Wafer target design and method for determining centroid of wafer target
AssigneeKoninklijke Philips Electronics N.V.
InventorsBryan Hubbard, Pierre Leroux
Life of this patent
Estimating the term…
Abstract
A method for determining the centroid of a wafer target. In one embodiment, the method comprises a series of steps in a stepper, starting with the step of receiving a wafer, having a target set formed therein. Next, a signal is passed over the target set and over a material separating target shapes in the target set. Then a return signal is reflected, and received, from the surface of the target shapes and the material separating them. A location of at least one maxima point of the return signal is identified. Finally, a centroid is determined as the median of the locations of at least one maxima point.
Claims14
A method of determining a centroid of a target set in a wafer, said method comprising the steps of:
- a) receiving said wafer, said wafer having said target set formed therein, said target set including a plurality of target shapes separated by a material;
- b) passing a signal over said plurality of target shapes and over said material of said target set;
- c) receiving a return signal that is reflected from said plurality of target shapes and from said material separating said plurality of target shapes within said target set;
- d) identifying a location of each of at least one extrema of said return signal reflected from said material separating said plurality of target shapes within said target set;
- and
- e) determining said centroid of said target set from said at least one extrema of said return signal.
A method of determining a centroid of a target set in a wafer, said method comprising the steps of:
- receiving said wafer, said wafer having said target set formed therein, said target set including a plurality of target shapes separated by a material wherein said plurality of target shapes includes two rectangular target shapes;
- passing a signal over said plurality of target shapes and over said material of said target set;
- receiving a return signal that is reflected from said plurality of target shapes and from said material separating said plurality of target shapes within said target set;
- identifying a location of each of at least one extrema of said return signal reflected from said material separating said plurality of target shapes within said target set wherein only one maxima point is generated;
- and
- determining said centroid of said target set from said at least one extrema of said return signal.
A method of determining a centroid of a target set in a wafer, said method comprising the steps of:
- receiving said wafer, said wafer having said target set formed therein, said target set including a plurality of target shapes separated by a material wherein said plurality of target shapes includes four rectangular target shapes;
- passing a signal over said plurality of target shapes and over said material of said target set;
- receiving a return signal that is reflected from said plurality of target shapes and from said material separating said plurality of target shapes within said target set;
- identifying a location of each of at least one extrema of said return signal reflected from said material separating said plurality of target shapes within said target set wherein said at least one extrema are comprised of three maxima points, said three maxima points including two outer maxima points and a center maxima point;
- and
- determining said centroid of said target set from said at least one extreme of said return signal.
A stepper for aligning a wafer, said stepper comprising:
- a processor;
- and
- a computer readable memory, said computer readable memory coupled to said processor, said computer readable memory containing program instructions stored therein that when executed by said processor implement a method for determining a centroid of a target set in said wafer, said method comprising the steps of:
- a) receiving said wafer, said wafer having said target set formed therein, said target set including a plurality of target shapes separated by a material;
- b) passing a signal over said plurality of target shapes and over said material of said target set;
- c) receiving a return signal that is reflected from said plurality of target shapes and from said material separating said plurality of target shapes within said target set;
- d) identifying a location of each of at least one extrema of said return signal from said material separating said plurality of target shapes within said target set;
- and
- e) determining said centroid of said target set from said at least one extrema of said return signal.
Dependencies are inferred from the claim text.