Browse Prior Art Database

Overlay Alignment Method

IP.com Disclosure Number: IPCOM000038053D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Maltabes, JG: AUTHOR [+2]

Abstract

By making both isotropic and anisotropic magnification adjustments to overlay projected image positions of six mask alignment marks on a corresponding six alignment marks in a previous mask level on each wafer, overlay error is improved significantly.

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Overlay Alignment Method

By making both isotropic and anisotropic magnification adjustments to overlay projected image positions of six mask alignment marks on a corresponding six alignment marks in a previous mask level on each wafer, overlay error is improved significantly.

Overlay alignment errors inherent in using two measurements on one send ahead wafer and making an isotropic magnification adjustment based on these measurements for the exposure of an entire wafer batch has limited increased device density.

By writing control codes for an existing projection alignment and exposure system, position of alignment marks at six points on each wafer are first found and compared to location of alignment marks at a corresponding six locations in the projected image of the mask to be exposed. Next, the system adjusts magnification both isotropically and anisotropically to obtain a best fit overlay (least average error) of all six mask alignment marks on the corresponding alignment marks on the wafer. When overlay is optimized, exposure is initiated.

Disclosed anonymously.

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