Coordinated motion metrology with circular scanning

A coordinated motion bright field-dark field metrology device for circular image scanning, comprising:

• a metrology stage moveable in an X axis via an X axis motor assembly and moveable in a Y axis via a Y axis motor assembly;
• a metrology chuck positioned beneath said metrology stage, said chuck rotatable about a Z axis via C axis motor assembly, and moveable in a Z axis via a Z axis motor assembly;
• a modulator attached to said metrology stage, having a modulator wheel rotatable in an A axis by an A axis motor assembly and rotationally coordinated with said metrology chuck's C axis rotation;
• a scan light source attached to said metrology stage, passing a scan light beam through said rotatable modulator wheel and presenting a structured scan light beam onto a target on said metrology chuck;
• at least one alignment camera attached to said metrology stage;
• a dark field line scan camera attached to said metrology stage and with its shuttering coordinated to said C axis scan movement of said metrology stage and with said A axis rotation of said modulator wheel as said scan light source passes through said rotating modulator wheel when said modulator wheel and said metrology chuck reach a program speed;
• a bright field line scan camera attached to said metrology stage and with its shuttering coordinated to said C axis scan movement of said metrology stage and with said A axis rotation of said modulator wheel as said scan light source passes through said rotating modulator wheel when said modulator wheel and said metrology chuck are at a program speed;
• a motion controller connected to operate said X axis motor assembly, said Y axis motor assembly, said Z axis motor assembly, said C axis motor assembly, said A axis motor assembly, said BF scan camera, said DF scan camera, and said scan light source;
• a main computer providing instructions to said motion controller to coordinate the scan motion of said metrology chuck's rotation in said C axis, said modulator wheel's rotation in A axis and said bright field and dark field camera's shuttering, coincident with the powering on of said scan light source to perform a scan with a frame of reference for acquired scan images.

A method for a circular coordinated motion bright field-dark field circular image scanning metrology, comprising the steps of:

• Loading a wafer map of the Si wafer to be scanned into the main computer for use in the alignment of said Si wafer to a reference coordinate system;
• Robotically placing a Si wafer on a metrology chuck;
• Focusing all alignment cameras and bright field-dark field cameras attached to said metrology chuck;
• Algorithmically determining the precise location of the Si wafer on the chuck by referencing at least one of a positional indicia shown on an alignment camera to those on said wafer map;
• Algorithmically determining the Si wafer's X-Y offset from a center of the metrology chuck;
• Rotating said metrology chuck about the C axis to align the Si wafer with the wafer map and to position said Si wafer in a scan start reference position;
• Assigning this scan start reference position in the main computer as the X, Y, C, (0,0,0) positional coordinate;
• Positioning said metrology stage above said chuck at a start position for a circular scan;
• Rotate said metrology chuck to a pre-scan runup start position for a circular scan about said C axis;
• Rotate a modulator wheel to its pre-scan runup start position;
• Initiating a pre scan runup of said metrology chuck and said modulator wheel, powering on a light source simultaneously with the start of a bright field-dark field camera shuttering when the metrology chuck and the modulator wheel reach program speed to effect circular coordinated motion metrology;
• Performing a circular coordinated motion scan about the Si wafer with the BF and DF line scan cameras acquiring scan images and providing them to said main computer;
• Stopping said circular coordinated motion scan after it has gone 360 degrees around said Si wafer;
• Position said metrology stage in Y axis an offset distance approximately a width of said light source projected on said Si wafer and then move said metrology chuck in C axis to a pre-scan runup position for a new circular scan;
• Performing more circular coordinated motion metrology scans in a smaller, concentric circular scans until the wafer is fully scanned;
• Processing said acquired scan images, algorithmically linking said scan images to positional coordinates from a common frame of reference to develop a three dimensional topographical map of said Si wafer.

A method for spiral coordinated motion bright field-dark field circular image scanning metrology, comprising the steps of:

• Loading a wafer map of the Si wafer to be scanned into the main computer for use in the alignment of said Si wafer to a reference coordinate system;
• Robotically placing a Si wafer on a metrology chuck;
• Focusing all alignment cameras and bright field-dark field cameras attached to said metrology chuck;
• Algorithmically determining the precise location of the Si wafer on the chuck by referencing at least one of a positional indicia shown on an alignment camera to those on said wafer map;
• Algorithmically determining the Si wafer's X-Y offset from a center of the metrology chuck;
• Rotating said metrology chuck about the C axis to align the Si wafer with the wafer map and to position said Si wafer in a scan start reference position;
• Assigning this scan start reference position in the main computer as the X, Y, C, (0,0,0) positional coordinate;
• Positioning said metrology stage above said chuck at a Y axis pre-start runup position for a spiral scan;
• Rotate said metrology chuck to a pre-scan runup start position for a spiral scan about said C axis;
• Rotate a modulator wheel to its pre-scan runup start position;
• Initiating a pre scan runup of said metrology stage in Y axis, a pre-scan runup of said metrology chuck in C axis, and a pre-scan runup of said modulator wheel in A axis, powering on a light source simultaneously with the start of a bright field-dark field camera shuttering when the metrology chuck and the modulator wheel reach program speed to effect circular coordinated motion metrology;
• Performing a spiral coordinated motion scan about the Si wafer with the BF and DF line scan cameras acquiring scan images and providing them to said main computer until the entire Si wafer has been scanned;
• Processing said acquired scan images, algorithmically linking said scan images to positional coordinates from a common frame of reference to develop a three dimensional topographical map of said Si wafer.