Browse Prior Art Database

Alignment of Patterns on Two Sides of the Same Plate

IP.com Disclosure Number: IPCOM000115850D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Smolinski, JG: AUTHOR

Abstract

A method is described for the accurate transfer of alignment marks from the front of a glass mask to the back of the same mask. Since the transfer is optical, the resulting alignment between two pattern planes on the front and back of the same glass plate is more accurate than can be achieved by two pattern planes on substrates that are mechanically separate.

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Alignment of Patterns on Two Sides of the Same Plate

      A method is described for the accurate transfer of alignment
marks from the front of a glass mask to the back of the same mask.
Since the transfer is optical, the resulting alignment between two
pattern planes on the front and back of the same glass plate is more
accurate than can be achieved by two pattern planes on substrates
that are mechanically separate.

      Fig. 1 represents the front and rear view of a mask with
alignment marks that fall outside of the unit cell area.  The master
(front) alignment pattern is to be replicated on the rear of the
mask, preserving the exact master image with the orientation shown.

      Fig. 2 represents edge views of the same mask shown in Fig. 1.
In Fig. 2A, the existing front chrome image has been given a
transparent protective coating.  In Fig. 2B, a negative resist
material has been added to the rear of the mask.  When the master
alignment marks are illuminated by an energy source such as a laser
with parallel rays, the master alignment image is projected precisely
on the resist where the image is retained after developing.  The
remaining resist is stripped away, and a uniform chrome layer is
deposited on the rear of the mask as shown in Fig. 2C.  Then the
resist that forms the alignment image is stripped to leave accurately
transferred alignment marks defined by chrome.

      The alignment marks that have been transferred to the rear of
the mask ca...