ICMCTF2003 Session B9: Emerging Technologies and Critical Issues in Vapor Deposition

There is a rapidly growing interrest to use films deposited by atomic layer deposition in semiconductor device manufacturing. In atomic layer deposition substrates are exposed alternatively to two or more highly reactive precursors pulses. Process conditions ensure that during each pulse a self-limiting surface reaction takes place that is forming one molecular layer on the surface.

Using atomic layer deposition, high quality hafnium oxide and zirconium oxide gate dielelectric films can be deposited at a temperature as low as 300°C using hafnium chloride (or zirconium chloride) and water as precursors. Due to the self-limiting nature of the surface reactions the thickness control of the films is simple (0.05 nm/cycle). With a properly selected ultrathin silicon oxide surface layer on silicon, film nucleaction is rapid and film closure takes place after less then 1 nm of deposition. Further it will be shown that during film deposition there is no subtantial oxidation of the underlying silicon which enables to make gate dielectrics with an electrical thickness below 1 nm. Leakage currents of the films are several orders of magnitudes lower than that of equivalent conventional silicon dioxide gate dielectrics.

Advanced mixed oxide layers like hafnium aluminate or hafnium silicate can be deposited through pulse sequences in which two different metal compound precursors are alternated. It is demonstrated that by adjusting the pulse sequence the composition and other physical properties of these mixed oxides can be varied and optimized. Finally, it will be shown that by atomic layer deposition films can be deposited very conformally even on extremely non-planar substrates. This is done by applying enough precursor dose to allow for full surface saturation every deposition cycle.

Pulsed electron beam generated plasmas exhibit temporally and spatially dependent distributions of ionized, neutral and radical species that are well-understood from Langmuir probe and mass spectrometer measurements [1, 2]. Under appropriate extrinsic conditions, the densities of desirable plasma species are large compared to those observed in conventional processing discharges. A variety of materials processing systems have been designed in an effort to explore the utility of these characteristics of beam generated plasmas for nitriding and thin film deposition applications. The nitriding experiments were performed exclusively in an electron beam generated plasma, while the deposition experiments were performed using beam generated plasmas with and without auxillary sputtering magnetrons. Experiments have been designed to understand the role of electron beam plasmas in surface modification processes. Additionally, the control of plasma chemistry observed in beam generated plasmas facilitates the development of process-structure-property relationships in materials systems. To assess and correlate the effects of intrinsic plasma characteristics on the structure and properties of materials, scanning electron microscopy, x-ray diffraction, atomic force microscopy, hardness tests, and other conventional materials characterization techniques were used.

[1] S. Walton et al., Phys. Rev. E, 65, 46412 (2002). [2] D. Leonhardt et al., J. Vac. Sci. Technol. A, 19, 1367 (2001.

^*This work supported by the Office of Naval Research