Browse Prior Art Database

Two Dimensional Crossed Coded Pattern for Automatic Alignment

IP.com Disclosure Number: IPCOM000086433D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Abraham, GA: AUTHOR [+3]

Abstract

The kerf area used for alignment patterns is reduced in half using a two-dimensional coded pattern. For automatic mask and wafer alignment, alignment on a plane with at least three degrees of freedom (X, Y and 0) of movement must be considered. Therefore, the target has to be designed along two independent axes (say X and Y) at two different locations, in order to establish the X, Y and 0 offset between the mask and the wafer. The signals from both axes should be independent. The simplest way to implement, is to put both X and Y patterns in two separate regions.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 98% of the total text.

Page 1 of 2

Two Dimensional Crossed Coded Pattern for Automatic Alignment

The kerf area used for alignment patterns is reduced in half using a two- dimensional coded pattern. For automatic mask and wafer alignment, alignment on a plane with at least three degrees of freedom (X, Y and 0) of movement must be considered. Therefore, the target has to be designed along two independent axes (say X and Y) at two different locations, in order to establish the X, Y and 0 offset between the mask and the wafer. The signals from both axes should be independent. The simplest way to implement, is to put both X and Y patterns in two separate regions.

On the mask, two sets of slits (one for the X pattern and one for the Y pattern) are required to scan over the conjugate wafer patterns sequentially (X then Y or Y then X) during the alignment. Therefore, for each local alignment site, the wafer area designated for the alignment will be at least twice as much as that used for a one axis alignment.

Two-dimensional cross-correlation alignment is implemented using less kerf area for alignment targets without sacrificing the alignment speed and accuracy, by putting the two-dimensional patterns (X and Y) in one unit cell as shown in the figure. In addition, by arranging the X and Y axes to be of angle Theta (Theta Not = N x 90 degrees), the X and Y alignment information can be picked up simultaneously with a single scan rather than scanning X and Y sequentially.

1

Page 2 of 2

2

[This page contains...