Method and apparatus for the improvement of material/voltage contrast
AssigneeCredence Systems Corporation
InventorsErwan Le Roy, William B. Thompson
Life of this patent
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Abstract
A method and system for registering a CAD layout to a Focused Ion Beam image for through-the substrate probing, without using an optical image and without requiring biasing, includes an improved method of trench endpointing during the FIB milling operation with a low beam energy. The method further includes removal of Ga at the trench floor using XeF2, as well as the deposition of an insulating layer onto the trench floor.
Claims56
A method of establishing a non-transient voltage contrast between a first:
- doped region and a second doped region in a semiconductor wafer portion, said semiconductor wafer portion having a first surface and a second surface opposite said first surface;
- said wafer portion having a first semiconductor surface region of said second surface directly atop said first doped region, and having a second semiconductor surface region of said second surface directly atop said second doped region, said voltage contrast being observable on a charged particle beam image of said wafer portion, the method comprising the steps of:
- installing said wafer portion in a vacuum chamber in a charged particle beam apparatus;
- etching said first semiconductor surface region and said second semiconductor surface region with an etch chemistry for a first time period, for removing an implanted material-containing portion of said first semiconductor surface region and said second semiconductor surface region;
- following said first time period, depositing an insulator layer atop said etched first semiconductor surface region and said etched second semiconductor surface region;
- and
- forming an image of said first doped region and said second doped region from secondary electrons emitted from said first and said second doped region, said first doped region being unbiased electrically from said second doped region.
A method for endpointing the formation of a charged particle beam milled trench in a semiconductor wafer portion having a doped region therein and having a remaining region not coincident with said doped region, said doped region and said remaining region being unbiased electrically from one another, said doped region having a top surface, said trench having a bottom trench surface, comprising the steps of:
- milling said trench into said wafer portion at a first particle beam energy and a first particle beam current for a first milling time portion, said bottom trench surface after said first milling time portion being approximately 10 microns separated from said top surface of said doped region, a first portion of said trench being directly atop at least a portion of said doped region, a second portion of said trench being directly atop at least a portion of said remaining region;
- milling said trench into said wafer portion at a second particle beam energy and a second particle beam current for a second milling time portion while visually monitoring charged particle beam-induced secondary emission levels across said wafer portion, said second particle beam energy being substantially lower than said first particle beam energy;
- and
- halting said milling when a contrast in secondary emission levels between said doped region and said remaining region becomes noticeable.
Dependencies are inferred from the claim text.