Method for inspecting substrate, substrate inspecting system and electron beam apparatus
The present invention relates to a substrate inspection apparatus for inspecting a pattern formed on a substrate by irradiating a charged particle beam onto the substrate. The substrate inspection apparatus comprises: an electron beam apparatus including a charged particle beam source for emitting a charged particle beam, a primary optical system for irradiating the charged particle beam onto the substrate, a secondary optical system into which a secondary charged particle beam is introduced, the secondary charged particle beam being emitted from the substrate by an irradiation of the charged particle beam, a detection system for detecting the secondary charged particle beam introduced into said secondary optical system and outputting as an electric signal, and a process control system for processing and evaluating the electric signal; a stage unit for holding the substrate and moving the substrate relatively to said electron beam apparatus; a working chamber capable of shielding at least an upper region of the stage unit form outside to control under desired atmosphere; and a substrate load-unload mechanism for transferring the substrate into or out of the stage.
1. A substrate inspection method comprising:
emitting a primary charged particle beam from a charged particle beam source, wherein said charged particle beam source is actuated in a space charge limited region, wherein a shot noise reduction factor is smaller than 1 and said charge particle beam source has a pointed cathode;
focusing said emitting charged particle beams into a fine beam;
irradiating and scanning said fine charged particle beam onto a substrate through a primary optical system;
introducing a secondary charged particle beam into a secondary charge particle beam detector, said secondary charged particle beam being emitted from said substrate by said irradiation of said primary charged particle beam;
detecting said secondary charged particle beam having been introduced into said secondary charge particle beam detector and converting said detected secondary charged particle beam into an electric signal; and
processing said electric signal to evaluate said substrate, wherein said shot noise reduction factor is defined by the following equation,
S/N=n 1/2 /(Γ*2 1/2 )
where, S/N is signal to noise ratio, Γ is shot noise reduction factor, and n is the number of detected secondary electrons per pixel.
2. A substrate inspection method according to claim 1 , wherein the primary charged particle beam emitted from said charged particle beam source is irradiated onto a multi aperture plate having a plurality of apertures, and a plurality of charged particle beams having passed through said plurality of apertures are irradiated onto a substrate surface.
3. A substrate inspection method according to claim 1 , further comprising:
detecting the secondary charged particle beam emitted from said substrate to obtain image data; and
re-arranging said obtained image data to generate image data of an inspection region on the substrate.
4. A substrate inspection method according to claim 1 , further comprising:
storing in advance reference image data with respect to the substrate to be evaluated; and
evaluating the substrate by comparing said image data generated by an image source with said stored reference image data.
5. A substrate inspection method according to claim 2 , further comprising:
obtaining respective sub-image data by detecting said secondary charged particle beam emitted from a plurality of beams of said substrate;
wherein said substrate is controlled so as continuously move in the Y-axis direction,
respective charged particle beams are driven to simultaneously scan in the X-axis direction such that a scanning pitch of a plurality of primary charged particle beams on said substrate are arranged with equal spacing therebetween.
6. A substrate inspection method according to claim 1 , wherein a lens condition or an axial alignment condition of said primary and said secondary optical systems corresponding to a pixel size for scanning and irradiating said substrate are stored.
7. A substrate inspection method, according to claim 1 , further comprising:
converting said electric signal into a pattern information; and
comparing said pattern information with a reference pattern.
8. A substrate inspection method according to claim 1 , further comprising:
converting said electric signal received from said detection section into binary information;
converting said binary information into a rectangular pattern information; and
comparing said rectangular information with a reference pattern.
9. A substrate inspection method according to claim 1 , further comprising:
storing a reference image corresponding to said image of said substrate;
reading out said stored reference image;
comparing said image of said substrate with said readout reference image and detecting portions differing between each of said images; and
classifying said different portions into such defects including at least short-circuit, disconnection, convex, chipping, pinhole and isolation.