Overlay measurement methods with firat based probe microscope

A method for determining alignment of layers in a semiconductor device comprising the actions of:

• providing a first layer having detectable surface and subsurface material properties:
• positioning a photoresist layer over said first layer, said photoresist layer having detectable surface and subsurface material properties;
• imaging said first layer and said photoresist layer with a dual tip probe device
• comparing the detectable material properties;
• and
• mapping an alignment of the compared detectable material properties,
• wherein the dual tip probe comprises:
• a detection surface;
• a force sensor attached to said detection surface, said force sensor comprising:
• a pair of flexible mechanical structures each disposed a first distance above the detection surface so as to form a gap between the flexible mechanical structure and the detection surface, wherein each flexible mechanical structure is configured to independently deflect upon exposure to an external force, thereby changing the first distance;
• a probe tip disposed on an outer surface of each flexible mechanical structure;
• an actuator coupled to each flexible mechanical structure configured to apply force to the flexible mechanical structure;
• and
• a detector configured to measure deflection of each said flexible mechanical structure.