Browse Prior Art Database

Use of Marks Formed In Resist To Verify E-Beam To Optical Mark Placement

IP.com Disclosure Number: IPCOM000048599D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Bentley, WJ: AUTHOR [+5]

Abstract

This proposal allows wafers to be reworked if not within the E-beam exposure tool capture range.

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Use of Marks Formed In Resist To Verify E-Beam To Optical Mark Placement

This proposal allows wafers to be reworked if not within the E-beam exposure tool capture range.

In the past, wafers have been scrapped because of rotational errors which exceed the capture range of an E-beam exposure tool. The errors are introduced when optically exposed registration marks are not placed within the allowable tolerances of an E-beam exposure tool. The mark placement could only be checked after registration marks were formed (etching, lift-off, etc.) permanently on the wafer, thus making it almost impossible to rework them.

By using an E-beam exposure tool, a mark developed in resist can be registered in a very short period. Fig. 1 illustrates a mark cross-section. The resist may be hardened prior to scanning, if needed, for the etching step. 0nly a few chips need to be registered in order to verify the correct placement of the optical marks. If registration is successful, the wafer need not be recoated and the resist marks can be reused to etch permanent marks into the wafer surface. If registration fails due to rotation, translational errors, etc., the wafer can be stripped and reworked.

Figs. 2 and 3 show resulting signals obtained by scanning an electron beam over a resist mark. Fig. 2 illustrate a backscattered electron diode signal, and Fig. 3 represents the corresponding differentiated AGC (automatic gain control) signal. The signal is formed solely by contrast differe...