The yield stress of polycrystalline thin films

In recent experiments it has been shown that the yield stress of polycrystalline thin films depends separately on the film thickness and the grain size. It was also shown that the grain size dependence varies as the reciprocal of the grain size. In this paper an analysis is presented which leads to these results and provides a more detailed understanding of the origins of the observed behavior.

Download Full-text

Mechanical Properties of Electroplated Copper Thin Films

MRS Proceedings ◽

10.1557/proc-594-63 ◽

1999 ◽

Vol 594 ◽

Cited By ~ 5

Author(s):

R. Spolenak ◽

C. A. Volkert ◽

K. Takahashi ◽

S. Fiorillo ◽

J. Miner ◽

...

Keyword(s):

Thin Films ◽

Mechanical Properties ◽

Grain Size ◽

Film Thickness ◽

Yield Stress ◽

Laser Scanning ◽

Focused Ion Beam ◽

Ion Beam ◽

Cu Films ◽

Electroplated Copper

AbstractIt is well known that the mechanical properties of thin films depend critically on film thickness However, the contributions from film thickness and grain size are difficult to separate, because they typically scale with each other. In one study by Venkatraman and Bravman, Al films, which were thinned using anodic oxidation to reduce film thickness without changing grain size, showed a clear increase in yield stress with decreasing film thickness.We have performed a similar study on both electroplated and sputtered Cu films by using chemical-mechanical polishing (CMP) to reduce the film thickness without changing the grain size. Stress-temperature curves were measured for both the electroplated and sputtered Cu films with thicknesses between 0.1 and 1.8 microns using a laser scanning wafer curvature technique. The yield stress at room temperature was found to increase with decreasing film thickness for both sets of samples. The sputtered films, however, showed higher yield stresses in comparison to the electroplated films. Most of these differences can be attributed to the different microstructures of the films, which were determined by focused ion beam (FIB) microscopy and x-ray diffraction.

Download Full-text

The instability of polycrystalline thin films: Experiment and theory

Journal of Materials Research ◽

10.1557/jmr.1990.0151 ◽

1990 ◽

Vol 5 (1) ◽

pp. 151-160 ◽

Cited By ~ 192

Author(s):

K. T. Miller ◽

F. F. Lange ◽

D. B. Marshall

Keyword(s):

Thin Films ◽

Grain Size ◽

Film Thickness ◽

Grain Growth ◽

Spherical Surface ◽

Polycrystalline Film ◽

Yttrium Nitrate ◽

Zirconium Acetate ◽

Polycrystalline Thin Films ◽

Average Grain Size

Dense polycrystalline thin films of ZrO2 (3 and 8 mol % Y2O3) were produced by the pyrolysis of zirconium acetate precursor films, which were deposited on single crystal Al2O3 substrates by spin-coating aqueous solutions of zirconium acetate and yttrium nitrate. Dense films were heat treated to encourage grain growth. With grain growth, these films broke into islands of ZrO2 grains. Identical areas were examined after each heat treatment to determine the mechanism that causes the polycrystalline film to uncover the substrate. Two mechanisms were detailed: (a) for a composition which inhibited grain growth and produced a polycrystalline film with very small grains, the smallest grains would disappear to uncover the substrate, and (b) for a composition which did not inhibit grain boundary motion, larger grains grew by enveloping a smaller grain and then developed more spherical surface morphologies, uncovering the substrate at three grain junctions. In both cases, the breakup phenomenon occurred when the average grain size was larger than the film thickness. Thermodynamic calculations show that this breakup lowers the free energy of the system when the grain-size-to-film-thickness ratio exceeds a critical value. These calculations also predict the conditions needed for polycrystalline thin film stability.

