Patent ID: 7470626

Claim:
A method of operating a plasma reactor chamber with respect to two plasma parameters selected from the group consisting of ion density, wafer voltage, etch rate, wafer current, by controlling chamber parameters of source power, bias power and chamber pressure, said method comprising: characterizing the reactor chamber by performing the steps of: a. for each one of said selected chamber parameters, ramping the level of the one chamber parameter while sampling RF electrical parameters at an RE bias power input to a wafer support pedestal and computing from each sample of said RF electrical parameters the values of the plasma parameters, and storing said values with the corresponding levels of said one chamber parameter as corresponding chamber parameter data; b. for each one of said selected chamber parameters, deducing, from the corresponding chamber parameter data, a single variable function for each of said plural plasma parameters having said one chamber parameter as an independent variable; c. constructing combinations of said functions and from said combinations, constructing surfaces defining simultaneous values of all of said selected chamber parameters, each respective surface corresponding to a respective constant value of one of said plural plasma parameters, and storing said surfaces; controlling a plasma in the chamber during processing of a production wafer in the chamber in accordance with user-selected values of each of said plural plasma parameters by performing the following steps: a. for each one of said selected plasma parameters, fetching a relevant surface of constant value corresponding to the user-selected value of said one plasma parameter, and determining an intersection of the relevant surfaces, said intersection corresponding to a target value of source power, bias power and chamber pressure; and b. setting said source power, bias power and the pressure in said chamber, respectively, to the respective target value.