Differential dose and focus monitor
AssigneeInternational Business Machines Corporation
InventorsCHRISTOPHER P. AUSSCHNITT, Timothy A. Brunner
Life of this patent
Estimating the term…
Abstract
A dose and focus monitor structure includes at least one complementary set of unit dose monitors and at least one complementary set of unit focus monitors. Each complementary set of unit dose monitors generate edges on a photoresist layer such that the edges move in opposite directions as a function of a dose offset. Each complementary set of unit focus monitors generates edges on the photoresist layer such that the edges move in opposite directions as a function of a focus offset. The dose and focus monitor structure generates self-compensating differential measurements of the dose offset and the focus offset such that the dose offset measurement and the focus offset measurement are independent of each other.
Claims20
A reticle comprising a dose and focus monitor structure, said dose and focus monitor structure comprising:
- at least one pair of unit dose monitors configured to print a first pair of printed shapes on a photoresist layer, upon lithographic exposure and development of said photoresist layer, said first pair of first printed shapes moving in opposite directions from positions corresponding to a nominal dose by a first offset distance that is proportional to a dose offset from said nominal dose;
- and
- at least one pair of unit focus monitors configured to print a second pair of printed shapes on said photoresist layer, upon lithographic exposure and development of said photoresist layer, said second pair of second printed shapes moving in opposite directions from positions corresponding to a nominal focus by a second offset distance that is proportional to a focus offset from said nominal focus.
A method of monitoring a dose and focus of a lithographic process, said method comprising:
- lithographically exposing and developing a photoresist layer on a substrate employing a reticle, said reticle including a dose and focus monitor structure that comprises:
- at least one pair of dose monitors configured to print a first pair of edges on a photoresist layer, upon lithographic exposure and development of said photoresist layer, said first pair of edges moving in opposite directions from positions corresponding to a nominal dose by a first offset distance that is proportional to a dose offset from said nominal dose;
- and
- at least one pair of focus monitors configured to print a second pair of edges on said photoresist layer, upon lithographic exposure and development of said photoresist layer, said second pair of edges moving in opposite directions from positions corresponding to a nominal focus by a second offset distance that is proportional to a focus offset from said nominal focus;
- measuring said first offset distance and said second offset distance from patterns in said lithographically exposed and developed photoresist layer;
- and
- determining said dose offset and said focus offset from said first offset distance and said second offset distance.
Dependencies are inferred from the claim text.