US 7,247,218 B2Granted

Plasma density, energy and etch rate measurements at bias power input and real time feedback control of plasma source and bias power

AssigneeApplied Materials, Inc.

InventorDaniel J. Hoffman

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Abstract

A plasma reactor process measurement instrument includes an input phase processor receiving wafer bias voltage, current and power and computing an input impedance, an input current and an input voltage to the transmission line; a transmission line processor for computing a junction admittance of a junction between the transmission line and the conductive grid from the input impedance, input current and input voltage and from parameters of the transmission line; a grid-to-ground transformation unit for providing shunt electrical quantities of a shunt capacitance between the grid and a ground plane; a grid-to-wafer transformation unit for providing load electrical quantities of a load capacitance between the grid and the wafer; and, a combined transformation processor for computing the at least one of the etch rate, plasma ion density and wafer voltage from the junction admittance, the shunt electrical quantities, the load electrical quantities and a frequency of the RF power generator.

Claims26

Dependent claims

A plasma reactor having an instrument for measuring at least one of:

(a) etch rate, (b) plasma ion density, (c) wafer voltage, during processing of a semiconductor wafer on a workpiece support within a chamber of the plasma reactor containing a plasma, said reactor including an RF power generator coupled from an impedance match circuit through a transmission line to a conductive grid within the workpiece support, said impedance match circuit including sensing circuitry, said instrument comprising:
an input phase processor connected to said sensing circuitry and configured to compute from outputs of said sensing circuitry an input impedance, an input current and an input voltage to said transmission line;
a transmission line processor configured to compute a junction admittance of a junction between said transmission line and said conductive grid from said input impedance, input current and input voltage and from parameters of said transmission line;
a grid-to-ground transformation unit configured to provide shunt electrical quantities of a shunt capacitance between said grid and a ground plane;
a grid-to-wafer transformation unit configured to provide load electrical quantities of a load capacitance between said grid and said wafer;
and
a combined transformation processor configured to compute the at least one of said etch rate, plasma ion density and wafer voltage from all of the following:
said junction admittance, said shunt electrical quantities, said load electrical quantities and a frequency of said RF power generator.

5 more elements

A plasma reactor comprising:

a vacuum chamber and a wafer support pedestal within said chamber for supporting a wafer to be processed within said chamber;
a process gas inlet for furnishing process gases into said chamber;
an RF source power applicator, and a plasma RF source power supply coupled to said RF source power applicator;
a plasma RF bias power supply coupled through an RF power path to said wafer support pedestal;
a memory storing sets of contours of constant performance parameter values for one of bias power and source power as a function of the other, said sets of contours comprising at least two of a set of contours of constant wafer voltage, a set of contours of constant ion density, and a set of contours of constant etch rate;
a process set point controller configured to accept user-defined target values for control parameters comprising at least two of wafer voltage, ion density and etch rate corresponding to the set of contours stored in said memory and configured to find a pair of source power and bias power values at which the corresponding ones of said contours of constant performance parameter values intersect;
and
said process set point controller having an output at which said pair of source power and bias power values are coupled as power level commands to said plasma RF source power supply and said plasma RF bias power supply, respectively.

5 more elements

Dependencies are inferred from the claim text.