Atomic Layer CVD for Continuously Shrinking Devices
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Atomic Layer CVD for Continuously Shrinking Devices Suvi Haukka, Kai-Erik Elers and Marko Tuominen ASM Microchemistry Ltd., Kutojantie 2B, P.O. Box 132, FIN-02631 Espoo, Finland ABSTRACT This paper will review the basics of the atomic layer chemical vapor deposition (ALCVD) thin film growth technique. The emphasis is on the ALCVD metal nitride growth and dual damascene barrier requirements. INTRODUCTION The shrinkage of IC device dimensions makes great demands on the thin film processing techniques. The processing technique should enable the growth of uniform ultra-thin films with atomic layer accuracy on large surface areas. Furthermore, the atomic layer accuracy should be realized in high aspect ratio vias and on irregular shaped surfaces to attain the best device performance. One possible technique to meet this challenge is atomic layer chemical vapor deposition (ALCVD).1,2,3 The ALCVD technique was developed in Finland in the early 1970´s by Dr. Tuomo Suntola. His very simple and revolutionary idea was to introduce the metal compound and nonmetal compound precursors sequentially to the surface and allow the reactive sites at the surface to control the film growth. This was contrary to conventional CVD where the precursors are introduced at the same time to the surface and the growth is controlled by the precursor flux intensity or the time of the growth. The basics of the ALCVD technique as well as the factors affecting the growth of ALCVD high-k gate dielectrics on differently treated silicon surfaces have previously been covered.4 Here the ALCVD growth basics are reviewed, emphasizing the metal nitride growth and dual damascene barrier requirements. DUAL DAMASCENE BARRIER REQUIREMENTS The barrier film should meet a great number of requirements (see Fig. 1). The film should have a low resistivity and almost no precursor residues should be incorporated into the film. Conformality is also crucial and the film should cover not only the bottom surface but also the side walls and bottom corners as well. Furthermore, in the dual damascene structure various surfaces are simultaneously present and the growth of the barrier film on these surfaces must equally be realized. The thickness of the barrier film will decrease with the decreasing feature size, which means that highly conformal ultra thin films (< 20 Å) will be needed in the future.
D6.4.1
• Resistivity < 500 µΩcm • Halide residues < 2.0 %
• Good growth and adhesion on low-k
• Thickness prof. < 2.0 % (8” wafer)
• Good growth and adhesion on the
• Step coverage ∼100 %
etch stopper
• The process rate > 30 Å/min
• Good growth and adhesion on SiO2
• CMP compatible
• Good growth and adhesion on Cu
• Thickness < 20 nm
• Good growth and adhesion on Al
• Deposition Temperature < 400 °C
Figure 1. Dual damascene barrier film requirements. ALCVD TECHNIQUE The basic principle of the ALCVD technique is simple: metal compounds and non-metal compounds are reacted alternatively with the growing surface with an inert gas purging step in between the reactions. Howe
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