Method and machine for examining wafers
Method and machine utilizes the real-time recipe to perform weak point inspection on a series of wafers during the fabrication of integrated circuits. Each real-time recipe essentially corresponds to a practical fabrication history of a wafer to be examined and/or the examination results of at least one examined wafer of same “lot”. Therefore, different wafers can be examined by using different recipes where each recipe corresponds to a specific condition of a wafer to be examined, even these wafers are received by a machine for examining at the same time.
1. A method of inspecting a wafer, comprising:
determining whether a map stored in a database represents the wafer;
determining a first inspecting plan according to a critical area to define an inspection area on the wafer when a first condition is satisfied that is based on similarity of the critical area to the map, otherwise determining a second inspecting plan, wherein the first inspecting plan covers only a defect inspection area indicated by the map;
examining the wafer with a high resolution imaging tool using the first inspecting plan or the second inspecting plan; and
identifying defects in the inspection area according to at least one image taken by said high resolution imaging tool.
2. The method of claim 1 , wherein the first inspecting plan is constructed by a smart review sampling filter.
3. The method of claim 1 , wherein the high resolution imaging tool contains a swing objective retarding immersion lens (SORIL) objective lens.
4. The method of claim 1 , wherein the defect is identified by a universal defect identification unit.
5. The method of claim 1 , wherein the map comprises at least one of the following: a possible defect location within a die or a device provided by a prediction of a numerical simulation; a verified result of a previous inspection output of other defect scanning tool; and a historical wafer map result collected from a previous wafer that experienced all fabrication processes.
6. The method of claim 1 , wherein the critical area comprises a possible defect location.
7. The method of claim 6 , wherein the possible defect location comprises a forerunner to defects.
8. The method of claim 1 , further comprising
determining the critical area based on a prediction of a numerical simulation.
9. The method of claim 1 , further comprising
determining the critical area based on a result of image processing.
10. The method of claim 1 , further comprising
determining the critical area based on analysis of signatures of the wafer.
11. The method of claim 10 , wherein the analysis uses a graphic database system (GDS) file.
12. The method of claim 1 , wherein the first inspecting plan is determined based on at least one of the following: product information identifying a feature based on a semiconductor fabrication process; and detecting parameters that instruct the high resolution imaging tool what to do in the inspection area.
13. The method of claim 1 , wherein the first inspecting plan comprises instructions configured to cause the high resolution imaging tool to examine the wafer only in the critical area instead of the whole wafer.
14. The method of claim 1 , further comprising
determining a first similarity between a wafer map representing the wafer and another wafer map stored in the database;
in response to the first similarity exceeding a threshold, setting a wafer map flag value to a first value, otherwise setting the wafer map flag value to a second value; and
constructing the first inspecting plan when the wafer map flag is the first value, otherwise constructing the second inspecting plan according to full wafer inspection.
15. An apparatus comprising:
a load/unload assembly configured to receive a lot including a wafer;
a memory storing a set of instructions; and
a processor configured to execute the set of instructions to cause the apparatus to:
determine whether a map stored in a database represents the wafer;
construct a first inspecting plan for inspecting the wafer according to a critical area to define an inspection area on the wafer when a first condition is satisfied that is based on similarity of the critical area to the map, otherwise determining a second inspecting plan, wherein the first inspecting plan covers only a defect inspection area indicated by the map;
acquire at least one image of the wafer with a high resolution imaging tool using the first inspecting plan or the second inspecting plan; and
identify defects in said inspection area according to the at least one image.
16. The apparatus of claim 15 , wherein the first inspecting plan is constructed by a smart review sampling filter.
17. The apparatus of claim 15 , wherein said high resolution imaging tool contains a swing objective retarding immersion lens (SORIL) objective lens.
18. The apparatus of claim 15 , wherein the defects are identified by a universal defect identification unit.
19. The apparatus of claim 15 , wherein the map comprises at least one of the following: a possible defect location within a die or a device provided by a prediction of a numerical simulation; a verified result of a previous inspection output of other defect scanning tool; and a historical wafer map result collected from a previous wafer that experienced all fabrication processes.
20. A non-transitory computer readable medium that stores a set of instructions that is executable by at least one processor of an apparatus to cause the apparatus to perform a method for inspecting a wafer, the method comprising:
determining whether a map stored in a database represents the wafer;
determining a first inspecting plan according to a critical area to define an inspection area on the wafer when a first condition is satisfied that is based on similarity of the critical area to the map, otherwise determining a second inspecting plan, wherein the first inspecting plan covers only a defect inspection area indicated by the map;
examining the wafer with a high resolution imaging tool using the first inspecting plan or the second inspecting plan; and
identifying defects in the inspection area according to at least one image taken by said high resolution imaging tool.