Signal processing method and signal processing apparatus
AssigneeToshiba Memory Corporation
InventorsMotoki Kadowaki, Osamu Nagano
Life of this patent
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Abstract
In accordance with an embodiment, a signal processing method includes scanning a pattern on a substrate with a charged particle beam, detecting secondary charged particles emitted from the substrate by using a detector, outputting a signal, and filtering the signal. The detector is separated or divided into a plurality of regions, and the secondary charged particles are detected separately in each region of the detector. Intensity of the filtering is defined in dependence on a function f(θ) of an angle θ between a reference axis and a direction along which the secondary charged particles enter a detector plane. The reference axis is an arbitrary direction in a plane parallel to a surface of the substrate.
Claims4
A signal processing apparatus comprising:
- a charged particle source configured to generate charged particles and irradiates a substrate with a charged particle beam;
- an energy filter configured to selectively allows secondary charged particle having arbitrary energy intensity in the secondary charged particles emitted from the substrate to pass therethrough, based on an angle θ formed between a reference axis and a direction along which the secondary charged particles enter a detector plane, the reference axis being an arbitrary direction within a plane parallel to a surface of the substrate;
- a detection unit which detects secondary charged particles having energy that is not greater than a predetermined threshold value among the secondary charged particles emitted in a state of being separated or divided in N regions from the substrate, where N is an even number of 4 or more, to output a signal regarding the detected secondary charged particles by each region;
- and
- a signal processing unit configured to change an intensity of the energy filter while irradiating the charged particle beam, to calculate a S/N ratio in the regions in regard to the signal obtained by each region based on a result of changing the intensity of the energy filter, and to calculate a position of a defect in a depth direction or a depth of a bottom surface of the pattern based on the calculated S/N ratio.
Dependencies are inferred from the claim text.