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Nondestructive Slope/Thickness Measurement for Semiconductor Topology

IP.com Disclosure Number: IPCOM000046180D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Finnes, SJ: AUTHOR [+2]

Abstract

Typically semiconductor samples are cleaved and subsequently viewed with a scanning electron microscope (SEM) for the purpose of determining the thickness and edge slope of a structure, such as a contact hole.

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Nondestructive Slope/Thickness Measurement for Semiconductor Topology

Typically semiconductor samples are cleaved and subsequently viewed with a scanning electron microscope (SEM) for the purpose of determining the thickness and edge slope of a structure, such as a contact hole.

This disclosure is based on the capability of the SEM stage to tilt the specimen by a known angle. By viewing the structure at two angles, a direct calculation yields both the slope and thickness. Figs. 1 and 2 depict a cross section of a structure with sloped walls. In Fig. 1, the sample is viewed at normal incidence, and the width of the projected slope segment is labeled as W1 . In Fig. 2, the sample has been tilted 0 degrees, and a new projected width W2 is noted. It can be shown that the slope angle of the structure is given by the equation:

(Image Omitted)

Once 0 is known, the sample thickness, t, is easily calculated by the relationship:

(Image Omitted)

A more powerful aspect of the concept is realized when we note that the degree of process control is such that the slope angles on opposite sides of the structure are identical. In such cases, only one observation is required at some viewing angle other than 90OE. This situation is shown in Fig. 3. The equation for 0 is given below.

(Image Omitted)

When d2 = 0, TAN 0 = Cot 0 which means 90 - 0 = 0 / -, - /.

The technique can be utilized on whole wafers and is therefore applicable to nondestructive schemes.

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