In situ and real time control of the different process steps in semiconductor device manufacturing becomes a critical challenge, especially for the lithography and plasma etching processes. Dynamic scatterometry is among the few solutions able to meet the requirement for in line monitoring. In this article, the authors demonstrate that dynamic scatterometry can be used as a real time monitoring technique during the resist trimming process. Different process parameters, such as chemistries and bias power, were used in the experiments for the demonstration; they discuss the influence of these different parameters on the measurement. For validation purposes, the dynamic scatterometry measurements are compared to three dimensional atomic force microscopy measurements made in the same process conditions. The agreement between both is excellent.