High-accuracy pattern shape evaluating method and apparatus
View Patent ↗A quantity (or dispersion value) of a distribution of edge position due to random noise is expected to be reduced statistically to 1/N when N edge position data items are averaged. Using this property, the single page image is averaged in a vertical direction with various values of parameter S, and then the edge roughness index is calculated. The S-dependence of the edge roughness index is analyzed and a term of a dispersion value directly proportional to 1/S is determined as being due to noise.
1. A pattern shape evaluating apparatus comprising:
a scanning electron microscope detecting a secondary electron or reflected electron by irradiation of an electron beam to a specimen formed with line pattern, and retrieving a two-dimensional distribution data of the secondary electron signal or the reflected electron signal; and
a data processing apparatus for processing the two-dimensional distribution data;
wherein the data processing apparatus retrieves a plurality of edge points data of the line pattern from the two-dimensional distribution data;
generates data set of the edge points with different averaging parameter that defines a range of averaging to longitudinal direction of the line pattern, by calculating an averaging process to the data set within a range defined by the averaging parameter;
calculating a standard deviation of the roughness of the data set corresponding to each averaging parameter; and
calculating a noise-caused bias of the roughness included based on a relationship between the standard deviation and the averaging parameter.
2. The pattern shape evaluating apparatus according to claim 1 , said data processing apparatus calculates a real value and the noise-caused bias by fitting the standard deviation with the real value and the bias as fitting parameters.
3. The pattern shape evaluating apparatus according to claim 1 , further comprising:
a monitor for displaying the noise-caused bias.
4. The pattern shape evaluating apparatus according to claim 3 , wherein said monitor displays a request for the averaging parameter;
said data processing apparatus carries out the averaging process within a range defined by the entered value of the averaging process.
5. The pattern shape evaluating apparatus according to claim 4 , wherein said data processing apparatus compensate the data set that is dropped in the averaging process.
6. The pattern shape evaluating apparatus according to claim 5 , further comprising:
a storage means for storing first two-dimensional distribution data for the compensation;
wherein said monitor displays an image of the first two-dimensional distribution data and a request for selecting an area in the image,
said data processing apparatus calculates parameters used for the compensation using the first two-dimensional distribution data.
7. The pattern shape evaluating apparatus according to claim 6 , wherein the storage means stores the second two-dimensional distribution data obtained at a higher magnification than the first two-dimensional distribution data; and
the data processing apparatus carries out the compensating operation on the data set of standard deviations calculated from the second two-dimensional distribution data, using the parameters calculated based on the first two-dimensional distribution data.
8. The pattern shape evaluating apparatus according to claim 5 , wherein the data processing apparatus stores a plurality of different algorithms for the compensation.
9. The pattern shape evaluating apparatus according to claim 6 , wherein said monitor displays CAD data corresponding to the selected area as the first two-dimensional distribution data.
10. A critical dimension measurement SEM equipped with a function calculating a roughness, including:
a scanning electron microscope for obtaining a data set of edge points used for the calculation of the roughness;
a data processing apparatus that calculates a roughness;
wherein said data processing apparatus has function comprised of:
averaging the edge points within a range defined by a predetermined averaging parameter;
calculating a standard deviation of the roughness using the data set of the averaged edge points;
calculating a relationship between the standard deviation and the averaging parameter; and
calculating a noise-caused bias in the roughness based on the relationship between the standard deviation and the averaging parameter.
11. The critical dimension measurement SEM according to claim 10 , said function of the data processing apparatus further comprising:
calculating a real value and the noise-caused bias by fitting the standard deviation with the real value and the bias as fitting parameters.
12. The critical dimension measurement SEM according to claim 10 , further comprising:
a monitor for displaying the noise-caused bias.
13. The critical dimension measurement SEM according to claim 12 , wherein said monitor displays a request for the averaging parameter;
said function of the data processing apparatus further comprising:
calculating the averaging process within a range defined by the entered value of the averaging parameter.
14. The critical dimension measurement SEM according to claim 13 , said function of the data processing apparatus further comprising:
compensating the data set that is dropped in the averaging process.
15. The critical dimension measurement SEM according to claim 14 , further comprising:
a storage means for storing the first two-dimension distribution data for the compensation;
wherein said monitor displays an image of the first two-dimensional distribution data and a request for selecting an area in the image,
said function of the data processing apparatus further comprising:
calculating parameter used for the compensation using the first two-dimensional distribution data.
16. The critical dimension measurement SEM according to claim 15 , wherein the storage means stores the second two-dimensional distribution data obtained at a higher magnification than the first two-dimensional distribution data;
said function of the data processing apparatus further comprising:
compensating the data set of standard deviations calculated from the second two-dimensional distribution data with using the parameters calculated based on the first two-dimensional distribution data.
17. The critical dimension measurement SEM according to claim 14 , wherein the data processing apparatus stores a plurality of different algorithms for the compensation.
18. The critical dimension measurement SEM according to claim 15 , wherein said monitor displays CAD data corresponding to the selected area as the first two-dimensional distribution data.