System and method of providing mask quality control
AssigneeNumerical Technologies, Inc.
InventorsLinard Karklin, Linyong Pang, Lynn Cai
Life of this patent
Estimating the term…
Abstract
A simulated wafer image of a physical mask and a defect-free reference image are used to generate a severity score for each defect, thereby giving a customer meaningful information to accurately assess the consequences of using a mask or repairing that mask. The defect severity score is calculated based on a number of factors relating to the changes in critical dimensions of the neighbor features to the defect. A common process window can also be used to provide objective information regarding defect printability. Certain other aspects of the mask relating to mask quality, such as line edge roughness and contact corner rounding, can also be quantified by using the simulated wafer image of the physical mask.
Claims44
A method for determining edge roughness of a feature in a mask, the method comprising:
- determining a centerline of the feature based on a representation of the mask;
- measuring a first length of a first rib extending from the centerline to one edge of the feature;
- measuring a second length of a second rib extending from the centerline to the one edge of the feature;
- and
- comparing the first and second lengths to determine the edge roughness.
A method of repairing a mask, the method comprising:
- determining an edge roughness of a feature on the mask, wherein if the edge roughness is outside a predetermined value, then using a lithography tool to repair the mask.
A method of repairing a wafer, the method comprising:
- determining an edge roughness of a feature on the wafer, wherein if the edge roughness is outside a predetermined value, then using a lithography tool to repair the wafer.
A method of determining corner rounding of a contact in a lithographic mask, the method comprising:
- determining a centerline of the contact in a first direction;
- providing a plurality of theoretical cuts through the contact in a second direction substantially perpendicular to the first direction, wherein each cut provides a rib extending from the centerline to an edge of the contact;
- and
- comparing at least two ribs to determine corner rounding, one rib being located near a corner of the contact and another rib not being located near the corner.
A method of determining the symmetry of a contact in a lithographic mask, the method comprising:
- determining a first centerline of the contact in a first direction;
- providing a plurality of theoretical cuts through the contact in a second direction substantially perpendicular to the first direction, wherein each cut provides a first critical dimension extending from a first edge of the contact to a second edge of the contact;
- determining a centerline of the contact in the second direction;
- providing a plurality of theoretical cuts through the contact in a first direction substantially perpendicular to the first direction, wherein each cut provides a second critical dimension extending from a third edge of the contact to a fourth edge of the contact;
- and
- comparing the first and second critical dimensions to determine the symmetry of the contact.
A method of repairing a mask, the method comprising:
- determining any corner rounding of a contact on the wafer, wherein if the edge roughness is outside a predetermined value, then using a lithography tool to repair the wafer.
An integrated circuit comprising:
- a plurality of features for performing a function;
- and
- at least one repaired feature, wherein the at least one repaired feature resulted from an automatic defect severity score.
A mask inspection system, the system comprising:
- means for generating a simulated wafer image of a feature on a mask;
- means for determining a centerline for the simulated wafer image based on a defect-free representation of the feature;
- and
- means for measuring an aspect of the simulated wafer image based on the centerline.
An inspection system for analyzing a feature on a mask, the system comprising:
- means for generating a simulated wafer image of the feature;
- means for determining a centerline for the simulated wafer image of the feature based on a defect-free representation of the feature;
- and
- means for determining whether the feature passes a predetermined standard.
A method of quantifying a quality of a feature on a mask, the method comprising:
- (a) determining a centerline of the feature;
- (b) measuring a first length of a first rib extending from the centerline to one edge of the feature;
- (c) measuring a second length of a second rib extending from the centerline to the one edge of the feature;
- (d) comparing the first and second lengths;
- (e) continuing steps (b), (c), and (d) for a plurality of times;
- and
- (f) calculating a score for the quality of the feature based on steps (a)-(e).
A physical mask comprising:
- at least one feature being modified based on analyzing a centerline of a simulated wafer image of the feature, the centerline determined by a defect-free representation of the feature;
- and
- at least one feature being unmodified based on analyzing the centerline.
Computer software for determining edge roughness of a feature in a mask, the software comprising:
- means for determining a centerline of the feature based on a representation of the mask;
- means for measuring a first length of a first rib extending from the centerline to one edge of the feature;
- means for measuring a second length of a second rib extending from the centerline to the one edge of the feature;
- and
- means for comparing the first and second lengths to determine the edge roughness.
Computer software for determining corner rounding of a contact in a lithographic mask, the software comprising:
- means for determining a centerline of the contact in a first direction;
- means for providing a plurality of theoretical cuts through the contact in a second direction substantially perpendicular to the first direction, wherein each cut provides a rib extending from the centerline to an edge of the contact;
- and
- means for comparing at least two ribs to determine corner rounding, one rib being located near a corner of the contact and another rib not being located near the corner.
Computer software for determining the symmetry of a contact in a lithographic mask, the software comprising:
- means for determining a first centerline of the contact in a first direction;
- means for providing a plurality of theoretical cuts through the contact in a second direction substantially perpendicular to the first direction, wherein each cut provides a first critical dimension extending from a first edge of the contact to a second edge of the contact;
- means for determining a centerline of the contact in the second direction;
- means for providing a plurality of theoretical cuts through the contact in a first direction substantially perpendicular to the first direction, wherein each cut provides a second critical dimension extending from a third edge of the contact to a fourth edge of the contact;
- and
- means for comparing the first and second critical dimensions to determine the symmetry of the contact.
Dependencies are inferred from the claim text.