Mechanical Properties of Au Films on Silicon Substrates

Abstract

This paper presents the results of recent studies of the effects of film thickness on the mechanical properties of electron-beam (e-beam) deposited Au films on silicon substrates. Following a brief description of film microstructure and surface topography, film mechanical properties (Young's modulus and hardness) are determined using nanoindentation techniques. The effects of stiff silicon substrates on the Young's modulus are analyzed within the framework established by King [6 8]. The effects of indentation size on film hardness are also explained within the context of strain gradient plasticity theories and substrate effects. The plasticity length scale parameters are shown to scale with film thickness. The amount of material pile up is also shown to increase with decreasing film thickness, for a given ratio of indentation depth to film thickness. The implications of the work are discussed for applications of Au films on silicon substrates.

Keywords:

• Au
• Hardness
• Mechanical property
• Microstructure
• Modulus
• Silicon
• Substrate
• Thin films

ACKNOWLEDGMENTS

This work was supported by the National Science Foundation (Grant No: DMR 0213706 and Grant No: DMR 0231418). Appreciation is extended to the Program Managers (Dr. Ulrich Strom and Dr. Carmen Huber) for their encouragement and support. The authors would like to thank Prof. Jeffrey Kysar and Mr. Yong Gan for providing help on EBSD facilities at Columbia University. The authors are also grateful to Ms. Zong Zong for assistance with nanoindentation techniques. Finally, one of the authors (DN) would like to thank the REU program coordinators Dr. Jay Benzinger, Ms. Soonoo Aria, and Mr. Don Schoorman for their assistance.

Notes

*Zong et al. [14] show the length scale for bulk gold single crystal is ∼1.12 µm.