In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2014-01, No. 36 ( 2014-04-01), p. 1359-1359
Abstract:
Atomically controlled processing has become indis-pensable for the fabrication of Si-based ultrasmall devices and heterodevices for ultralarge scale integration. Our concept of atomically controlled processing is based on atomic-order surface reaction control [1-3]. The final goal is the generalization of atomic-order surface reaction processes and the creation of new properties in Si-based ultimate small structures which will lead to nanometer scale Si devices as well as Si-based quantum devices. Introduction of N atomic layer at the interface between the high-k dielectric and the channel has been employed to suppress the interface trap formation [4] . Additionally, the insertion of N atomic layer within the channel may be beneficial for high mobility channel formation [5,3]. In this work, we describe atomic-order thermal nitridation of Si 1-x Ge x (100) (x=0 - 1) Si(100) in an NH 3 environment in a low temperature range of 300-650°C using an ultraclean low-pressure CVD system and furthermore the thermal stability of nitride surface are discussed. It has been found that silicon nitride films are formed even at 300-650°C on Si(100) [6]. At 500°C or higher, N initially increases and tends to saturate to a certain value (N atomic amount (n N ) of about 2.7 x 10 15 cm -2 ; 4 atomic layers). At 400°C or lower, on the H-terminated Si surface after wet cleaning, the n N increases and the Si-hydride coverage decreases with increasing NH 3 exposure time. The Si-hydride becomes hardly observable when n N reaches the surface Si atomic amount (6.8 x 10 14 cm -2 ). On the H-free Si surface after preheating in Ar at 650°C, n N increases up to 2 x 10 14 cm -2 ( Fig.1 ) with the appearance of the Si-hydride instantly after NH 3 exposure at 300 and 400°C, indicating that NH 3 molecules dissociatively are adsorbed on the Si dangling bonds. Further ultrathin nitridation is accompanied by a decrease of the Si-hydride coverage. It is found that n N is well described by Langmuir-type physical adsorption and reaction of NH 3 on the Si surface [3] based on a fitting assuming that the NH 3 adsorption equilibrium constant with flash heating is the same as that without flash heating [7] ( Fig.2 ). For 30 min exposure of NH 3 at partial pressure of 550 Pa and 400°C, Si 1-x Ge x (100) and Ge (100) are also nitrided at atomic level [8-9]. After Ar or H 2 heat treatment at 400-700 °C under 60 Pa, N atomic amount on the atomic-order nitrided Si (100) and Si 0.6 Ge 0.4 (100) is scarcely changed. On the atomic-order nitrided Ge (100), N atomic amount tends to decrease with increasing the heat-treatment temperature and even by H 2 purging at the cooling period after the nitridation. On the nitrided Si 0.5 Ge 0.5 (100), amount of the nitrided Si atoms increases for the higher heat-treatment temperature, although the amount of the nitrided Ge atoms decreases ( Fig.3 ). It is suggested that N atoms bound to Ge atoms tend to be transferred to Si atoms at temperatures above 400 °C. It is confirmed by angle-resolved XPS that preferential nitridation of Si atoms at surface over Ge atoms induces Ge segregation beneath the surface nitrided layer. Additionally, N atoms for the nitrided Si 0.3 Ge 0.7 (100) dominantly form a Si 3 N 4 structure which stably remains even during heat treatment in H 2 at 400 °C [10]. References [1] J. Murota et al., Jpn. J. Appl. Phys. , 33 , 2290 (1994). [2] B. Tillack et al., Thin Solid Films , 369 ,.189 (2000). [3] J. Murota et al, Jpn. J. Appl. Phys. , 45 , 6767 (2006). [4] J. Huang et al., Appl. Phys. Lett., 88 , 143506 (2006). [5] Y. Jeong et al., Mat. Sci. Semicond. Process., 8 , 121 (2005). [6] T. Watanabe et al., J. Electrochem. Soc. , 145 , 4252 (1998). [7] T. Watanabe et al., Jpn. J. Appl. Phys. , 38 , 515(1999). [8] N. Akiyama et al., Appl. Surf. Sci., 254 , 6021 (2008). [9] N. Akiyama et al., Thin Solid Films 517 , 219 (2008). [10] T. Kawashima et al. Thin Solid Films 520 , 3392 (2012).
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2014-01/36/1359
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2014
detail.hit.zdb_id:
2438749-6
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