Method for acquiring high-resolution images of defects on the upper surface of the wafer edge
A method for acquiring high-resolution images of defects on the upper surface of the wafer edge is disclosed. For this purpose, first the position of at least one defect on the upper surface of the wafer edge is determined. The thus determined position of the defect is stored. Then the wafer is transferred into device for micro-inspection, in which the defect is examined more closely and imaged. The images acquired in the device for micro-inspection are deposited in a directory.
1. A method for acquiring high-resolution images of defects on an upper surface of a wafer edge, comprising the steps of:
providing a position of at least one defect on the upper surface of the wafer edge;
transferring the wafer into a device for micro-inspection;
focusing on each defect in the device for micro-inspection, wherein an appropriate focusing method is selected depending on the position of the defect with respect to the wafer edge;
imaging the at least one defect in the device for micro-inspection using a microscope including several objectives of various magnifications, wherein a first objective most suitable for detecting the defect is selected for imaging; and
depositing images of the at least one defect in a directory.
2. The method of claim 1 , wherein the position of the defect with respect to the wafer edge is determined by a radius set by a user.
3. The method of claim 1 , wherein providing the position of at least one defect is performed via a review file.
4. The method of claim 1 , wherein providing the position of at least one defect is performed by a device for macro-inspection.
5. The method of claim 4 , wherein the whole surface of the wafer is captured with the device for macro-inspection.
6. The method of claim 4 , wherein the wafer is transported into the device for edge inspection for determining the position of the at least one defect on the upper surface of the wafer edge, and that the position of the at least one defect is determined in the device for edge inspection.
7. The method of claim 1 , wherein a laser focus is used for defects that, for a predetermined value of the radius, are located nearer to the center of the wafer.
8. The method of claim 1 , wherein a TV focus is used for defects that, for a predetermined value of the radius, are located further from the center of the wafer.
9. The method of claim 1 , wherein, for defects that, for a predetermined value of the radius, are located nearer to the edge of the wafer, first an X/Y position is taken up that is located in the proximity of the actual defect but nearer to the center of the wafer, that the laser focus is used for focusing at this position, that the laser focus is turned off, and that there is a return to the defect with this focus setting.
10. The method of claim 1 , wherein, for defects that, for a predetermined value of the radius, are located nearer to the edge of the wafer, first an X/Y position is taken up that is located in the proximity of the actual defect but nearer to the center of the wafer, that the laser focus is used for focusing at this position, that the laser focus is turned off, that a TV focus is moved to some distance from the focal position of the laser focus, and that several images are acquired in an interval around the focal position of the laser focus.
11. The method of claim 1 , wherein an automatic alignment of the wafer is performed in the device for micro-inspection.
12. The method of claim 11 , wherein the automatic alignment is performed with a bare wafer.
13. The method of claim 11 , wherein the automatic alignment is performed with a structured wafer.
14. The method of claim 1 , wherein a scan performing automatic defect centering is added upstream in the device for micro-inspection if the defect is located outside a field of view of a currently used objective because of the imprecise position determination in the device for macro-inspection, and wherein the defect position is not determined with the help of reference images, but with the defect image itself.
15. The method of claim 14 , wherein a Z drive is moved with constant speed, and that images are acquired and evaluated during the movement.
16. The method of claim 15 , wherein, when a definition criterion is reached or after a Z interval has been completed, the Z position stored at the beginning is taken up again, and that the best image with respect to definition is stored.
17. The method of claim 1 , wherein the wafer is returned into the cartridge connected to a system for optical inspection of wafers after the scan has been completed, and the acquired images of the defects are stored in a directory to be chosen by the user.
18. The method of claim 17 , wherein the images are deposited as reference in a KLA Review File.