Method of preparing an integrated circuit die for imaging
Integrated circuit dies are prepared for imaging by completely etching away all metal from the metal lines without removing barrier layers that underlie the metal lines. The metal vias may also be removed, especially if they are formed from the same metal as the metal lines, as in copper damascene circuits. This provides high contrast images that permits circuit layout extraction software to readily distinguish between metal lines and vias.
1. A method of imaging an integrated circuit die, comprising:
removing all material covering a metal layer of the integrated circuit die to expose the metal layer;
removing all metal from metal lines of the metal layer while preserving a barrier layer that underlies each metal line; and
acquiring tile images of the barrier layer within an area of interest of the integrated circuit die;
wherein removing all metal from the metal lines further comprises removing all metal from vias descending downwards from the metal layer while preserving a barrier layer that surrounds each of the vias.
2. The method as claimed in claim 1 wherein removing all material covering the metal layer comprises etching away a passivation layer or an interlayer dielectric material using a dry etching process.
3. The method as claimed in claim 1 wherein removing all material from the metal layer comprises etching away a passivation layer or an interlayer dielectric material using a wet etching process.
4. The method as claimed in claim 1 wherein removing all material covering the metal layer comprises removing a passivation layer or an interlayer dielectric material using a chemical or mechanical polishing process.
5. The method as claimed in claim 1 wherein removing all metal from the metal lines comprises etching away the metal lines using a wet or a dry etching process.
6. The method as claimed in claim 1 wherein acquiring tile images comprises acquiring the tile images using a scanning electron microscope.
7. The method as claimed in claim 1 further comprising stitching together the tile images to form an image mosaic of the exposed barrier layer.
8. The method as claimed in claim 7 further comprising vertically aligning image mosaics of a plurality of exposed layers to form a three-dimensional model of the integrated circuit.
9. The method as claimed in claim 8 further comprising extracting features of the integrated circuit to reconstruct a parametric representation based on the aligned mosaic images.
10. The method as claimed in claim 9 further comprising extracting circuit information from the parametric representation.
11. The method as claimed in claim 10 further comprising preparing a report based on the circuit information.
12. A method for extracting circuit information from an integrated circuit die, comprising:
for each metal layer of the integrated circuit die:
removing all material covering the metal layer;
removing metal lines from the metal layer to expose a barrier layer underlying each metal line;
placing the integrated circuit die on a precision stage and acquiring tile images of the barrier layer in an area of interest of the integrated circuit die; and
removing an interlayer dielectric material covering a polycrystalline silicon layer of the integrated circuit die, placing the integrated circuit die on the precision stage and acquiring tile images of the polycrystalline silicon layer;
wherein removing metal lines from the metal layer further comprises removing metal from vias descending downwards from the metal layer to expose a barrier layer surrounding each of the vias.