Method for reticle inspection using aerial imaging
First Claim
1. A method for inspecting a multiple die reticle that is used with an optical exposure system under a set of exposure conditions, said multiple die reticle including at least a first die and a second die, said method comprising:
- acquiring a plurality of aerial images of said reticle using a transmitted light, said plurality of aerial images being acquired within a process window of said exposure system and using said set of exposure conditions;
said plurality of aerial images including a first plurality of aerial images of said first die and a second plurality of aerial images of said second die; and
comparing said first plurality of aerial images of said first die and said second plurality of aerial images of said second die to detect variations in line width in said first die.
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Accused Products
Abstract
A reticle inspection system for inspecting reticles can be used as an incoming inspection tool, and as a periodic and pre-exposure inspection tool. Mask shops can use it as an inspection tool compatible to their customers, and as a printable error detection tool. The inventive system detects two kinds of defects: (1) line width errors in the printed image; (2) surface defects. The line width errors are detected on the die area. The detection is performed by acquiring the image of the reticle under the same optical conditions as the exposure conditions, (i.e. wavelength, numerical aperture, sigma, and illumination aperture type) and by comparing multiple dies to find errors in the line width. Surface defects are detected all over the reticle. The detection of surface defects is performed by acquiring transmission and dark-field reflection images of the reticle and using the combined information to detect particles, and other surface defects.
196 Citations
32 Claims
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1. A method for inspecting a multiple die reticle that is used with an optical exposure system under a set of exposure conditions, said multiple die reticle including at least a first die and a second die, said method comprising:
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acquiring a plurality of aerial images of said reticle using a transmitted light, said plurality of aerial images being acquired within a process window of said exposure system and using said set of exposure conditions;
said plurality of aerial images including a first plurality of aerial images of said first die and a second plurality of aerial images of said second die; and
comparing said first plurality of aerial images of said first die and said second plurality of aerial images of said second die to detect variations in line width in said first die. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
a first aerial image of said first plurality of aerial images of said first die is in focus;
a second aerial image of said first plurality of aerial images of said first die is out of focus in a positive direction; and
a third aerial image of said first plurality of aerial images of said first die is out of focus in a negative direction.
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8. The method of claim 7, wherein:
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a first aerial image of said second plurality of aerial images of said second die is in focus;
a second aerial image of said second plurality of aerial images of said second die is out of focus in a positive direction; and
a third aerial image of said second plurality of aerial images of said second die is out of focus in a negative direction.
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9. The method of claim 1, further comprising:
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acquiring an image of said reticle using a reflected light; and
using said acquired image of said reticle and said plurality of aerial images of said reticle to detect defects in said reticle.
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10. The method of claim 9, wherein said reflected light is produced by illuminating said reticle using a dark field illumination system.
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11. The method of claim 1, further comprising displaying results of said comparison in a graphic form.
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12. The method of claim 1, further comprising using results of said comparison to produce a map of said variations in said line width of said first die.
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13. The method of claim 1, wherein said transmitted light is provided using a pulsating light source.
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14. The method of claim 13, wherein said pulsating light source is a pulsating laser.
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15. The method of claim 9, wherein said reflected light is provided using a pulsating light source.
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16. The method of claim 15, wherein said pulsating light source is a pulsating laser.
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17. The method of claim 1, wherein said acquiring said plurality of aerial images comprises placing said reticle on a stage and moving said stage in a continuous manner.
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18. The method of claim 13, wherein said acquiring said plurality of aerial images comprises placing said reticle on a stage and moving said stage in a continuous manner.
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19. The method of claim 15, wherein said acquiring said plurality of aerial images comprises placing said reticle on a stage and moving said stage in a continuous manner.
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20. A method for inspecting a reticle that is used with an optical exposure system under a set of exposure conditions, said method comprising:
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acquiring a plurality of aerial images of said reticle using a transmitted light, said plurality of aerial images being acquired within a process window of said exposure system and using said set of exposure conditions;
acquiring an image of said reticle using a reflected light; and
using said acquired image of said reticle and said plurality of aerial images of said reticle to detect defects in said reticle. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. A method for determining a process window for exposure of a multiple die reticle by an optical exposure system, said reticle to be exposed by said optical exposure system under a set of exposure conditions, said method comprising steps of:
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acquiring a plurality of aerial images of said reticle using a transmitted light under said set of exposure conditions; and
using said acquired aerial images to determine said process window of said optical exposure system. - View Dependent Claims (28, 29, 30, 31, 32)
a first image of said plurality of aerial images of said reticle is in focus;
a second image of said plurality of aerial images of said reticle is out of focus in a positive direction; and
a third image of said plurality of aerial images of said reticle is out of focus in a negative direction.
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29. The method of claim 27, wherein said plurality of aerial images of said reticle and said image of said reticle are acquired using a pulsating light source.
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30. The method of claim 29, wherein said pulsating light source is a pulsating laser.
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31. The method of claim 27, wherein said acquiring said plurality of aerial images comprises placing said reticle on a stage and moving said stage in a continuous manner.
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32. The method of claim 29, wherein said acquiring said plurality of aerial images comprises placing said reticle on a stage and moving said stage in a continuous manner.
Specification