In-die focus monitoring with binary mask
AssigneeAdvanced Micro Devices, Inc.
InventorRyoung-han Kim
Life of this patent
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Abstract
Focus monitoring for a photolithographic applications is provided by illuminating a photoresist layer with a light beam transmitted through a first binary mask to define a circuit pattern on an underlying substrate and then illuminating the photoresist layer with an unbalanced off-axis light beam transmitted through a second binary mask. The second mask contains a shifting feature configuration in one portion, while another portion blocks light transmission to the chip design area of the photoresist. After development of the photoresist layer, the pattern formed by illumination of the second mask can be compared with a predefined reference feature on the photoresist layer to determine whether a shift, if any, is within acceptable focus limits.
Claims21
A method for monitoring focus, the method comprising:
- a first step of illuminating a photoresist layer on a substrate with a light beam transmitted through a first mask to define a circuit pattern on the substrate;
- a second step of illuminating the photoresist layer with an unbalanced off-axis light beam transmitted through a second mask, the second mask containing a shifting feature configuration;
- developing the photoresist layer;
- comparing a pattern on the photoresist layer formed by the second illuminating step with a predefined reference feature on the photoresist layer;
- and
- determining whether the substrate position relative to the masks produces appropriate focus on the photoresist layer in response to the comparing step.
A focus monitoring apparatus comprising:
- a first binary mask comprising a pattern to be applied to a photoresist layer by exposure of the photoresist to a balance off-axis light illumination transmitted through the first binary mask;
- and
- a second binary mask comprising an image feature to be applied to the photoresist layer by exposure of the photoresist to an unbalanced off-axis light illumination transmitted through the second binary mask;
- wherein development of the photoresist after exposure to illumination through the first binary mask and the second binary mask provides an indication on the photoresist of a shift between an image feature of the pattern and a predetermined reference feature, to determine whether the photoresist position relative to the masks produces appropriate focus on the photoresist.
Dependencies are inferred from the claim text.