Testing apparatus using charged particles and device manufacturing method using the testing apparatus
A substrate is irradiated by primary electrons and secondary electrons generated from the substrate are detected by a detector. A reference die is placed on the stage to obtain a pattern matching template image including feature coordinates of the reference die. A pattern matching is performed with an arbitrary die in a row or column including the reference die using the template image to obtain feature coordinates of the arbitrary die. An angle of misalignment is calculated between the direction of the row or column including the reference die and one of the directions of movement of the substrate on the basis of the feature coordinates of the arbitrary die and those of the reference die. The stage is rotated to correct the angle of misalignment to conform the direction of the row or column including the reference die with the one of the directions of movement of the substrate.
1. A method of inspecting a substrate having dies arranged in matrix, wherein the substrate is irradiated by primary electrons and secondary electrons generated from the substrate is detected by a detector, the method comprising:
(a) placing the substrate on a stage;
(b) selecting a reference die from among the dies placed on the stage to obtain a pattern matching template image including feature coordinates of the reference die;
(c) performing pattern matching with an arbitrary die in a row or column including the reference die using the template image to obtain feature coordinates of the arbitrary die;
(d) calculating an angle of misalignment between the direction of the row or column including the reference die and one of the directions of movement of the substrate on the basis of the feature coordinates of the arbitrary die and those of the reference die;
(e) rotating the stage to correct the angle of misalignment to conform the direction of the row or column including the reference die with the one of the directions of movement of the substrate;
(f) after step (e), rotating the detector to conform the one of the directions of movement of the substrate with a direction of scan of the detector; and
(g) after step (f), irradiate the substrate with the primary electrons.
2. The method of claim 1 , further comprising:
prior to step (a), disposing means for irradiating the substrate with electrons, the stage and the detector within a vacuum container,
wherein step (f) is performed by a rotation mechanism disposed outside of the vacuum container.
3. The method of claim 2 , wherein the vacuum container comprises a first barrel and a second barrel rotatably supported against the first barrel and having the detector and wherein the rotation mechanism is structured to rotate the second barrel.
4. The method of claim 1 , wherein steps (a)-(g) are performed in a projection mapping type electron beam apparatus wherein a primary electron beam having two-dimensional cross section irradiates the substrate to detect by the detector a secondary electron beam having information of a surface of the substrate.
5. The method of claim 4 , wherein the electron beam apparatus comprises a beam separator (E×B) and wherein the direction of electric field of the E×B is conformed with the direction of scan of the detector.
6. The method of claim 5 , further comprising:
after step (e) and prior to step (f), moving a numerical aperture (NA) device to an optically optimum position in accordance with a change in magnification of the electron beam apparatus.
7. The method of claim 2 , wherein steps (a)-(g) are performed using an optical microscope having a high magnification after steps (a)-(g) are performed using an optical microscope having a low magnification.
8. The method of claim 1 , wherein step (b) comprises repeatedly performing:
estimating feature coordinates of a next arbitrary die on the basis of a positional relation between the feature coordinates of the reference die and accurate feature coordinates of the arbitrary die obtained by the pattern matching of the template image;
performing pattern matching using the template image near the estimated feature coordinates; and
obtaining accurate feature coordinates of the next arbitrary die.
9. The method of claim 8 , wherein the repeatedly performing comprises:
repeatedly estimating the feature coordinates of the next arbitrary die on the basis of a positional relation between the feature coordinates of the reference die and the feature coordinates of the die obtained in the step just before.
10. The method of claim 1 , further comprising:
obtaining a size in the direction perpendicular to the row or column used for obtaining the angle of displacement; and
producing a die map on the basis of the obtained size.
11. The method of claim 10 , wherein the obtaining a size comprises:
selecting a reference die to obtain a pattern matching template image including feature coordinates of the reference die;
performing pattern matching, using the template image, to an arbitrary die located on a row or column in a direction perpendicular to the row or column based on which the angle of displacement is obtained to obtain feature coordinates of the arbitrary die; and
obtaining a distance between the feature coordinates of the reference die and those of the arbitrary die and the number of dies included within the distance to obtain a size of a die in a direction perpendicular to the row or column based on which the angle of displacement is obtained.
12. The method of claim 1 , further comprising:
obtaining a difference between a target position of the stage and an actual position thereof to apply, across electrodes for deflecting the electrons, a correction voltage operable to cancel the obtained difference.
13. The method of claim 1 , wherein the secondary electrons comprises any one of electrons produced from the substrate, reflected electrons and back scattered electrons.
14. The method of claim 1 , wherein the secondary electrons comprises mirror electrons reflected in the vicinity of a surface of the substrate.