Metrology system with spectroscopic ellipsometer and photoacoustic measurements
View Patent ↗An optical system includes both a microspot broadband spectroscopic ellipsometer and a photoacoustic film thickness measurement system that are supplied laser light by the same laser light source. One of the systems makes a measurement, the result of which is used to adjust a parameter of the other system; e.g. the ellipsometer measures thickness and the photoacoustic system uses the thickness result to measure the speed of sound. In one version, the ellipsometer converts the laser beam to a broad-spectrum beam that provides higher intensity.
1. A method of manufacturing a semiconductor device using a damascene process comprising:
selecting a site on a semiconductor substrate for measurement of a damascene structure formed on the substrate, where the damascene structure comprises at least one metal filled trench formed into the substrate and the trench is bounded on at least one side by a dielectric material;
using one of an ellipsometer and a photoacoustic system to measure a value of a first parameter of the damascene structure at the selected site;
using the other of the ellipsometer and the photoacoustic system to measure a value of a second parameter of the damascene structure at the selected site; and
calculating an output parameter based at least in part on the first and second parameters, where the output parameter is correlated to a physical characteristic of the damascene structure of the substrate that has been modified by a polishing process.
2. The method of claim 1 wherein the output parameter is a thickness of one of the at least one metal filled trench formed into the substrate.
3. The method of claim 1 wherein the output parameter is a thickness of the dielectric material.
4. The method of claim 1 , wherein the output parameter is indicative of a variation between a thickness of one of the at least one metal filled trench and a thickness of the dielectric material.
5. The method of claim 1 , wherein the output parameter is a ratio of the thicknesses of one of the at least one metal filled trench and the dielectric material.
6. The method of claim 1 , wherein the ellipsometer is used to measure a parameter of the dielectric material and the photoacoustic system is used to measure a parameter of one of the at least one metal filled trench.
7. The method of claim 1 , wherein the ellipsometer is used to measure a parameter of one of the at least one metal filled trench and the photoacoustic system is used to measure the same parameter of the metal filled trench, the two values of the parameter of the one of the at least one metal filled trench being combined to obtain an improved parameter value.
8. The method of claim 7 , wherein the two parameter values comprise a weighted average.
9. The method of claim 1 , further comprising obtaining, using at least one of the ellipsometer and the photoacoustic system, at least one parameter of a film stack of which the damascene structure forms a part and calculating a difference between the at least one parameter and the output parameter, the difference correlating to a relationship between the physical characteristic of the damascene structure and a physical characteristic of one of the at least one metal filled trench.
10. The method of claim 9 , wherein the physical characteristic of the damascene structure is a thickness and the physical characteristic of the film stack is a thickness.
11. The method of claim 1 , further comprising modifying the polishing process based at least in part on the output parameter.
12. The method of claim 11 , further comprising:
calculating a ratio between the output parameter and the at least one parameter, the ratio being indicative of a cumulative action of the polishing process on the film stack; and
modifying the polishing process based at least in part on the ratio.
13. The method of claim 11 , where the polishing process is a chemical-mechanical polishing process.
14. The method of claim 1 , where using the other of the ellipsometer and the photoacoustic system further comprises measuring a value of a second at least one additional parameter.
15. The method of claim 1 , where using one of an ellipsometer and a photoacoustic system further comprises measuring a value of a first at least one additional parameter.
16. A semiconductor device fabricated according to the method of claim 1 .