit to all the measured emission data over the course of eight months in both range and shape. The simulations were also indicating the cause of the process drift. A hidden factor that was too time- and labor-intensive to measure in real-time was responsible and uncovered. With the aid of the simulations the process could have been recovered within days instead of months.