Fourier filtering mechanism for inspecting wafers
AssigneeKLA-Tencor Corporation
InventorsSteve Montesanto, Gershon Perelman, Rudolf Brunner
Life of this patent
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Abstract
The present invention resides in a Fourier filter to detect defects on semiconductor wafers. The present invention relates to a Fourier filter to detect defects on semiconductor wafers which is less susceptible to having the filter output affected by vibrations and which avoids the physical contact from conventional damping.
Claims21
A Fourier filtering mechanism for detecting defects in repetitive features on semiconductor wafers, comprising:
- an array of substantially coplanar adjustable blockages;
- a plurality of springs supporting the array of blockages, said array of blockages and said plurality of springs being fabricated by etching a sheet of conductive spring material;
- a plurality of positioning devices for stretching said plurality of springs and positioning said array of blockages;
- and
- a plurality of damping tabs fabricated from a conductive material, and positioned in proximity to an array of permanent magnets, for damping vibration of said springs.
A Fourier filtering mechanism for inspecting for defects in repetitive features in semiconductor structures, comprising:
- an array of substantially coplanar, mechanically adjustable blockages;
- a plurality of springs supporting the array of blockages;
- a plurality of damping tabs, attached to the plurality of springs, for damping vibration of the plurality of springs;
- the array of blockages, the plurality of springs and the plurality of damping tabs being fabricated from a conductive material which has been blackened;
- and
- an array of permanent magnets of alternating polarities, in proximity to, and for inducing eddy currents in, said plurality of damping tabs.
A method of using an array of blockages as a Fourier filtering mechanism for inspecting for defects in repetitive features in semiconductor devices, comprising the steps of:
- fabricating an array of blockages;
- illuminating an area of a semiconductor wafer with a means for producing substantially collimated light;
- positioning the array of blockages between the semiconductor wafer and an image sensor in a Fourier plane to block diffraction orders produced by the illuminating step;
- and
- positioning the semiconductor wafer relative to the position of the illuminating means so that different die patterns on the semiconductor wafer occupy the illuminated area.
A Fourier filtering mechanism for detecting defects in repetitive features on a semiconductor wafer, comprising:
- an array of substantially coplanar adjustable blockages;
- damping supports coupled to said adjustable blockages to minimize the effects of vibration;
- a source of substantially collimated light for illuminating an area of a semiconductor wafer;
- an image sensor for receiving said collimated light;
- and
- positioning devices for positioning said array of blockages and said damping supports in a Fourier plane between the semiconductor wafer and the image sensor to block diffraction orders produced by the collimated light impinging on said semiconductor wafer.
A Fourier filtering mechanism for inspecting for defects in repetitive features in semiconductor structures, comprising:
- an array of substantially coplanar adjustable mechanical blockages in a Fourier plane for use as a Fourier filter;
- and
- a parallelogram frame supporting the array of blockages, wherein the spacing of the blockages can be adjusted by altering the shape of the parallelogram.
A method of etching a conductive sheet having a first side and a second side to create a Fourier filtering mechanism for detecting defects in repetitive features on semiconductor wafers, comprising the steps of:
- masking out an array of blockages and a plurality of springs and damping tabs on a first side of a sheet of conductive material;
- masking out an array of blockages and a plurality of springs and damping tabs on a second side of the sheet of conductive material;
- etching out an array of blockages and a plurality of springs and damping tabs from the sheet of conductive material;
- and
- blackening at least part of the Fourier filtering mechanism after it is etched.
Dependencies are inferred from the claim text.