System, method and apparatus for thin-film substrate signal separation using eddy current

A method for mapping a resistivity of a substrate comprising:

• determining a component of the eddy current sensor (ECS) signal attributable to a substrate relative to a first point on the surface of the substrate including:
• placing a substrate in a first position relative to an ECS at a first distance from the ECS, the substrate including a conductive film on a first surface of the substrate;
• detecting a first ECS signal with the substrate in the first position;
• inverting the substrate relative to the ECS such that the substrate is in a second position relative to the ECS at a second distance from the ECS, the second distance equal to the first distance less about a thickness of the substrate;
• detecting a second ECS signal with the substrate in the second position;
• determining a difference signal equal to a difference between a first signal level on a calibration graph for the ECS and the second signal level, the second signal level being shifted a distance about equal to the thickness of the substrate;
• and
• calculating a first substrate component of the first ECS signal equal to a product of the first distance and the difference signal, divided by the thickness of the substrate;
• determining a component of the eddy current sensor (ECS) signal attributable to a substrate relative to a second point on the surface of the substrate;
• calculating a first resistivity at the first point;
• calculating a second resistivity at the second point;
• and
• extrapolating a resistivity curve from the resistivity at the first point and the second point.

A system for determining a component of an eddy current sensor (ECS) signal attributable to a substrate comprising:

• an ECS oriented toward a substrate, the substrate in a first position relative to the ECS at a first distance from the ECS, the substrate including a conductive film on a first surface of the substrate;
• a substrate inverter capable of inverting the substrate relative to the ECS such that the substrate is in a second position relative to the ECS at a second distance from the ECS, the second distance equal to the first distance less about a thickness of the substrate
• a control system coupled to the ECS, the control system including:
• logic that detects a first ECS signal with the substrate in the first position;
• logic that detects a second ECS signal with the substrate in the second position;
• logic that determines a difference signal equal to a difference between a first signal level on a calibration graph for the ECS and the second signal level, the second signal level being shifted a distance about equal to the thickness of the substrate;
• and
• logic that calculates a first substrate component of the first ECS signal equal to a product of the first distance and the difference signal, divided by the thickness of the substrate.