System, method, and apparatus for controlling ion energy distribution in plasma processing systems
Systems, methods and apparatus for regulating ion energies in a plasma chamber and chucking a substrate to a substrate support are disclosed. An exemplary method includes placing a substrate in a plasma chamber, forming a plasma in the plasma chamber, controllably switching power to the substrate so as to apply a periodic voltage function (or a modified periodic voltage function) to the substrate, and modulating, over multiple cycles of the periodic voltage function, the periodic voltage function responsive to a defined distribution of energies of ions at the surface of the substrate so as to effectuate the defined distribution of ion energies on a time-averaged basis.
1. A method for creating a voltage waveform at an output of a bias supply, the method comprising:
maintaining a negative voltage coupled to the output through an inductor;
connecting a first voltage to the output and then disconnecting the first voltage from the output to produce a first portion of the voltage waveform at the output that increases to a second portion of the voltage waveform;
connecting, after the first voltage is disconnected from the output, a second voltage to the output and then disconnecting the second voltage from the output to produce a third portion of the voltage waveform that decreases from the second portion of the voltage waveform; and
wherein the negative voltage remains connected to the output through the inductor and wherein a fourth portion of the voltage waveform is produced that decreases in a ramp-like manner from the third portion of the voltage waveform while the first voltage and the second voltage are disconnected from the output.
2. The method of claim 1 , wherein connecting the first voltage to the output includes connecting the first voltage to the output through an inductive element.
3. The method of claim 1 , wherein connecting the second voltage to the output includes connecting the second voltage to the output through an inductive element.
4. The method of claim 1 wherein connecting the second voltage to the output includes connecting ground to the output.
5. An apparatus for creating a voltage waveform comprising:
means for maintaining a negative voltage connected to the output through an inductor;
means for connecting a first voltage to the output and then disconnecting the first voltage from the output to produce a first portion of the voltage waveform at the output that increases to a second portion of the voltage waveform;
means for connecting, after the first voltage is disconnected from the output, a second voltage to the output and then disconnecting the second voltage from the output to produce a third portion of the voltage waveform that decreases from the second portion of the voltage waveform; and
wherein the means for maintaining the negative voltage connected to the output includes means for maintaining the negative voltage connected to the output through the inductor while both, the first voltage and the second voltage are disconnected from the output to produce a fourth portion of the voltage waveform that decreases in a ramp-like manner from the third portion of the voltage waveform.
6. The apparatus of claim 5 , wherein the means for connecting the first voltage to the output includes means for connecting the first voltage to the output through an inductive element.
7. The apparatus of claim 5 , wherein the means for connecting the second voltage to the output includes means for connecting the second voltage to the output through an inductive element.
8. The apparatus of claim 5 , wherein the means for connecting the second voltage to the output includes means for connecting ground to the output.
9. An apparatus for creating a voltage waveform, the apparatus comprising:
at least one DC voltage source to provide a first voltage and a second voltage;
a negative DC voltage source configured to apply a negative voltage to an output through an inductor;
a first switch disposed to switchably connect the first voltage to the output;
a second switch disposed to switchably couple the second voltage to the output;
means for closing the first switch to increase, along a first portion of the voltage waveform, a level of the voltage waveform at the output to a second portion of the waveform, and then opening the first switch; and
means for closing, after the first switch is opened, the second switch to decrease, along a third portion of the waveform, the level of the voltage waveform at the output to a second voltage level, and then opening the second switch; and
wherein the DC voltage source remains coupled to the output and produces a fourth portion of the voltage waveform that decreases in a ramp-like manner from the third portion of the voltage waveform while the first switch and the second switch are open.
10. The apparatus of claim 9 , wherein the first switch is disposed to connect the first voltage to the output through an inductive element.
11. The apparatus of claim 9 , wherein the second switch is disposed to connect the second voltage to the output through an inductive element.
12. The apparatus of claim 11 wherein the second switch is disposed to connect ground to the output.