Printer Friendly

In situ stress measurements during electrodeposition of thin films studied.

Thin films of various metals are used by the microelectronics community to produce, for example, solderable surface finishes, magnetic recording media, and copper wiring in printed circuit boards and integrated circuits. Such films tend to develop sizable mechanical stresses as they are deposited. Though not well understood, these stresses can result from the nucleation and growth process (e.g., lattice-mismatched epitaxial growth) or, in the case of the widely used technique of electrodeposition, from the use of solution additives and alloying elements needed to achieve desired deposition rates and mechanical properties. Often these stresses can approach or exceed the yield stress of the bulk material and can lead to loss of adhesion and the generation of bulk and surface defects. As feature sizes in microelectronic components continue to shrink, the stresses associated with the earliest stages of film growth raise serious concerns in the industry about device performance and reliability.

To address these concerns, NIST researchers have established a Class II (1 mW) HeNe optical bench dedicated to the in situ measurement of residual stress during electrodeposition using the wafer curvature method. The substrate is a 60 mm X3 mm X0.1 mm wafer of borosilicate glass onto which 250 nm of gold is evaporated. The curvature of the substrate is monitored during electrodeposition by reflecting the laser off of the glass/metal interface, through a series of mirrors and onto a position-sensitive detector. The average in-plane stress of a metal film electrodeposited onto the Au can be calculated from the deflection of the beam as a function of time. The apparatus can resolve surface stresses on the order of 0.3 N/m while the beam is in solution, thus allowing researchers to observe the stresses associated with the entire deposition process.

As a demonstration, NIST researchers have followed stress development in the first 50 nm of Cu deposited onto Au. This system is known to follow classical Stranski-Krastanov growth, where three-dimensional islands grow on top of one or more Cu monolayers. Researchers have quantified the surface stresses associated with the formation of the first Cu monolayer, as well as the formation and coalescence of discrete Cu nuclei. It is expected that measurements such as these will allow the researchers to determine the root cause of stress in electrodeposited thin films and to propose mitigation strategies.

CONTACT: Gery Stafford, (301) 975-6412; gery.stafford@nist.gov.
COPYRIGHT 2003 National Institute of Standards and Technology
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2003, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:General Developments
Publication:Journal of Research of the National Institute of Standards and Technology
Date:Nov 1, 2003
Words:396
Previous Article:NIST researchers use "frustrated" optical technique to measure formation of nanocoatings.
Next Article:One- and two-photon photoelectron spectroscopy used to study molecular electronics systems.
Topics:


Related Articles
WORKSHOP ON TEXTURE IN ELECTRONIC APPLICATIONS.
ELECTRODEPOSITED Pb-FREE SOLDER AND WHISKER PREVENTION.
RESONATING TORQUE MICROBALANCE DEVELOPED FOR IN SITU MEASUREMENTS OF FERROMAGNETIC FILMS WITH SUB-MONOLAYER SENSTIVITY.
NOVEL COMBINATORIAL METHODS FOR INORGANIC THIN FILMS.
Crystallographic texture in ceramics and metals.
Simultaneous biaxial stress and composition measurements made on [Al.sub.x][Ga.sub.l-x] As thin films. .
NIST researchers develop new microwave characterization tools for thin film circuits.
FSCT to offer a two-part virtual conference on Critical Pigment Volume Concentration.
The high resolution powder diffraction beam line at ESRF.
Effects of thickness and substrate on the mechanical properties of hard coatings.

Terms of use | Privacy policy | Copyright © 2021 Farlex, Inc. | Feedback | For webmasters |