Polishing apparatus
View Patent ↗The present invention relates to a polishing apparatus and a polishing method for polishing a workpiece, such as a wafer on which a pattern is formed, on a polishing pad, and more particularly, relates to a polishing apparatus and a polishing method for detecting a geometric element of a pattern, such as a pitch. The polishing apparatus includes: a polishing table ( 3 ) configured to support a polishing pad ( 2 ); a polishing head ( 1 ) configured to press a workpiece (W), having a pattern formed therein, against the polishing pad ( 2 ) and polish a surface of the workpiece (W), an imaging device ( 20 ) disposed in the polishing table ( 3 ) and configured to generate an image including at least the pattern of the workpiece (W), and an image analysis system ( 30 ) configured determining a geometric element of the pattern of the workpiece (W) based on the image.
1 . A polishing apparatus comprising:
a polishing table configured to support a polishing pad;
a polishing head configured to press a workpiece, having a pattern formed thereon, against the polishing pad and polish a surface of the workpiece;
an imaging device disposed in the polishing table and configured to generate an image including at least the pattern of the workpiece;
an image analysis system configured to determine a geometric element of the pattern of the workpiece based on the image; and
a lattice having a reference pattern formed therein, the reference pattern having a predefined shape and dimensions, wherein the lattice is disposed on the polishing table between the imaging device and the surface of the workpiece, wherein the imaging device captures an image of the pattern of the workpiece through the lattice, and wherein the image analysis system is configured to measure a line width of a moire pattern appearing on the image due to superimposition of the pattern of the workpiece and the reference pattern and calculate a pitch of the pattern of the workpiece from the line width of the moire pattern.
2 . The polishing apparatus according to claim 1 , wherein
the image analysis system is configured to:
obtain the image from the imaging device;
compare the moire pattern on the image with reference moire patterns on a plurality of reference images;
determine a reference image having a reference moire pattern that most matches the moire pattern on the image; and
determine a geometric element of a pattern associated with the determined reference image.
3 . The polishing apparatus according to claim 1 , further comprising:
a first prism and a second prism disposed in the polishing table; and
a light source facing the first prism,
wherein the imaging device faces the second prism,
the first prism is arranged so as to split light emitted by the light source into a first light that passes through the lattice to the workpiece and a second light that is reflected by the lattice, and
the second prism is arranged so as to superimpose the first light reflected by the workpiece and the second light reflected by the lattice, and to direct the first light and the second light, which are superimposed, to the imaging device.
4 . The polishing apparatus according to claim 1 , further comprising a beam splitter and a light source disposed in the polishing table,
wherein the light source and the lattice are arranged symmetrically with respect to the beam splitter,
the imaging device faces the beam splitter, and
the beam splitter is arranged so as to split light emitted by the light source into a first light reflected by the beam splitter and a second light passing through the beam splitter, direct the first light to the workpiece, and direct the second light to the lattice.
5 . The polishing apparatus according to claim 1 , wherein the reference pattern is a concentric pattern or a radial pattern.