System and method for via structure measurement
A system for via structure measurement is disclosed. The system comprises a reflectometer, a simulation unit and a comparing unit. The reflectometer is configured to collect a measured diffraction spectrum of at least a via. The simulation unit is configured to provide simulated diffraction spectrums of the at least a via. The comparing unit is configured to determine at least a depth and at least a bottom profile of the at least a via by comparing the collected diffraction spectrum and the simulated diffraction spectrums.
1. A method for determining via structure parameters according to a diffraction spectrum of at least a via structure, comprising the steps of:
obtaining a measured diffraction spectrum of at least a via structure;
carrying out a calculation based upon frequency information contained in the measured diffraction spectrum; and
determining at least a depth of the at least a via structure according to the calculation results.
2. The method of claim 1 , wherein the measured diffraction spectrum comprises a high-frequency portion and a low-frequency portion, the low-frequency portion serves as the carrier frequency of the high-frequency portion, the calculation is based upon the high-frequency portion, and the at least a depth of the at least a via structure is determined according to the calculation results based upon the high-frequency portion.
3. The method of claim 2 , wherein the calculation is also based upon the low-frequency portion, and a thickness of an oxide layer on the surface of each of the at least a via structure is determined according to the calculation results based upon the low-frequency portion.
4. The method of claim 1 , wherein the calculation is carried out by comparing the measured diffraction spectrum with a plurality of simulated diffraction spectrums corresponding to the at least a via structure obtained according to Fresnel equation, the determination step is applied to select a simulated diffraction spectrum with a minimum difference compared with the measured diffraction spectrum, and then to determine the at least a depth of the at least a via structure according to the parameters of the selected simulated diffraction spectrum.
5. The method of claim 1 , wherein the calculation is carried out by performing a Fourier transform of the measured diffraction spectrum, and the at least a depth of the at least a via structure is determined according to the calculation results of the Fourier transform.
6. The method of claim 1 , wherein the measured diffraction spectrum is obtained by operating a reflectometer on the at least a via structure.
7. The method of claim 6 , wherein the measured diffraction spectrum is obtained by operating a reflectometer on a plurality of via structures simultaneously, and the depths of the via structures are determined simultaneously.
8. A method for determining the bottom profile of at least a via structure according to the reflection spectrums of the at least a via structure, comprising the steps of:
obtaining a measured diffraction spectrum of the at least a via structure;
carrying out a calculation based upon magnitude information contained in the measured diffraction spectrum; and
determining at least a bottom profile of the at least a via structure according to the calculation results.
9. The method of claim 8 , wherein the measured diffraction spectrum comprises a high-frequency portion and a low-frequency portion, the low-frequency portion serves as the carrier frequency of the high-frequency portion, the calculation is based upon the magnitude of the high-frequency portion relative to the low-frequency portion, and the at least a bottom profile of the at least a via structure is determined according to the calculation results based upon the magnitude of the high-frequency portion relative to the low-frequency portion.
10. The method of claim 8 , wherein the calculation is carried out by comparing the measured diffraction spectrum with a plurality of simulated diffraction spectrums corresponding to the at least a bottom profile of the at least a via structure obtained according to Fresnel equation and an ellipsoid model, the determination step is performed to select a simulated diffraction spectrum with a minimum difference compared with the measured diffraction spectrum, and then the at least a bottom profile of the at least a via structure is determined according to the parameters of the selected simulated diffraction spectrum.
11. The method of claim 10 , wherein the longitudinal section of the ellipsoid model is an ellipse, which can be represented by the following equation:
x
2
a
2
+
y
2
b
2
=
1
where a, which is a known parameter, is the semimajor axis of the ellipse and is the radius of the at least a via structure, b is the semiminor axis of the ellipse, and the determination step is performed to determine the parameter b and thus determine the at least a bottom profile of the at least a via structure.
12. The method of claim 10 , wherein the radius of the at least a via structure is obtained according to measurement or manufacture parameters.
13. The method of claim 8 , wherein the measured diffraction spectrum is obtained by operating a reflectometer on the at least a via structure.
14. The method of claim 13 , wherein the measured diffraction spectrum is obtained by operating a reflectometer on a plurality of via structures simultaneously, and the bottom profiles of the via structures are determined simultaneously.
15. A system for via structure measurement, comprising:
a reflectometer, configured to collect a measured diffraction spectrum of at least a via structure;
a simulation unit, configured to provide simulated diffraction spectrums of the at least a via structure; and
a comparing unit, configured to determine at least a depth and at least a bottom profile of the at least a via structure by comparing the collected measured diffraction spectrum of at least a via structure and the simulated diffraction spectrums of the at least a via structure.
16. The system of claim 15 , wherein the simulation unit is a database, which stores a plurality of simulated diffraction spectrums of via structures with different depths and different bottom profiles.
17. The system of claim 15 , wherein the simulation unit is a computer, which is configured to generate simulated diffraction spectrums of via structures with different depths and different bottom profiles.
18. The system of claim 15 , wherein the simulated diffraction spectrums of the at least a via structure are generated based upon Fresnel equation.
19. The system of claim 15 , wherein the simulated diffraction spectrums of the at least a via structure are generated according to an ellipsoid model, which simulates the at least a bottom profile of the at least a via structure.
20. The system of claim 19 , wherein the longitudinal section of the ellipsoid model is an ellipse, which can be represented by the following equation:
x
2
a
2
+
y
2
b
2
=
1
where a, which is a known parameter, is the semimajor axis of the ellipse and is the radius of the at least a via structure, b is the semiminor axis of the ellipse, and the comparing unit is configured to determine the parameter b and thus determine the at least a bottom profile of the at least a via structure.
21. The system of claim 20 , wherein the radius of the at least a via structure is obtained according to measurement or manufacture parameters.