Method and apparatus for measuring a thickness of a layer of a wafer
First Claim
1. An apparatus for dynamically measuring a thickness of a layer of a wafer, comprising:
- an eddy current sensor having first and second sensor heads, said sensor heads positioned substantially opposite each other and defining a predetermined gap therebetween for passage by at least a portion of said wafer, said eddy current sensor configured to cause said first and second sensor heads to make measurements at a plurality of sampling locations on said wafer while said wafer is moving through said gap, said eddy current sensor including a circuit to generate an AC current to drive the first and second sensor heads at a frequency, and wherein the first and second sensor heads are connected in series to the circuit;
a robotic end effector configured to hold said wafer and move said wafer linearly through said gap while said measurements are made so that said measurements are made at said plurality of sampling locations along a line across said wafer; and
a controller connected to said eddy current sensor, said controller configured to determine said thickness of said layer of said wafer at said plurality of sampling locations from said measurements by said first and second sensor heads.
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Abstract
A method and apparatus are provided for measuring the thickness of a test object. The apparatus includes an eddy current sensor having first and second sensor heads. The sensor heads are positioned to have a predetermined gap therebetween for passage by at least a portion of the test object through the gap. The sensor heads make measurements at given sampling locations on the test object as the test object is moved through the gap. The apparatus also includes a position sensing mechanism to determine positions of the sampling locations on the test object. The apparatus also includes an evaluation circuit in communication with the eddy current sensor and to the position sensing mechanism for determining the thickness of the test object at the sampling locations.
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Citations
19 Claims
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1. An apparatus for dynamically measuring a thickness of a layer of a wafer, comprising:
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an eddy current sensor having first and second sensor heads, said sensor heads positioned substantially opposite each other and defining a predetermined gap therebetween for passage by at least a portion of said wafer, said eddy current sensor configured to cause said first and second sensor heads to make measurements at a plurality of sampling locations on said wafer while said wafer is moving through said gap, said eddy current sensor including a circuit to generate an AC current to drive the first and second sensor heads at a frequency, and wherein the first and second sensor heads are connected in series to the circuit; a robotic end effector configured to hold said wafer and move said wafer linearly through said gap while said measurements are made so that said measurements are made at said plurality of sampling locations along a line across said wafer; and a controller connected to said eddy current sensor, said controller configured to determine said thickness of said layer of said wafer at said plurality of sampling locations from said measurements by said first and second sensor heads. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of measuring thickness of a conductive layer of a wafer, comprising the steps of:
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moving the wafer linearly through a gap between first and second sensor heads of an eddy current sensor with a robotic end effector, the first and second sensor heads positioned substantially opposite each other to define the gap and connected in series to a circuit to generate an AC current to drive the first and second sensor heads at a frequency; making on-the-fly measurements of said conductive layer at a plurality of sampling locations along a line across said wafer using said first and second sensor heads while moving said wafer; and calculating in a controller the thickness of the conductive layer at said sampling locations from said measurements. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification