Overlay measurement apparatus
AssigneeAuros Technology, Inc.
InventorsHyeon Gi Shin, Bo Kyung Ryu, Jung Sun Ko, Jin Woo Park
Life of this patent
Estimating the term…
Abstract
An overlay measurement apparatus that can quickly measure an overlay error between layers with a large height difference is provided. The overlay measurement apparatus measures an error between a first overlay mark and a second overlay mark formed in a pair on different layers of a wafer. The overlay measurement apparatus includes an imaging system configured to acquire alignment images of a pair of first and second overlay marks at a plurality of focus positions, and a controller communicatively coupled to the imaging system. The overlay measurement apparatus can rapidly and accurately measure an overlay error between layers with a large height difference.
Claims14
An overlay measurement apparatus for measuring an error between a first overlay mark and a second overlay mark formed in a pair on different layers of a wafer, the apparatus comprising:
- an imaging system configured to acquire alignment images of the first overlay mark and the second overlay mark at a plurality of focus positions;
- and
- a controller communicatively coupled to the imaging system,
- wherein the imaging system comprises:
- a first light source configured to emit a first illumination light for acquiring the alignment images;
- a second light source configured to emit a second illumination light;
- an objective lens configured to condense the first illumination light and the second illumination light into a measurement area of the wafer, and collect first reflected light and second reflected light reflected from the measurement area of the wafer;
- a first detector configured to collect the first reflected light emitted from the first light source and reflected from the measurement area of the wafer to obtain the alignment images;
- a second detector configured to acquire a signal that varies depending on the focus position from the second reflected light emitted from the second light source and reflected in the measurement area of the wafer;
- and
- a first actuator configured to adjust a distance between the measurement area of the wafer and the objective lens to adjust the focus positions, and
- wherein the controller comprises a processor configured to execute instructions stored in a memory of the controller
- to perform:
- a) receiving alignment images obtained through the imaging system at a plurality of focus positions in a measurement area;
- b) determining a position of a measure focus on the basis of a change in a contrast value of the first overlay mark and a change in a contrast value of the second overlay mark of the alignment images;
- c) obtaining a reference signal value that is a signal value from the second detector at the position of the measure focus;
- and
- d) measuring an overlay error based on a measurement image that is an alignment image obtained at the position of the measure focus.
Dependencies are inferred from the claim text.