Indentation load relaxation experiments with indentation depth in the submicron range
- PDF / 683,146 Bytes
- 7 Pages / 593.28 x 841.68 pts Page_size
- 62 Downloads / 181 Views
I. INTRODUCTION
Load relaxation or stress relaxation experiments have been reported by a number of investigators in conjunction with their research on deformation mechanisms in bulk solids. For example, Gupta and Li performed stress relaxation experiments to obtain stress versus time data of bulk metals, which formed the experimental basis for their internal stress-based theory for plastic deformation in metals.1 Later, in their work on a state variable theory for nonelastic deformation in crystalline solids, Hart and his co-workers relied extensively on data produced from load relaxation experiments.2"4 Stress relaxation tests have also been performed for a variety of engineering applications.5'6 Thin metal or nonmetal films deposited on a substrate are materials systems commonly found in microelectronics. In such a configuration, the deformation properties of the thin film are often different from those of a bulk specimen or a free standing film. Recently it has been shown by continuous indentation hardness, wafer bending, and x-ray measurements that the flow strength of a thin metal film deposited on a hard substrate is significantly higher than a corresponding bulk specimen or a free-standing film.7"11 The wafer bending and x-ray experiments have also been used to monitor stress relaxation in the same thin film systems. Hannula and co-workers have reported the use of indentation load relaxation experiments to investigate the deformation properties of metal films deposited on hard substrates.12 The attention given to these thin film systems is motivated in part by technological interests.13 The indentation load relaxation experiment offers an advantage of being able to probe the deformation properties of a thin film as a function of indentation depth and location. The purpose of this paper is to report further development of the ILR technique, emphasizing applications involving submicron indentation depths. A brief review of the principles of the load re"'Current address: IBM Corporation, 1701 North Street, Endicott, New York 13760. 2100
http://journals.cambridge.org
J. Mater. Res., Vol. 5, No. 10, Oct 1990
Downloaded: 16 Mar 2015
laxation experiment will be made first. Special considerations required for the present ILR experiments will then be discussed. Typical ILR data will be presented and discussed in terms of deformation mechanisms involved. II. THE PRINCIPLES OF THE LOAD RELAXATION EXPERIMENT
Conventional load relaxation experiments on bulk specimens are typically conducted in screw-driven tensile testing machines. The test specimen is mounted between two crossheads; one of the crossheads can be moved at a constant displacement rate. This test configuration can be represented schematically by an elastic element and a plastic element in series [Fig. l(a)]. The machine deforms elastically under an applied load; the specimen deforms elastically and plastically. The elastic element in Fig. l(a), K, represents a combination
K
i
x(t)
T L(t) i
/ /
(a)
(b)
FIG. 1. Schematic representation of the se
Data Loading...
