System and method for controlling plasma density
This disclosure relates to a plasma processing system for controlling plasma density near the edge or perimeter of a substrate that is being processed. The plasma processing system may include a plasma chamber that can receive and process the substrate using plasma for etching the substrate, doping the substrate, or depositing a film on the substrate. This disclosure relates to a plasma processing system that may include a power electrode that may be opposite a bias electrode and a focus ring electrode that surrounds the substrate. In one embodiment, the power electrode may be coupled to a direct current (DC) source. Power applied to the bias electrode may be used to draw ions to the substrate. The plasma density may be made more uniform by applying a focus ring voltage to the focus ring that is disposed around the substrate and/or the bias electrode.
1. A method for treating a substrate in a plasma processing system, comprising:
receiving the substrate on a bias electrode within a plasma processing chamber;
applying a source voltage to a power electrode that is opposite the bias electrode;
applying, through a power control circuit, a bias voltage to the bias electrode that is subjacent to the substrate;
applying, through the power control circuit, a focus ring voltage to a focus ring that is in direct contact with an edge of the substrate, the focus ring voltage being less than the bias voltage; and
generating a plasma by igniting gas within the plasma processing chamber using at least the power electrode,
wherein the power control circuit includes (i) a power source connected in parallel with a first variable capacitor, (ii) a matching capacitor and a matching inductor connected in series with the power source and the first variable capacitor, and (iii) a second variable capacitor having a first end connected to the focus ring and a second end connected to the matching inductor,
wherein the power source includes a first end connected to a ground and the variable capacitor includes a first end connect to a ground, and
wherein the power source includes a second end connected to the matching capacitor and the variable capacitor includes a second end connected to the matching capacitor.
2. The method of claim 1 , wherein the focus ring voltage comprises a magnitude that is at least 50V less than the bias voltage.
3. The method of claim 2 , wherein the applying of the power electrode comprises a magnitude between 0 volts and 10,000 volts.
4. The method of claim 1 , wherein the focus ring voltage comprises a magnitude that is between 100V and 800V less than the bias voltage.
5. The method of claim 1 , wherein the focus ring voltage comprises a magnitude that is at least 5% less than the bias voltage.
6. The method of claim 1 , wherein the gas comprises a halogen-containing gas, a noble-containing gas, an oxygen-containing gas, or a combination thereof.
7. The method of claim 1 , wherein the receiving comprises coupling the substrate to the bias electrode using an electrostatic component.
8. The method of claim 1 , wherein the focus ring voltage comprises a magnitude that is less than the bias voltage by a value that is greater than 500V and less than or equal to 800V.
9. The method of claim 1 , wherein the focus ring voltage is applied directly to the focus ring.
10. The method of claim 1 , wherein the bias electrode is in direct contact with the substrate.