Browse Prior Art Database

Stress Measurement Device

IP.com Disclosure Number: IPCOM000047967D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Harper, JME: AUTHOR [+3]

Abstract

In the fabrication of integrated circuits, multilayer structures of metals and oxides are deposited onto semiconductor substrates. Stresses can occur in these structures due to lattice misfit and/or by differences in thermal expansion. These stresses cause the wafer to deform; for example, if a film of silicon nitride is deposited by chemical vapor deposition onto a flat silicon substrate, the substrate film combination will deform to the shape of a segment of a sphere, as shown in Fig. 1. This indicates that the film is under tension. The radius of curvature of the film/substrate is inversely proportional to the stress of the film.

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Stress Measurement Device

In the fabrication of integrated circuits, multilayer structures of metals and oxides are deposited onto semiconductor substrates. Stresses can occur in these structures due to lattice misfit and/or by differences in thermal expansion. These stresses cause the wafer to deform; for example, if a film of silicon nitride is deposited by chemical vapor deposition onto a flat silicon substrate, the substrate film combination will deform to the shape of a segment of a sphere, as shown in Fig. 1. This indicates that the film is under tension. The radius of curvature of the film/substrate is inversely proportional to the stress of the film. The stress in the film can be found by measuring the radius of curvature and applying the following relationship: Stress = C (ts/tf)1/R where C is a substrate constant, ts is the thickness of the substrate, tf is the thickness of the deposited film, and R is the radius of curvature. There is a simple, fast, and accurate device and method for measuring the stress in deposited films based on the above observations which will now be described. In this technique the film is deposited onto a miniature silicon cantilevered beam (Fig. 2) fabricated by a method described below. The end of the beam will deflect proportionally to the sign (compressive or tensile) and amount of stress caused by the film (Fig. 3). The deflection can be measured by a conventional optical microscope or comparator or by a scanning electron microscope. Using the relationship given above, the stress can be calculated. The beams can be very sensitive since they can be made with very large length-to-thickness ratios. Many of these...