X-ray method for the measurement, characterization, and analysis of periodic structures
Periodic spatial patterns of x-ray illumination are used to gather information about periodic objects. The structured illumination may be created using the interaction of a coherent or partially coherent x-ray source with a beam splitting grating to create a Talbot interference pattern with periodic structure. The object having periodic structures to be measured is then placed into the structured illumination, and the ensemble of signals from the multiple illumination spots is analyzed to determine various properties of the object and its structures. Applications to x-ray absorption/transmission, small angle x-ray scattering, x-ray fluorescence, x-ray reflectance, and x-ray diffraction are all possible using the method of the invention.
1. A method for examining an object with periodic structures, comprising:
selecting an object with periodic structures for examination;
determining a volume in which a Talbot interference pattern will be formed,
said Talbot interference pattern to be formed using
a source of x-rays and
an x-ray beam splitting grating,
and to be matched in dimension and pitch
to the object with periodic structures to be examined;
placing the object having periodic structures into said volume;
establishing the Talbot interference pattern;
aligning the periodic structures of the object
with the anti-nodes of the Talbot interference pattern; and
detecting an x-ray signal resulting from the interaction
of the Talbot interference pattern
and the periodic structures of the object.
2. The method of claim 1 , in which
the x-ray signal is a signal arising from transmission of x-rays through the periodic structures.
3. The method of claim 1 , in which
the x-ray signal is a signal arising from small angle x-ray scattering.
4. The method of claim 1 , in which
the source of x-rays is a microfocus source.
5. The method of claim 1 , in which
the source of x-rays is an extended source used in conjunction
with an absorbing grating comprising periodic apertures.
6. The method of claim 1 , in which
the source of x-rays comprises:
a vacuum chamber;
an emitter for an electron beam; and
an x-ray target comprising:
a substrate comprising a first material and, embedded in the substrate,
at least a plurality of discrete structures comprising a second material selected
for its x-ray generating properties,
and in which said plurality of discrete structures
are arranged to form a periodic pattern of sub-sources.
7. The method of claim 6 , in which
the first selected material is selected from the group consisting of:
beryllium, diamond, graphite, silicon, boron nitride, silicon carbide, sapphire and diamond-like carbon; and
the second material is selected from the group consisting of:
iron, cobalt, nickel, copper, gallium, zinc, yttrium, zirconium, molybdenum, niobium, ruthenium, rhodium, palladium, silver, tin, iridium, tantalum, tungsten, indium, cesium, barium, gold, platinum, lead and combinations and alloys thereof.
8. The method of claim 1 , in which
the x-ray beam splitting grating comprises structures to introduce a phase-shift of approximately radians for a predetermined x-ray wavelength.
9. The method of claim 1 , in which
the x-ray beam splitting grating comprises structures to introduce a phase-shift of approximately π/2 radians for a predetermined x-ray wavelength.
10. The method of claim 1 , in which
the x-ray beam splitting grating comprises
an x-ray phase-shifting grating, in which
the period p 1 of the x-ray phase-shifting grating
is less than or equal to the lateral coherence length
of the x-rays from the x-ray source.
11. The method of claim 1 , in which
matching the Talbot interference pattern
to the object having periodic structures to be examined comprises
selecting the x-ray beam splitting grating so that the anti-nodes of the Talbot interference pattern have the same pitch to overlap the periodic structures of the object.
12. The method of claim 1 , in which
matching the Talbot interference pattern
to the object having periodic structures to be examined comprises
selecting the x-ray beam splitting grating so that the anti-nodes of the Talbot interference pattern have a pitch that is an integer multiple of the periodic structures of the object and will overlap a subset of the periodic structures of the object.
13. The method of claim 12 , in which
the object having periodic structures is selected from the group consisting of:
a semiconductor wafer, an integrated circuit, and
a packaging component for an integrated circuit; and
the x-ray signal provides information that leads to a determination of at least one of the properties of the periodic structures of the object selected from the group consisting of:
critical dimensions, sidewall angle, pitch, and linewidth roughness.