DYNAMIC IMAGES OF PLASMA PROCESSES - USE OF FOURIER BLOBS FOR END-POINT DETECTION DURING PLASMA-ETCHING OF PATTERNED WAFERS

By monitoring various process parameters (e.g., applied rf power, flow rate of gases, etc.) as a function of time, we show that Fourier seri es decomposition of the values of those parameters, at each time step, plotted on polar coordinates, gives closed curves representing the st ate of the plasma and the activity on the wafer. A change of the shape of the ''blob'' is a signature of the endpoint. The technique was suc cessfully applied on TiN/poly-Si, WSix, and doped poly-Si gate etch, a nd contact etch processes. Moreover, the method is reproducible from w afer to wafer and can be used easily by inexperienced operators to spo t endpoint in plasma processes. (C) 1998 American Vacuum Society.