Claims
- 1. A method of precisely positioning a semiconductor disc having a center and edge and bearing .THETA. 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 .THETA. indicia during said rotating step;
- stopping rotation of the wafer with its .THETA. 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 .THETA. 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 .THETA..
- 2. The method of claim 1 wherein said wafer is rotated no more than one revolution.
- 3. The method of claim 1 including the additional step of removing said wafer from a storage casette prior to the rotating step.
Parent Case Info
This application is a division of application Ser. No. 07/351,741, filed 4/17/89, now, U.S. Pat. No. 4,973,217 which is a division of application Ser. No. 07/012,538 filed 2/9/87, now, U.S. Pat. No. 4,846,626.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0053703 |
Mar 1983 |
JPX |
Divisions (2)
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Number |
Date |
Country |
Parent |
351741 |
Apr 1989 |
|
Parent |
12538 |
Feb 1987 |
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