Laser Trimming Modeling of Thin Film Integrated Resistors

A new method for laser trimming modeling of integrated thin film resistors is presented. The method, based on the conformal mapping of the distributed domain which corresponds to the resistor under trimming, relies on the analytical results obtained in the study of Laplace fields with the aid of complex functions. As we already got good results in other applications, we will show that the method is also very convenient to be used in present modeling too, because it provides a rapid and precise answer for the two main problems of trimming: (i) evolution of the resistance value during the trimming process and (ii) current flow in the resistive film after trimming. Laser trimming of a thin film resistor having a 'top hat' shape is presented in order to exemplify the advantages of the proposed method.