Epitaxial CoSi 2 formation using an oxynitride buffer layer
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Keunwoo Lee Semiconductor R&D Division, Samsung Electronics Company, Yongin, Gyeonggi-Do 445-701, Korea
Dongock Kim, Taeyong Park, Honggyu Kim, and Hyeongtag Jeona) Division of Materials Science and Engineering, Hanyang University, Seoul 133-791, Korea (Received 25 September 2008; accepted 19 May 2009)
We investigated the epitaxial growth of CoSi2 (100) on an Si (100) substrate using a modified oxide mediated epitaxy (OME) method to overcome the disadvantages of the OME method. These disadvantages are sensitivity of Co films to contamination by oxygen and the need for reiterating the film growth process to obtain thicker films. To solve these problems, nitrogen atoms were incorporated into chemically grown oxide (SiOx) by NH3 plasma treatment prior to the deposition of a Co film on the oxynitride buffer layer using the metal organic chemical vapor deposition (MOCVD) method. Subsequently, ex situ rapid thermal annealing was performed to grow Co-silicide at a temperature between 400 C and 700 C for 1 min. The results show that the diffusion of Co was effectively controlled by the oxynitride buffer layer without the formation of additional SiOx in between Co and Si. Our findings indicate that by using an oxynitride buffer layer, CoSi2 films can be grown epitaxially despite the fact that the initial Co film was exposed to oxygen.
I. INTRODUCTION
With the continuous scaling-down of advanced semiconductor device size, a silicide process has become essential to improve device and circuit performance. However, increasingly stricter requirements have been placed on metal-silicide properties and performance to reduce parasitic resistance and propagation delay.1–3 Among the many types of metal silicides, cobalt disilicide (CoSi2) has been widely investigated for the contact materials of complementary metal-oxide semiconductor devices due to its low resistivity (10–20 mOcm), good chemical stability, and high thermal stability.4–7 In particular, similarity in crystal structure and relatively close lattice mismatch (1.2%) between CoSi2 and Si allow epitaxial growth of CoSi2 with the properties of high thermal stability against agglomeration, film uniformity, absence of grain-boundary diffusion path, and compatibility with shallow junction formation.8–11 During the cobalt silicidation process, the initial reaction of Co and Si results in the formation of polycrystalline Co-rich phases such as Co2Si and CoSi, followed by the formation of a polycrystalline CoSi2 phase at higher temperatures. However, the epitaxial CoSi2 can be grown by the direct formation of CoSi2 without the fora)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0320 J. Mater. Res., Vol. 24, No. 8, Aug 2009
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mation of intermediate phases such as Co2Si and CoSi.12,13 Therefore, retardation of Co diffusion into Si by a buffer layer at high temperatures should enable the growth of an epitaxial CoSi2 layer on Si substrates without the formation of Co-rich pha
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