Browse Prior Art Database

Integral Measurement of Micron Lines on Wafers, Masks and Layers by Using Diffraction

IP.com Disclosure Number: IPCOM000048060D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 55K

Publishing Venue

IBM

Related People

Stein, H: AUTHOR [+2]

Abstract

This invention relates to a technique for measuring linewidths involving the detection of a diffracted light pattern from a periodic test grating. This technique is particularly useful for a sample that has a series of spaced parallel lines that are process dependent and which form a test grating 10 on a substrate 12, as shown in Fig. 1. In this example, the technique is used to determine the average width of the lines 14 in the test grating 10.

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 54% of the total text.

Page 1 of 3

Integral Measurement of Micron Lines on Wafers, Masks and Layers by Using Diffraction

This invention relates to a technique for measuring linewidths involving the detection of a diffracted light pattern from a periodic test grating. This technique is particularly useful for a sample that has a series of spaced parallel lines that are process dependent and which form a test grating 10 on a substrate 12, as shown in Fig. 1. In this example, the technique is used to determine the average width of the lines 14 in the test grating 10.

The essence of the technique is to measure the intensity modulation of the grating diffraction pattern 16 located at an observation plane a distance, Z, away from the grating. This intensity modulation is determined by the mean line width of the lines forming the test grating. The technique may be used in a reflection mode, as shown in Fig. 1, or in a transmission mode (not shown).

As shown in Figs. 1 and 2, a polarized light source, for example, a laser, is focused by lens 24 onto a test grating 10. Focusing is not required but allows the use of smaller test gratings.

The consequence is geometrical enlargement of the diffraction pattern spots. The grating periodicity may be known before hand or determined by measurements of the mean separation of the orders of the diffraction pattern.

As shown in Figs. 1 and 3, the line widths of the lines forming the test grating can be found by observation of the position of a zero 17 of the intensity modulated diffraction pattern. The location of the diffraction orders are determined by the mean grating spacing
(d) shown in Fig. 2. The intensity envelope modulation 18 is determined primarily by location of the first zero 17 measured from the center yields: Linewidth equals (mean grating line spacing) over

(order number of the zero)

Increased resolution is possible by observing higher order zeros and/or inference of the zero location to...