Browse Prior Art Database

Width and Overlay Test Site Design for Narrow Kerf Products

IP.com Disclosure Number: IPCOM000088865D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Ananthakrishnan, RB: AUTHOR [+3]

Abstract

Described herein, is a test site for use with systems, such as shown in Fig. 1 and described in U. S. Patent 3,957,376, for measuring and determining if line edges which define the boundaries at different levels on a semiconductor device are spaced from each other within a predetermined range. A test site for an overlay target was normally in the form of a square within a square, as in Fig. 2. Each leg of the overlay is measured independently and the overlay misalignment is computed.

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Width and Overlay Test Site Design for Narrow Kerf Products

Described herein, is a test site for use with systems, such as shown in Fig. 1 and described in U. S. Patent 3,957,376, for measuring and determining if line edges which define the boundaries at different levels on a semiconductor device are spaced from each other within a predetermined range. A test site for an overlay target was normally in the form of a square within a square, as in Fig. 2. Each leg of the overlay is measured independently and the overlay misalignment is computed.

Fig. 3 displays a kerf structure suitable for more narrow kerf products. A differentiated cosine transform will have extrema at frequencies corresponding to A mils, B mils, C Mu'' and D Mu'' (the patterns at the two levels being deliberately misaligned by 10 Mu'' to make a point). The frequencies corresponding to A mils and B mils are normally beyond the range of the system and will not appear in the spectrum. The extrema corresponding to C and D Mu'' will be of opposite polarity and will be easily distinguished. In case of perfect alignment, these extrema will cancel each other.

The technique will require only one measurement per orthogonal overlay as opposed to two before (Fig. 1).

In the interest of conserving real estate, two orthogonal patterns (Fig. 3) could be combined to yield the orthogonal overlay misalignments (Fig. 4).

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