Patent Document ID: 10102321
Application ID: 14537886
Patent Flag: 1

Claim One:
1. A method of defining a chuck model for a radio frequency (RF) transmission path to calculate a wafer direct current (DC) bias at a chuck of a plasma chamber, comprising: generating, by a computer, a cable model of an RF cable, a match model of an impedance matching circuit, a transmission model of an RF transmission line, and the chuck model, wherein the chuck model includes a series circuit model and a shunt circuit model, wherein the RF cable couples an RF generator to the impedance matching circuit and the RF transmission line couples the impedance matching circuit to the chuck; identifying an initial term in the chuck model having a first level of impact on a goodness of fit of the chuck model, wherein the initial term is identified from a plurality of initial terms; removing the initial term having the first level of impact on the goodness of fit from the chuck model, wherein the chuck model has a plurality of remaining ones of the plurality of initial terms after said removing of the initial term; identifying a non-initial term having a second level of impact on the goodness of fit of the chuck model with the non-initial term added to the chuck model, wherein the non-initial term is not one of the plurality of initial terms and is identified from a plurality of non-initial terms, wherein the second level of impact is greater than the first level of impact; selecting the remaining ones of the plurality of initial terms and the non-initial term having the second level of impact on the goodness of fit to update the chuck model; measuring a voltage and current to generate a measured voltage and current, wherein said measuring is performed by a voltage and current probe within the RF generator, wherein the voltage and current probe is coupled to an output of the RF generator; propagating the measured voltage and current via the cable model, the match model, and the transmission model to generate modeled voltage and current; calculating the wafer DC bias at a top surface of the chuck of the plasma chamber by propagating the modeled voltage and current via the remaining ones of the plurality of initial terms and the non-initial term in the chuck model; and controlling the plasma chamber based on the wafer DC bias to process a substrate placed within the plasma chamber.