Optimization of Ultrathin ALD Tantalum Nitride Films for Zero-Thickness Liner Applications
- PDF / 475,896 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 15 Downloads / 212 Views
Optimization of Ultrathin ALD Tantalum Nitride Films for Zero-Thickness Liner Applications Oscar van der Straten, Yu Zhu, Eric Eisenbraun, and Alain Kaloyeros University at Albany Institute for Materials and School of Nanosciences and Nanoengineering, Albany, NY 12203 ABSTRACT A metal-organic atomic layer deposition (ALD) tantalum nitride process has been demonstrated for zero-thickness liner applications in advanced copper metallization schemes. Utilizing a commercially available ALD reactor, this process employs a liquid tantalum source (tertbutylimido tris(diethylamido) tantalum—TBTDET) and ammonia as the reactants. Key functionality data addressing the self-limiting nature of ALD film growth with respect to key process parameters including processing temperature and the substrate surface exposures to TBTDET and ammonia have been obtained, leading to the establishment of an optimized ALD processing window. Highly conformal, continuous, and smooth growth over high aspect ratio structures is exhibited, and incubation periods appear to be relatively substrate independent. Preliminary thermal and electrical copper barrier performance testing of the deposited films indicates that they hold promise for use in emerging nanoscale interconnect applications. INTRODUCTION Progressively more demanding requirements for copper diffusion barriers/liners are being encountered for integration in advanced copper/low-k metallization schemes, driven by ever decreasing device feature sizes [1]. Physical vapor deposition (PVD) techniques, such as sputtering have been the process of choice for copper barrier processing. However, PVD-based processing may have limited applicability in the metallization schemes of sub-100 nm device generations, primarily owing to their inability to yield high conformality over high-aspect ratio topographies. One of the most promising chemical vapor deposition (CVD)-based techniques which may provide a viable solution to overcome these issues is atomic layer deposition (ALD), a processing method based on self-limiting surface reactions occurring between substrate surface and the growing film, thus ensuring monolayer thickness control and therefore enabling the growth of perfectly conformal, continuous, and atomically smooth films [2]. ALD differentiates itself from CVD by the method of source chemical supply: in ALD, precursor and reactant are introduced alternately, while in CVD the source chemicals are introduced simultaneously. In addition, while CVD may exploit the use of gas-phase reactions and kinetically driven surface reactions, these are explicitly avoided in ALD processing, where by design only the chemisorbed surface reactants are to react. Given a suitable processing temperature window (i.e. below the decomposition temperature of the employed sources), and a significant adsorption rate of the source chemicals under investigation, the resulting self-limiting coverage and surface reactions are the key parameters which determine the controllability over the film thickness and thus conformality and
Data Loading...
