System, method and apparatus for controlling ion energy distribution of a projected plasma
View Patent ↗Systems, methods and apparatus for regulating ion energies in a plasma chamber are disclosed. An exemplary method includes placing a substrate in a plasma chamber, forming a plasma in the plasma chamber via a remotely generated ionizing electromagnetic field that extends into the plasma chamber from a remote projected source, controllably switching power to the substrate so as to apply a periodic voltage function to the substrate, and modulating, over multiple cycles of the periodic voltage function, the periodic voltage function responsive to a desired distribution of energies of ions at the surface of the substrate so as to effectuate the desired distribution of ion energies on a time-averaged basis.
1. A system for plasma-based processing, comprising:
a field generation portion that generates an ionizing electromagnetic field, wherein the ionizing electromagnetic field extends out of the field generation portion;
a plasma processing chamber configured to receive the ionizing electromagnetic field and configured to contain the plasma, wherein the plasma is sustained by the ionizing electromagnetic field, and wherein the ionizing electromagnetic field is attenuated en route to the plasma processing chamber;
a substrate support positioned within the plasma processing chamber and disposed to support a substrate;
a controllable DC power supply to provide a DC voltage that is fixed in magnitude in response to a setting for a monoenergetic distribution of ion energy at the surface of the substrate;
two switching components and a controller to alternately couple a ground potential and the DC voltage to the substrate support to apply a voltage waveform to the substrate support that includes a positive voltage peak followed by a drop in voltage to the ground potential, wherein the drop in the voltage effectuates a negative voltage at the surface of the substrate that prompts ion current in the plasma processing chamber;
a DC current source coupled to the substrate support to provide compensation current to the substrate support to compensate for the tendency of the ion current in the plasma processing chamber to change the voltage at the surface of the substrate in order to maintain the negative voltage level at the surface of the substrate;
a voltage monitor coupled to the substrate support to monitor the voltage waveform applied to the substrate support;
a compensation current controller coupled to the DC current source to fix, based upon the monitored voltage, the compensation current provided to the substrate support to maintain the negative voltage level at the surface of the substrate.
2. The system of claim 1 further comprising a field projection portion coupled between the field generation portion and the plasma processing chamber, wherein the field projection portion attenuates the ionizing electromagnetic field as it passes through the field projection portion.
3. The system of claim 2 , wherein the field projection portion controllably attenuates the ionizing electromagnetic field via a controllable electrical bias applied to the field projection portion.
4. The system of claim 1 , wherein the two switching components are DC-coupled to the substrate support.
5. The system of claim 1 , including an additional power supply coupled to the substrate support, the additional power supply adapted to apply power to the substrate support so as to sustain the plasma in the plasma processing chamber.
6. The system of claim 1 , wherein the ionizing electromagnetic field extends to the plasma processing chamber as a result of a potential difference between the field generation portion and the plasma processing chamber.
7. The system of claim 1 , wherein a non-activated gas is fed into the plasma processing chamber and converted at least in part into first radicals by the ionizing electromagnetic field.