Wafer handling system

Claim 1

A method of precisely positioning a semiconductor disc having a center and edge and bearing Θ indicia on a transport stage prior to optical exposure in a lithographic process comprising the steps of: rotating the water on a spinner about an axis normal to its major plane; detecting the displacement of the wafer edge relative to a fixed spatial location during said rotating step; determining, from the edge displacement, the displacement of the wafer center along orthogonal X and Y axes from the axis of rotation; detecting the Θ indicia during said rotating step; stopping rotation of the wafer with its Θ indicia substantially located in a predetermined angular position; calculating orthogonal X and Y axes offsets to compensate for wafer center displacement and remaining displacement of the Θ indicia; positioning the transport stage based on said calculating step along orthogonal X and Y axes to compensate for wafer center displacement and for the remaining displacement of the indicia from the predetermined angular position; and depositing the wafer from the spinner onto the transport stage whereby said wafer is accurately positioned thereon in X, Y and Θ.

Claim 2

A method of precisely positioning a semiconductor disc having a center and edge and bearing Θ indicia on a transport stage prior to optical exposure in a lithographic process comprising the steps of: rotating the water on a spinner about an axis normal to its major plane; detecting the displacement of the wafer edge relative to a fixed spatial location during said rotating step; determining, from the edge displacement, the displacement of the wafer center along orthogonal X and Y axes from the axis of rotation; detecting the Θ indicia during said rotating step; stopping rotation of the wafer with its Θ indicia substantially located in a predetermined angular position; calculating orthogonal X and Y axes offsets to compensate for wafer center displacement and remaining displacement of the Θ indicia; positioning the transport stage based on said calculating step along orthogonal X and Y axes to compensate for wafer center displacement and for the remaining displacement of the indicia from the predetermined angular position; and depositing the wafer from the spinner onto the transport stage whereby said wafer is accurately positioned thereon in X, Y and Θ.