ICP source for M and W-shape discharge profile control
Apparatuses and methods are provided that, in some embodiments use an adjustable middle coil to tune plasma density in a plasma processing system. For example, in one embodiment, a plasma processing apparatus includes an impedance match circuit coupled to an Rf power source. The impedance match circuit measures voltage and current at an inner and an outer coil. The match circuit calculates plasma density from the measured voltage and/or current. An adjustable middle coil located between the inner and outer coils is adjusted and/or replaced to tune the plasma density radial profile.
1. A plasma processing apparatus, comprising:
a chamber lid and a chamber body enclosing a processing region;
an inner coil disposed above the processing region;
an outer coil disposed about the processing region and the inner coil;
an adjustable middle coil between the inner coil and the outer coil wherein the adjustable middle coil has a resonance frequency at one set of input parameters and is replaceable with a different middle coil that has a different resonant frequency at the one set of input parameters;
an impedance match circuit coupled to the inner coil and the outer coil; and
an Rf generator coupled to the impedance match circuit.
2. The plasma processing apparatus of claim 1 wherein the adjustable middle coil is coupled to a capacitor to adjust resonant frequency of the adjustable middle coil.
3. The plasma processing apparatus of claim 1 wherein the adjustable middle coil is at least one wind of conductive material.
4. The plasma processing apparatus of claim 1 wherein the adjustable middle coil is coupled to an adjustable capacitor to adjust resonant frequency of the adjustable middle coil.
5. The plasma processing apparatus of claim 1 wherein a diameter of the adjustable middle coil is adjustable with respect to a diameter of the inner coil and a diameter of the outer coil.
6. The plasma processing apparatus of claim 1 wherein distance of the adjustable middle coil from the chamber lid is adjustable.
7. A method comprising:
selecting a radial plasma density non-uniformity value;
selecting a capacitor value for a variable capacitor coupled to an adjustable middle coil;
switching a plasma source ON;
measuring line integrated plasma emissivity; and
calculating a radial plasma density profile;
calculating a radial plasma density non-uniformity from the plasma density profile;
comparing the calculated radial plasma density non-uniformity to the selected radial plasma density non-uniformity value, and
adjusting the variable capacitor, to increase the calculated radial plasma density non-uniformity, until the selected radial plasma density non-uniformity value is one of greater than the calculated radial plasma density non-uniformity and equal to the calculated radial plasma density non-uniformity.
8. The method of claim 7 wherein the selecting of the radial plasma density non-uniformity value further comprises at least one of:
altering a distance of the adjustable middle coil from a chamber lid;
altering a diameter of the adjustable middle coil to change a radius of power deposition in plasma from the adjustable middle coil; and
replacing the adjustable middle coil with a different adjustable middle coil.
9. The method of claim 7 wherein the line integrated plasma emissivity is measured using an ion energy distribution sensor and optical emission spectroscopy.
10. The method of claim 7 wherein the calculated radial plasma density profile is calculated using Abel Inversion.
11. The method of claim 7 wherein the calculated radial plasma density non-uniformity is calculated using a maximum plasma density over a substrate and a minimum plasma density over the substrate.
12. A method comprising:
selecting a radial plasma density non-uniformity value;
selecting a capacitor value for a variable capacitor coupled to an adjustable middle coil;
switching a plasma source ON;
checking a current ratio between an inner coil and an outer coil;
checking a look-up table for a stored current ratio and a stored radical plasma density non-uniformity associated with the stored current ratio that is similar to the checked current ratio;
comparing the stored radical plasma density non-uniformity to the selected radial plasma density non-uniformity value, and
adjusting the variable capacitor, to increase the calculated radial plasma density non-uniformity, until the selected radial plasma density non-uniformity value is one of greater than the calculated radial plasma density non-uniformity and equal to the calculated radial plasma density non-uniformity.
13. The method of claim 12 wherein the current ratio is checked at a source match output.
14. The method of claim 13 wherein a power coupling to plasma of the adjustable middle coil is changed by altering a distance of the adjustable middle coil from a chamber lid.
15. The method of claim 13 wherein a diameter of power coupling to the plasma of the adjustable middle coil is changed by altering the diameter of the adjustable middle coil.
16. The method of claim 13 wherein the resonant frequency, of the adjustable middle coil, is changed by adjusting capacitance of a variable capacitor coupled to the adjustable middle coil.
17. The method of claim 12 further comprising replacing the adjustable middle coil with a different adjustable middle coil.
18. The method of claim 12 further comprising replacing the adjustable middle coil with a different adjustable middle coil after at least one of:
adjusting capacitance of a variable capacitor coupled to the adjustable middle coil;
altering a distance of the adjustable middle coil from a chamber lid; and
altering the diameter of the adjustable middle coil.