Methods and systems for monitoring state of plasma chamber

1. A method of monitoring a plasma chamber, comprising:

measuring an optical characteristic of plasma in a predetermined measurement wavelength band, the plasma being generated in the plasma chamber including a window;

extracting a process status index (PSI) from the measured optical characteristic; and

evaluating a state of the plasma chamber by analyzing the extracted PSI,

wherein the optical characteristic of the plasma is measured in the predetermined measurement wavelength band in which a transmittance of light passing through the window is substantially independent of a wavelength of the light.

2. The method of claim 1 , wherein the optical characteristic of the plasma is measured in the predetermined measurement wavelength band in which a transmittance of light passing through the window varies in a range from about 1% to about 20% according to a wavelength of the light.

3. The method of claim 1 , wherein the measuring of the optical characteristic comprises measuring light emitted from the plasma chamber, the light having a wavelength in a range from about 900 nm to about 1700 nm.

4. The method of claim 1 , wherein the measuring of the optical characteristic comprises measuring a spectral characteristic of light emitted from the plasma chamber in a range of wavelength from about 600 nm to about 3000 nm.

5. The method of claim 1 , wherein the predetermined measurement wavelength band is a band in which a transmittance variation of light passing through the window is substantially independent of a thickness of a by-product deposited on the window.

6. The method of claim 1 , wherein the extracting of the PSI comprises performing an inner product of data of the optical characteristic and wavelength-weight data, wherein the wavelength-weight data are obtained by principal component analysis (PCA) or multi-way principal component analysis (MPCA).

7. The method of claim 6 , wherein the extracting of the PSI further comprises normalizing intensity values of light measured in the predetermined measurement wavelength band based on an intensity value of light measured at a predetermined reference wavelength, prior to the performing of the inner product.

8. The method of claim 1 , wherein the evaluating of the state of the plasma chamber comprises comparing the PSI with PSI trend data to provide information about a variation trend of the PSI with respect to time.

9. The method of claim 8 , wherein the evaluating of the state of the plasma chamber further comprises transmitting a signal to an operator to inform the operator of a process error when a difference between the PSI and the PSI trend data is equal to or greater than a predetermined critical value.

10. The method of claim 9 , wherein the evaluating of the state of the plasma chamber comprises disregarding a variation of the PSI caused by an intended process condition change by evaluating the variation of the PSI using condition-result data providing information about a relationship between process condition changes and variations of the PSI.

11. A system for monitoring a plasma chamber, comprising:

a measurement unit configured to measure light emitted from the plasma chamber through a window of the plasma chamber in a predetermined measurement wavelength band;

a process status index (PSI) extraction part configured to extract a PSI from an optical characteristic of the light; and

a status decision part configured to evaluate a state of the plasma chamber by analyzing the extracted PSI,

wherein the predetermined measurement wavelength band is a band in which a transmittance of light passing through the window is substantially independent of a wavelength of the light.

12. The system of claim 11 , wherein the predetermined measurement wavelength band is a band in which a transmittance of light passing through the window varies in a range from about 1% to about 20% according to a wavelength of the light.

13. The system of claim 12 , wherein the predetermined measurement wavelength band ranges from about 900 nm to about 1700 nm.

14. The system of claim 11 , wherein the predetermined measurement wavelength band ranges from about 600 nm to about 3000 nm.

15. The system of claim 11 , wherein the predetermined measurement wavelength band is a band in which a transmittance variation of light passing through the window is substantially independent of a thickness of a by-product deposited on the window.

16. The system of claim 11 , wherein the PSI extraction part comprises a first processing part configured to convert intensity values of light measured in the predetermined measurement wavelength band into ratios to an intensity value of light measured at a predetermined reference wavelength.

17. The system of claim 16 , wherein the PSI extraction part further comprises a second processing unit configured to calculate an inner product of wavelength-weight data and intensity values of light measured in the measurement wavelength band, wherein the wavelength-weight data are data obtained by principal component analysis (PCA) or multi-way principal component analysis (MPCA) for assigning different weights to the measured intensity values according to wavelength.

18. The system of claim 11 , wherein the status decision part is configured to evaluate the state of the plasma chamber by comparing the PSI with PSI trend data providing information about a variation trend of the PSI with respect to time.

19. The system of claim 18 , further comprising a user interface configured to transmit a signal to an operator to inform the operator of a process error when a difference between the PSI and the PSI trend data is equal to or greater than a predetermined critical value.

20. The system of claim 19 , wherein the status decision part is configured to disregard a variation of the PSI caused by an intended process condition change by evaluating the variation of the PSI using condition-result data providing information about a relationship between process condition changes and variations of the PSI.