Electrical sensor for real-time feedback control of plasma nitridation
View Patent ↗A device ( 101 ) for controlling the treatment of a substrate ( 102 ) with a plasma ( 103 ) is provided which comprises (a) a plasma chamber ( 104 ) adapted to generate a plasma ( 103 ); (b) a sensor ( 113 ) equipped with first ( 115 ) and second ( 117 ) electrodes that are exposed to the plasma generated within the chamber, said sensor being adapted to (i) apply a first low frequency voltage V 1 to the first electrode, (ii) apply a plurality of high frequency voltages V 2 . . . V n to the first electrode, where n≧2, and (iii) measure the respective currents I 1 . . . I n flowing through the second electrode during application of each of the voltages V 1 . . . V n , respectively; and (c) a data processing device ( 121 ) adapted to determine the densities of a plurality of ion species based on currents I 1 . . . I n and on a mathematical model or on calibration data relating to the plasma chamber.
1. A method for quantitatively determining species density in a plasma during treatment of a substrate with the plasma in a plasma chamber equipped with first and second electrodes, comprising:
applying a plurality of voltages V 1 . . . V n to the first electrode, wherein n≧2, wherein V 1 is a low frequency voltage, and wherein V 2 . . . V n are high frequency voltages;
measuring the respective currents I 1 . . . I n flowing through the second electrode during application of each of the voltages V 1 . . . V n , respectively; and
using the currents I 1 . . . I n to determine the density of an individual ion species in the plasma.
2. The method of claim 1 , wherein the currents I 1 . . . I n are used in conjunction with a mathematical model or calibration data to determine the density of an individual ion species in the plasma.
3. The method of claim 1 , wherein V 1 . . . V n are low amplitude voltages.
4. The method of claim 1 , further comprising adjusting at least one parameter of the plasma treatment based on the determined density of at least one ion species.
5. The method of claim 1 , wherein the voltage V 1 has a frequency of less than 1 MHz.
6. The method of claim 1 , wherein the voltage V 1 has a frequency within the range of about 150 to about 300 kHz.
7. The method of claim 1 , wherein each of the voltages V 2 . . . V n has a frequency within the range of about 1 to about 30 MHz.
8. The method of claim 1 , wherein the currents I 1 . . . I n are used to determine the density in the plasma of an ion species selected from the group consisting of N 2 + , N + , He + , Ar + , Ne + , Xe + , Kr + , O 2 + and O + .
9. The method of claim 1 , wherein the currents I 1 . . . I n are used to determine the density in the plasma of both N 2 + and N + .
10. The method of claim 9 , wherein the density of at least one neutral species in the plasma is also determined.
11. The method of claim 1 , wherein n=2.
12. The method of claim 1 , wherein the substrate is a gate oxide.
13. The method of claim 12 , wherein the treatment is a nitridation treatment.
14. The method of claim 1 , wherein V 1 is used to determine total ion density in the plasma, and wherein at least one of V 2 . . . V n is used to determine the density of an individual ion in the plasma.
15. The method of claim 1 , wherein the species density in the plasma is determined during treatment of a substrate with the plasma.
16. The method of claim 1 , wherein the voltages V 1 . . . V n giving rise to currents I 1 . . . I n are applied to the same plasma.