Download Full-text

Persistent current relaxation in polycrystalline superconducting thin films

International Journal of Modern Physics B ◽

10.1142/s0217979214501525 ◽

2014 ◽

Vol 28 (22) ◽

pp. 1450152

Author(s):

L. V. Belevtsov

Keyword(s):

Thin Films ◽

Grain Size ◽

Film Thickness ◽

Relaxation Rate ◽

Persistent Current ◽

Superconducting Thin Films ◽

Material Parameters ◽

Polycrystalline Thin Films ◽

Current Relaxation

The relaxation rate of persistent current is studied theoretically in superconducting polycrystalline thin films. It is shown that varying the material parameters of grain anisotropy, grain size and film thickness does guide to a change of the current relaxation rate (CRR) mode. The point of degeneracy of CRR was obtained. The film-thickness dependent maxima are found in the behavior of CRR.

Download Full-text

Experimental Study on the Thickness-Dependent Hardness of SiO2 Thin Films Using Nanoindentation

Coatings ◽

10.3390/coatings11010023 ◽

2020 ◽

Vol 11 (1) ◽

pp. 23

Author(s):

Weiguang Zhang ◽

Jijun Li ◽

Yongming Xing ◽

Xiaomeng Nie ◽

Fengchao Lang ◽

...

Keyword(s):

Thin Film ◽

Thin Films ◽

Grain Size ◽

Integrated Circuits ◽

Film Thickness ◽

Depth Range ◽

Micro Electro Mechanical Systems ◽

Si Substrates ◽

Sio2 Thin Film ◽

Average Grain Size

SiO2 thin films are widely used in micro-electro-mechanical systems, integrated circuits and optical thin film devices. Tremendous efforts have been devoted to studying the preparation technology and optical properties of SiO2 thin films, but little attention has been paid to their mechanical properties. Herein, the surface morphology of the 500-nm-thick, 1000-nm-thick and 2000-nm-thick SiO2 thin films on the Si substrates was observed by atomic force microscopy. The hardnesses of the three SiO2 thin films with different thicknesses were investigated by nanoindentation technique, and the dependence of the hardness of the SiO2 thin film with its thickness was analyzed. The results showed that the average grain size of SiO2 thin film increased with increasing film thickness. For the three SiO2 thin films with different thicknesses, the same relative penetration depth range of ~0.4–0.5 existed, above which the intrinsic hardness without substrate influence can be determined. The average intrinsic hardness of the SiO2 thin film decreased with the increasing film thickness and average grain size, which showed the similar trend with the Hall-Petch type relationship.

Download Full-text

Effect of Grain Size and Film Thickness on the Thermoelectric Properties of Flexible Sb2Te3 Thin Films

Advances in Materials Science and Engineering ◽

10.1155/2019/6954918 ◽

2019 ◽

Vol 2019 ◽

pp. 1-7 ◽

Cited By ~ 12

Author(s):

Pornsiri Wanarattikan ◽

Piya Jitthammapirom ◽

Rachsak Sakdanuphab ◽

Aparporn Sakulkalavek

Keyword(s):

Thin Films ◽

Thermal Conductivity ◽

Electrical Conductivity ◽

Grain Size ◽

Film Thickness ◽

Seebeck Coefficient ◽

Thermoelectric Properties ◽

Flexible Substrate ◽

Rf Magnetron Sputtering ◽

Mean Free Path

In this work, stoichiometric Sb2Te3 thin films with various thicknesses were deposited on a flexible substrate using RF magnetron sputtering. The grain size and thickness effects on the thermoelectric properties, such as the Seebeck coefficient (S), electrical conductivity (σ), power factor (PF), and thermal conductivity (k), were investigated. The results show that the grain size was directly related to film thickness. As the film thickness increased, the grain size also increased. The Seebeck coefficient and electrical conductivity corresponded to the grain size of the films. The mean free path of carriers increases as the grain size increases, resulting in a decrease in the Seebeck coefficient and increase in electrical conductivity. Electrical conductivity strongly affects the temperature dependence of PF which results in the highest value of 7.5 × 10−4 W/m·K2 at 250°C for film thickness thicker than 1 µm. In the thermal conductivity mechanism, film thickness affects the dominance of phonons or carriers. For film thicknesses less than 1 µm, the behaviour of the phonons is dominant, while both are dominant for film thicknesses greater than 1 µm. Control of the grain size and film thickness is thus critical for controlling the performance of Sb2Te3 thin films.

Download Full-text