ALD Grown Rare-Earth High-k Oxides on Ge: Lowering of the Interface Trap Density and EOT Scalability

Abstract

Y2O3 and L2O3/ZrO2 stacks have been examined in terms of their electrical properties in Ge capacitors. It is discussed that scaling of L2O3/ZrO2 stacks into the sub 1 nm EOT regime can be achieved either by using thin amorphous La2O3 capped by a thin ZrO2 layer or by stabilizing the tetragonal or cubic very high-k phase of ZrO2 induced by diffused La and Ge atoms during a PDA step. Y2O3 shows very good interfacial qualities in terms of a low interface trap density and hysteresis when an annealing in O2 atmosphere is applied. Fowler-Nordheim tunneling is identified as the primary leakage current mechanism at high gate bias whereas for the low bias regime leakage current is primary conducted by direct tunneling through the Y2O3 layer.

Fabrication and MOS interface properties of ALD AlYO3/GeO /Ge gate stacks with plasma post oxidation

“…The Y 2 O 3 and AlYO 3 film thickness was measured as a function of the ALD cycle by ellipsometry. The deposition rate of Y 2 O 3 is estimated to be 0.12 nm/cycle, which is close to the previously reported value, 0.15nm/cycle [12]. Also, the permittivity estimated from the accumulation capacitance is found to be around 13, which is close to the ideal permittivity value of 15 [12] and twice higher than that of Al 2 O 3 .…”

“…The deposition rate of Y 2 O 3 is estimated to be 0.12 nm/cycle, which is close to the previously reported value, 0.15nm/cycle [12]. Also, the permittivity estimated from the accumulation capacitance is found to be around 13, which is close to the ideal permittivity value of 15 [12] and twice higher than that of Al 2 O 3 . On the other hand, the deposition rate of AlYO 3 are estimated as 0.18 nm/unit cycle, where one unit cycle includes one supply cycle of Al(CH 2 ) 3 and one supply cycle of (CpMe) 3 Y.…”

Electrical Properties and Interfacial Issues of HfO2/Ge MIS Capacitors Characterized by the Thickness of La2O3 Interlayer

“…The contribution of the La 2 O 3 interfacial passivation layer to the amount of interface traps at the La 2 O 3 /Ge interface could be explained as follows: during the ALD process of La( i- PrCp) 3 and H 2 O precursors and the high temperature PDA process, La 2 O 3 is more likely to react with outdiffused Ge atoms and Ge oxides nearby the interface to form stable LaGeO x compound. The stable LaGeO x compound could effectively suppress Ge outdiffusion, and further inhibit the decomposition or desorption from GeO 2 to volatile GeO (following the reaction equation of GeO 2 + Ge → 2GeO), contributing to the reduction of structural defects and dangling bonds [31,32]. The D it value (2.71 × 10 12 eV −1 cm −2 ) of sample S4 achieved in our work is comparable with the results obtained in the reported literatures at La 2 O 3 /Ge interfaces of 3 × 10 12 [8] and 3.5 × 10 12 eV −1 cm −2 [25], indicating that a La 2 O 3 passivation layer with 15 ALD cycles (~1.3 nm) can effectively suppress the generation of interface states at high k dielectrics/Ge interfaces.…”

Impacts of the Oxygen Precursor on the Interfacial Properties of LaxAlyO Films Grown by Atomic Layer Deposition on Ge

“…Being a thermally stable germanate compound on the surface of Ge substrate, LaGeO x was reported to be of help in suppressing Ge out-diffusion and improving interface quality. However, among the germanium oxides, GeO is volatile and sublimes leaving behind a defective interface contained lots of defects and dangling bonds, which makes it known to have an adverse influence on the interfacial properties [11]. Additionally, it has been reported that at temperatures of up to 430 °C, GeO 2 becomes unstable, and will react with substrate Ge atoms generating volatile GeO, following the reaction of GeO 2 + Ge → 2GeO [7].…”

“…Recently, rare earth oxides have been considered as a promising passivation interlayer for high-k dielectric grown on Ge [9]. Furthermore, La-based dielectric materials have been shown to form a good passivation layer due to the formation of a stable La germanate compound on Ge substrate which could prevent the formation of volatile GeO [10,11]. Among various deposition methods for growing high-k dielectric films, atomic layer deposition (ALD) has been considered as one of the most promising technique to produce high-k dielectric films in high quality due to the outstanding characteristics for precise thickness and composition control, excellent uniformity and process compatibility to conventional CMOS process [12,13].…”