Surface Roughness Evolution in Amorphous Tantalum Oxide Films Deposited by Pulsed Reactive Sputtering
- PDF / 397,740 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 60 Downloads / 222 Views
W5.11.1
Surface Roughness Evolution in Amorphous Tantalum Oxide Films Deposited by Pulsed Reactive Sputtering Pushkar Jain, Jasbir S. Juneja, Tansel Karabacak, Eugene J. Rymaszewski and Toh –Ming Lu Center of Integrated Electronics and Electronics Manufacturing Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA Tel: 518-276-6032, Fax: 518-276-8761 ABSTRACT The growth front roughness of Ta2O5 amorphous films grown by pulsed plasma d.c. reactive sputtering has been investigated using atomic force microscopy. Film deposition during reactive sputter deposition is explained based on dynamic scaling hypothesis in which both time and space scaling are considered simultaneously. The interface width w increases as a power law with deposition time t, w ~ tβ, with β = 0.45 + 0.03. The lateral correlation length ξ grows as ξ ~ t1/z, with 1/z = 0.61 + 0.07. The roughness exponent extracted from the slope of height-height correlation analysis is α = 0.79 + 0.04. The results are similar to that obtained by sputtering of elemental materials, and do not fit to any of the presently known growth models. Monte Carlo simulations were carried out based on a recently developed re-emission model, where incident flux distribution, shadowing, sticking coefficient, and surface diffusion mechanisms were accounted for in the deposition process. An important finding is that sticking coefficient must be less than unity to obtain the observed β value (~0.45). INTRODUCTION Tantalum oxide (Ta2O5) has been considered a promising high permittivity (high-k) dielectric material because of its potential applications as a dielectric in high-density dynamic random access memories (DRAMs) [1,2], as an alternative gate dielectric material for silicon dioxide [3], and as a thin film dielectric material in embedded capacitors for advanced packaging applications [4]. For all these applications, Ta2O5 thin films exhibiting low leakage current densities and high breakdown fields and capacitance densities are required for reliable electrical performance. The micro-roughness at metal-dielectric interfaces can significantly degrade the leakage and breakdown characteristics of thin film capacitors [5]. Higher effective electric field exists at the sharp and pointed regions at metal-dielectric interfaces. This results in higher leakage and premature electrical breakdown of the thin dielectric films at these locations. A physics based approach, to evaluate the interface roughness evolution, will help to correlate the interface roughness with the excessive leakage and lower breakdown characteristics of Ta2O5 films. In this study, films are deposited by reactive sputtering. It is a low temperature deposition technique and that makes it suitable for applications requiring low thermal budget. Surface roughness evolution during a reactive sputtering process has not been reported before. In this article, we extract the scaling exponents and suggest a re-emission model to describe the possible surface growth mechanisms during reactive sputter deposition. Different th
Data Loading...
