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US 12,761,570 B2Granted
Multi-overlay stacked grating metrology target
AssigneeKLA Corporation
InventorsJordan Pio, Yuval Lubashevsky, Itay Gdor, Nickolai Isakovitch
Life of this patent
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Abstract
An overlay metrology target includes a multi-layer grating structure formed as an overlapping grating structure with different pitches on three or more layers of a sample. The three or more layers of the sample may include at least a first layer, a second layer, and a third layer, where the overlapping grating structure is periodic along at least one of the scan direction or a direction orthogonal to the scan direction. The multi-layer grating structure may include a first-layer grating on the first layer with a first pitch, a second-layer grating on the second layer with a second pitch, and a third-layer grating on the third layer with a third pitch.
Claims10
An overlay metrology system comprising:
- an illumination sub-system comprising:
- an illumination source configured to generate an illumination beam;
- and
- one or more illumination optics configured to direct the illumination beam to an overlay target on a sample as the sample is scanned relative to the illumination beam along a scan direction when implementing a metrology recipe, wherein the overlay target in accordance with the metrology recipe includes three cells, the three cells comprising a first cell having a first multi-layer grating structure formed as a first-layer grating on a first layer with a first pitch, a second-layer grating on a second layer with a second pitch, and a third-layer grating on a third layer with a third pitch, wherein the first pitch, the second pitch, and the third pitch are different from one another;
- a second cell having a second multi-layer grating structure formed as a first-layer grating on the first layer with the second pitch, a second-layer grating on the second layer with the first pitch, and a third-layer grating on the third layer with the third pitch;
- and a third cell having a third multi-layer grating structure formed as a first-layer grating on the first layer with the third pitch, a second-layer grating on the second layer with the second pitch, and a third-layer grating on the third layer with the first pitch, and wherein the overlapping grating structures are periodic along at least one of the scan direction or a direction orthogonal to the scan direction;
- a collection sub-system comprising:
- a first photodetector located in a pupil plane at a first location to capture overlapping diffraction orders from the multi-layer grating structures in the one or more cells when implementing the metrology recipe;
- and
- a second photodetector located in the pupil plane at a second location to capture overlapping diffraction orders from the multi-layer grating structures in the three cells when implementing the metrology recipe;
- and
- a controller communicatively coupled to the first photodetector and the second photodetector, the controller including one or more processors configured to execute program instructions causing the one or more processors to:
- receive time-varying interference signals from the first photodetector and the second photodetector associated with the multi-layer grating structures in the three cells as the overlay target is scanned in accordance with the metrology recipe;
- and
- determine an overlay error between one of the first layer, the second layer, or the third layer of the sample based on the time-varying interference signals.
12 more elements
An overlay metrology target comprising:
- a multi-layer grating structure formed as an overlapping grating structure, wherein the overlapping grating structure including three cells, the three cells comprising a first cell having a first multi-layer grating structure formed as a first-layer grating on a first layer with a first pitch, a second-layer grating on a second layer with a second pitch, and a third-layer grating on a third layer with a third pitch, wherein the first pitch, the second pitch, and the third pitch are different from one another;
- a second cell having a second multi-layer grating structure formed as a first-layer grating on the first layer with the second pitch, a second-layer grating on the second layer with the first pitch, and a third-layer grating on the third layer with the third pitch;
- and a third cell having a third multi-layer grating structure formed as a first-layer grating on the first layer with the third pitch, a second-layer grating on the second layer with the second pitch, and a third-layer grating on the third layer with the first pitch, and wherein the overlapping grating structures are periodic along at least one of a scan direction or a direction orthogonal to the scan direction.
A method comprising:
- receiving time-varying interference signals from first and second photodetectors associated with a multi-layer grating structure in one or more cells as an overlay target is scanned in accordance with a metrology recipe, wherein the overlay target in accordance with the metrology recipe includes three cells, the three cells comprising a first cell having a first multi-layer grating structure formed as a first-layer grating on a first layer with a first pitch, a second-layer grating on a second layer with a second pitch, and a third-layer grating on a third layer with a third pitch, wherein the first pitch, the second pitch, and the third pitch are different from one another;
- a second cell having a second multi-layer grating structure formed as a first-layer grating on the first layer with the second pitch, a second-layer grating on the second layer with the first pitch, and a third-layer grating on the third layer with the third pitch;
- and a third cell having a third multi-layer grating structure formed as a first-layer grating on the first layer with the third pitch, a second-layer grating on the second layer with the second pitch, and a third-layer grating on the third layer with the first pitch, and wherein the overlapping grating structures are periodic along at least one of a scan direction or a direction orthogonal to the scan direction;
- and
- determining an overlay error between one of the first layer, the second layer, or the third layer of a sample based on the time-varying interference signals.
2 more elements
Dependencies are inferred from the claim text.