Scanning electron microscope (SEM) measurement method and apparatus
There are provided a scanning electron microscope (SEM) measurement method and/or apparatus that reduce critical dimension (CD) dispersion according to position correction of a measurement area in CD measurement in several SEM images of the same pattern. The SEM measurement method includes obtaining individual SEM images at a plurality of locations on a wafer via an SEM, generating a merged SEM image by aligning the individual SEMs and merging the individual SEM images, generating a merged measurement area in the merged SEM image, generating, in the individual SEM images, individual measurement areas corresponding to the merged measurement area, and measuring individual critical dimensions (CDs) in the individual measurement areas.
1 . A scanning electron microscope (SEM) measurement method comprising:
obtaining individual SEM images at a plurality of locations on a wafer via an SEM;
generating a merged SEM image by aligning the individual SEM images and by merging the individual SEM images;
generating a merged measurement area in the merged SEM image;
generating, in the individual SEM images, individual measurement areas corresponding to the merged measurement area; and
measuring individual critical dimensions (CDs) in the individual measurement areas.
2 . The SEM measurement method of claim 1 , wherein,
in the generating of the merged SEM image, motion vector values (Δi) by which the individual SEM images move are calculated (where, when the individual SEM images include N SEM images, i is an integer from 1 to N), and
in the generating of the individual measurement areas, the individual measurement areas are generated by applying negatives (−Δi) of the motion vector values (Δi) to the merged measurement area.
3 . The SEM measurement method of claim 1 , wherein alignment of the individual SEM images uses a cross-correlation coefficient.
4 . The SEM measurement method of claim 1 , wherein, in the generating of the merged measurement area, the merged measurement area is generated using a measurement area generation processor that automatically generates a measurement area.
5 . The SEM measurement method of claim 4 , wherein the measurement area generation processor automatically generates the measurement area by comparing a computer-aided design (CAD) image corresponding to the merged SEM image with the merged image.
6 . The SEM measurement method of claim 1 , further comprising:
correcting the merged measurement area in response to there being an error in a position of the merged measurement area,
wherein, in the generating of the individual measurement areas, the individual measurement areas are generated from the corrected merged measurement area.
7 . The SEM measurement method of claim 6 , wherein, in the correcting of the merged measurement area, the merged measurement area is corrected using a correction processor that automatically corrects a measurement area.
8 . The SEM measurement method of claim 1 , wherein
the merged measurement area or each of the individual measurement areas is defined as a two-dimensional measurement box (MB),
wherein, in response to pixels being allocated to a boundary portion of a pattern, the two-dimensional MB has a quadrangular shape defined to include a number of pixels in a width direction and to include, from among the number of pixels, outermost pixels on both sides in a length direction.
9 . The SEM measurement method of claim 8 , wherein, in the measuring of the individual CDs, each of the individual CDs is measured by averaging distances between both pixels corresponding to each of the number of pixels.
10 . The SEM measurement method of claim 1 , further comprising:
after the measuring of the individual CDs, predicting a representative CD by using the individual CDs.
11 . The SEM measurement method of claim 10 , wherein the representative CD is obtained by arithmetical averaging and/or weighted averaging of the individual CDs.
12 . A scanning electron microscope (SEM) measurement method comprising:
obtaining individual SEM images at a plurality of locations on a wafer via an SEM;
generating a merged SEM image by aligning and merging the individual SEM images;
generating a merged measurement area in the merged SEM image;
correcting the merged measurement area in response to there being an error in a position of the merged measurement area;
generating, in the individual SEM images, individual measurement areas corresponding to the merged measurement area;
measuring individual critical dimensions (CDs) in the individual measurement areas; and
predicting a representative CD by using the individual CDs.
13 . The SEM measurement method of claim 12 , wherein,
in the generating of the merged SEM image, motion vector values (Δi) by which the individual SEM images move are calculated (where, when the individual SEM images include N SEM images, i is an integer from 1 to N), and
in the generating of the individual measurement areas, the individual measurement areas are generated by applying negatives (−Δi) of the motion vector values (Δi) to the merged measurement area.
14 . The SEM measurement method of claim 12 , wherein
the alignment of the individual SEM images uses a cross-correlation coefficient, and
in the generating of the merged measurement area, the merged measurement area is generated using a measurement area generation processor that automatically generates a measurement area.
15 . The SEM measurement method of claim 12 , wherein
the merged measurement area or each of the individual measurement areas is defined as a two-dimensional measurement box (MB),
wherein, in response to pixels being allocated to a boundary portion of a pattern, the two-dimensional MB has a quadrangular shape defined to include a number of pixels in a width direction and to include, from among the number of pixels, outermost pixels on both sides in a length direction.
16 . The SEM measurement method of claim 12 , wherein the representative CD is obtained by arithmetical averaging and/or weighted averaging of the individual CDs.