Variable image field curvature for object inspection
AssigneeKLA-Tencor Corporation
InventorPaul Horn
Life of this patent
Estimating the term…
Abstract
Field curvature of an optical system is modified based on topography of the surface of a wafer such that an image of each of the segments of the surface is in focus across the segment. The wafer may be non-planar. The optical system may be a multi-element lens system connected to a controller that modifies the field curvature by changing position of the lens elements. The wafer may be held by a chuck, such as an edge grip chuck. Multiple optical systems may be arranged across a dimension of the wafer.
Claims18
An inspection system comprising:
- an optical system for capturing images of segments of a surface of a wafer, the optical system having lens elements, wherein a position of the lens elements can be changed to modify field curvature, wherein the lens elements include:
- a first lens element having a positive refractive power, the first lens element comprising one or more lenses;
- a second lens element having a negative refractory power, the second lens element being adjacent to an imaging side of the first lens element, and the second lens element comprising one or more lenses;
- and
- a third lens element having a positive refractory power, the third lens element being adjacent to an imaging side of the second lens element, and the third lens element comprising one or more lenses;
- and
- a controller configured to:
- receive topography data of the surface of the wafer;
- and
- change a position of at least one of the lens elements based on the topography data of the surface of the wafer such that the field curvature of the optical system is modified and an image of each of the segments is in focus across the segment.
A non-transitory computer-readable storage medium, comprising one or more programs for executing the following steps on one or more computing devices:
- receiving topography data of at least a segment of a surface of a wafer;
- and
- modifying field curvature of an optical system based on the topography data such that an image of each of a plurality of segments of the surface is in focus across the segment wherein the optical system comprises a first lens element having a positive refractive power, a second lens element having a negative refractory power, and a third lens element having a positive refractory power, wherein the first lens element comprises one or more lenses, wherein the second lens element is adjacent to an imaging side of the first lens element, wherein the second lens element comprises one or more lenses, wherein the third lens element is adjacent to an imaging side of the second lens element, and wherein the third lens element comprises one or more lenses.
An inspection method comprising:
- receiving, at a controller, topography data of at least a segment of a surface of a wafer;
- modifying, based on the received topography data, field curvature of an optical system having a field of view corresponding to the segment, wherein the optical system comprises a first lens element having a positive refractive power, a second lens element having a negative refractory power, and a third lens element having a positive refractory power, wherein the first lens element comprises one or more lenses, wherein the second lens element is adjacent to an imaging side of the first lens element, wherein the second lens element comprises one or more lenses, wherein the third lens element is adjacent to an imaging side of the second lens element, and wherein the third lens element comprises one or more lenses;
- and
- capturing an image of the segment using the modified field curvature.
Dependencies are inferred from the claim text.