Methods and apparatus for optimization of inspection speed by generation of stage speed profile and selection of care areas for automated wafer inspection
Disclosed are apparatus and methods for the generation of a stage speed profile and/or the selection of care areas for automated wafer inspection. The stage speed profile generated corresponds to a fastest speed the inspection machine is able to inspect provided a set of care areas. The set of care areas selected correspond to specific regions on the wafer which are to be imaged in detail by the inspection machine. The apparatus and methods herein may also calculate speed of inspection and coverage (and possibly other characteristics of the inspection) for a quantity of cases, and select the best trade-off of coverage versus inspection time using a cost function. Other aspects, features, and embodiments of the invention are also disclosed.
1. An apparatus for inspecting scattered areas on a surface of a manufactured substrate, the apparatus comprising:
a source for generating a beam;
a lens system configured to focus the beam onto a surface of the substrate;
a detector configured to detect radiation emitted from the substrate as a result of the beam impinging onto the surface;
a stage configured to hold the substrate and controllably move the substrate under the beam;
a system controller that executes an inspection application and a recipe generator, wherein the inspection application controls the apparatus during inspection of the substrate, wherein the recipe generator includes a care area selection module which receives inspection characteristics, machine characteristics, and wafer characteristics, and uses said characteristics to select a set of care areas for use by the inspection application; and
a stage speed profile generation module of the inspection application, wherein the stage speed profile generation module divides care areas to be inspected into swaths to be scanned, generates a list of care area extents and gap extents, and divides the list of care area extents and gap extents into groups of care areas that have no gap extent in a first dimension greater than one width of a field of view of the apparatus in the first dimension.
2. The apparatus of claim 1 , wherein the care area selection module creates a plurality of candidate sets of care areas spanning a range of defect coverage percentages.
3. The apparatus of claim 2 , wherein the care area selection module selects the candidate set which results in a lowest value of a cost function.
4. The apparatus of claim 3 , wherein the cost function is higher when a calculated time needed to inspect the candidate set is longer and is higher when a defect coverage percentage is lower.
5. The apparatus of claim 1 , wherein the stage speed profile generation module finds a maximum stage speed for each said group of care areas, applies acceleration and deceleration rate limitations to the maximum stage speed to determine a rate-limited maximum stage speed for each said group of care areas, and generates a stage speed profile using the rate-limited maximum stage speeds for the groups of care areas.
6. A computer-implemented method comprising:
executing a recipe generator on a computer system coupled to an electron beam inspection apparatus;
receiving inspection characteristics, machine characteristics, and wafer characteristics by a care area selection module of the recipe generator;
selecting a set of care areas by the care area selection module using the inspection characteristics, machine characteristics, and wafer characteristics;
receiving the set of care areas by a stage speed profile generation module; and
generating a stage speed profile by the stage speed profile generation module using the set of care areas by dividing the care areas into swaths to be scanned, generating a list of care area extents and gap extents, and dividing the list of care area extents and gap extents into groups of care areas that have no gap extent in a first dimension greater than one width of a field of view in the first dimension.
7. The computer-implemented method of claim 6 , wherein selecting the set of care areas by the care area selection module comprises:
creating a plurality of candidate sets of care areas spanning a range of defect coverage percentages.
8. The computer-implemented method of claim 7 , wherein selecting the set of care areas by the care area selection module further comprises:
selecting the candidate set which results in a lowest value of a cost function.
9. The computer-implemented method of claim 8 , wherein the cost function is higher if a calculated time needed to inspect the candidate set is longer and is higher if a defect coverage percentage is lower.
10. The computer-implemented method of claim 6 , wherein generating the stage speed profile by the stage speed profile generation module further comprises:
applying acceleration and deceleration rate limitations to the maximum stage speed to determine a rate-limited maximum stage speed for each said group of care areas.
11. The computer-implemented method of claim 10 , wherein generating the stage speed profile by the stage speed profile generation module further comprises:
generating a stage speed profile using the rate-limited maximum stage speeds for the groups of care areas.
12. A computer-implemented method of generating a stage speed profile, the method comprising:
receiving a set of care areas;
dividing the care areas into swaths to be scanned;
generating a list of care area extents and gap extents;
dividing the list of care area extents and gap extents into groups of care areas that have no gap extent in a first dimension greater than one width of a field of view in the first dimension;
applying acceleration and deceleration rate limitations to the maximum stage speed to determine a rate-limited maximum stage speed for each said group of care areas; and
generating the stage speed profile using the rate-limited maximum stage speeds for the groups of care areas.