Hafnium oxide gate dielectrics on sulfur-passivated germanium

Abstract

Sulfur passivation of Ge(100) is achieved using aqueous ammonium sulfide (NH4)2S(aq). The passivation layer is largely preserved after atomic layer deposition of the high-κ dielectric material HfO2 when sufficiently low growth temperatures (e.g., 220°C) are employed. Oxygen incorporation is moderate and results in an electrically passivating GeOS interface layer. The HfO2∕GeOS∕Ge gate stack exhibits lower fixed charge and interface state density than a more conventional HfO2∕GeON∕Ge gate stack fabricated via an ammonia gas treatment.

Effect of Ge surface termination on oxidation behavior

“…Particularly, it is reported that an S-terminated Ge surface is more stable than an H-or halogen-terminated surface, because of its higher bond energy [23]. Therefore, S-passivation on a Ge surface has been demonstrated in high-k dielectrics deposition [13], the fabrication of an epitaxial heterostructure [14], and metal deposition [15].…”

“…Up to the present, various terminations and passivations, such as H-termination [3,4,7], halogen-termination [3], alkyltermination [3], Ba-passivation [8], As-passivation [9], Si thin layer-passivation [10], thiol-passivation [11,12], and sulfurtermination [3,[13][14][15][16][17][18][19][20][21][22] have been proposed. Particularly, it is reported that an S-terminated Ge surface is more stable than an H-or halogen-terminated surface, because of its higher bond energy [23].…”

Atomic Layer Deposition of High-k Dielectric Layers on Ge and III-V MOS Channels

“…However, the interface state densities of such devices were much too high for device applications (2). In subsequent work, passivating interfacial layers between the Ge channel and the high-κ dielectric were developed, for example a thin (~0.6 nm) epitaxial Si passivation layer ( 3 , 4 ), germanium oxynitride ( 5 ), and Spassivation (6,7).…”

Processing of germanium for integrated circuits

“…They include approaches with various types of interfacial layers such as Si [40,41], GeO 2 [42][43][44][45], oxynitrides [46][47][48][49], and different high-k dielectric materials [50][51][52]. Novel processes have been investigated, i.e.…”