Pattern invariant focusing of a charged particle beam
US7759642B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Apr 30, 2008 |
| Grant date | Jul 20, 2010 |
| Priority date | — |
| Expiry date | Jan 6, 2029 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J2237/221
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A method for focusing a scanning microscope, including scanning a primary charged particle beam across first sites of a reference die of a wafer, detecting a secondary beam emitted from the sites, and computing first focus scores for the sites based on the secondary beam. The method includes scanning the primary beam across second sites of a given die of the wafer while modulating a focal depth of the primary beam, the reference die and the given die having congruent layouts, the second sites corresponding vectorially in location with the first sites, and detecting the secondary beam emitted from the second sites in response to the primary beam. The method also includes computing second focus scores for the second sites based on the detected secondary beam emitted therefrom, and determining an exact focus of the primary beam for the second sites using the first and the second focus scores.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.