Long working distance interference microscope
AssigneeSandia Corporation
InventorsMichael B. Sinclair, Maarten P. DeBoer, Norman F. Smith
Life of this patent
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Abstract
Disclosed is a long working distance interference microscope suitable for three-dimensional imaging and metrology of MEMS devices and test structures on a standard microelectronics probe station. The long working distance of 10-30 mm allows standard probes or probe cards to be used. This enables nanometer-scale 3-D height profiles of MEMS test structures to be acquired across an entire wafer. A well-matched pair of reference/sample objectives is not required, significantly reducing the cost of this microscope, as compared to a Linnik microinterferometer.
Claims28
A two-beam, full-field imaging interference microscope, comprising:
- a source of coherent light;
- a beamsplitter, optically aligned with the coherent light source;
- a sample objective, optically aligned with the beamsplitter along a sample arm and disposed directly in front of a sample, for imaging the surface of the sample, whose surface is located at a front focal plane of the sample objective;
- a reference mirror, optically aligned with the beamsplitter;
- a reference objective, optically aligned with the beamsplitter along a reference arm, and disposed in-between the beamsplitter and the reference mirror and disposed directly in front of the reference mirror, for imaging the surface of the reference mirror, whose surface is located at a front focal plane of the reference objective;
- image forming means, optically aligned with both the sample arm and the reference arm, and disposed on the opposite side of the beamsplitter from the sample objective, for forming at an image plane a combined real image of both the surface of the sample and the surface of the reference mirror, whereby said combined real image contains one or more interference fringes;
- and
- divergence matching means for matching the divergence of the reference and sample arms, comprising means for adjusting the position of the reference objective along the reference arm;
- whereby the distance, LR, between the beamsplitter and a back focal plane of the reference objective can be adjusted to be equal to the distance, LS, between the beamsplitter and a back focal plane of the sample objective;
- thereby producing straight interference fringes at the image plane when the divergence, LR, of the reference arm matches the divergence, LS, of the sample arm;
- wherein the reference objective is not optically matched to the sample objective.
The interference microscope of 8, wherein the means for simultaneously translating the axial position of the reference mirror and the reference objective comprises a single movable stage capable of translating its position along the optic axis of the reference arm, wherein both the reference mirror and the reference objective are mounted on the single movable stage.
The interference microscope of 15, wherein the optical means comprises a converging lens.
Dependencies are inferred from the claim text.