Browse Prior Art Database

Narrow Kerf Overlay Test Site

IP.com Disclosure Number: IPCOM000089709D
Original Publication Date: 1977-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Ananthakrishnan, RB: AUTHOR [+2]

Abstract

Fig. 1 depicts a narrow kerf overlay target design. Shown in this figure are different levels of mask designs (Figs. 1A and 1B) proposed to construct one overlay test site, as shown in Fig. 1C. The construction of several overlay targets from masking level to masking level, is assumed.

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Narrow Kerf Overlay Test Site

Fig. 1 depicts a narrow kerf overlay target design. Shown in this figure are different levels of mask designs (Figs. 1A and 1B) proposed to construct one overlay test site, as shown in Fig. 1C. The construction of several overlay targets from masking level to masking level, is assumed.

Fig. 2 depicts a conventional overlay test site for use with the system of U. S. Patent 3,957,376 for width and overlay measurements (W & 0). This test site limits tool operations for narrow kerfs.

Fig. 2 shows the previous conventional width and overlay measurement test site design. The width and overlay measurement spot of diameter D is shown in the center of the left side of the "overlay test site" and in the extreme measurement positions (due to spot-to-target tool misregistration, X). While measuring the left side of the overlay target, note that the spot in its allowable extreme left position is not allowed to intercept any of the left adjacent chip product area in order to prevent other diffraction returns from product area geometries to interfere with the main diffraction return signal of the overlay left side line width shown under measurement. A space Y was provided in the kerf to prevent the foregoing signal interference. A total of four table movements is required to measure X(1), X(2), Y(1) and Y(2) and compute the X and Y overlay accuracy.

Fig. 3 depicts a narrow kerf overlay test site design. In this design, the width and overlay measurement spot for the system of U. S. Patent 3,957,376 may be placed in the corner of the top target to optically transmit simultaneously the X and Y diffraction patterns to each of the two X and Y axis measurement reticon arrays. Thus, line widths X(1)...