Study of Thermal Stability of HfO[sub x]N[sub y]∕Ge Capacitors Using Postdeposition Annealing and NH[sub 3] Plasma Pretreatment

Abstract

We studied the thermal stability of the as-deposited HfO x N y thin films on the Ge substrate by employing rapid thermal annealing. After undergoing high-temperature processing, we observed several interesting physical and electrical features presented in the HfO x N y /Ge system, including a large Ge out-diffusion ͑Ͼ15 atom %͒ into high-k films, positive shift of the flatband voltage, severe charge trapping, and increased leakage current. These phenomena are closely related to the existence of GeO x defective layer and the degree of resultant GeO volatilization. We abated these undesirable effects, especially for reducing the amount of Ge incorporation ͑Ͻ5 atom %͒ and the substoichiometric oxide at dielectric-substrate interface, through performing NH 3 plasma pretreatment on the Ge surface. These improvements can be interpreted in terms of a surface nitridation process that enhanced the thermal stability of the high-k/Ge interface. In addition, we measured that the conductance loss in inversion was still high and it revealed independence with respect to gate bias, reflecting the fact that the minority carriers in Ge can rapidly respond either through a diffusion mechanism or through midgap trap states residing in Ge bulk substrates.

Impact of germanium related defects on electrical performance of hafnium oxide

“…It has been experimentally observed that the outdiffusion 5 of Ge in channel will cause the degradation of gate dielectrics such as positive flatband voltage shift, 6-9 gate leakage current, [8][9][10] and hysteresis 8 enlargement. However, the mechanism for the degradation of Ge contaminated highk dielectrics is not clear yet.…”

“…Let us consider the Ge contaminated HfO 2 with n-type substrate and low work function metal gate ͑TaN, most well studied 6,7,9 ͒. According to the secondary ion mass spectroscopy analysis reported in previous publication, 5,8 Ge tends to pileup at the two interfaces of MOS capacitor ͑U shape͒. The ECP at the top interface ͑metal/oxide͒ is determined by the work function of the metal gate.…”

Interfacial, Electrical, and Band Alignment Characteristics of HfO2/Ge Stacks with In Situ-Formed SiO2 Interlayer by Plasma-Enhanced Atomic Layer Deposition

“…It has been demonstrated in many reported literatures that the GeO 2 degradation during the annealing will cause the positive V fb shift. The desorption process of Ge-O is believed to generate additional negative charges [28, 29]. Therefore, it can also be concluded that GeO 2 decomposition is suppressed by Ge-O-Si interlayer from V fb shift.…”

Novel Sn-assisted nitridation of Ge/HfO2 interface and improved electrical properties of the MOS capacitor

“…The nitridation of Ge surfaces prior to high-k film deposition is one of the best-known solutions because it is effective in suppressing Ge diffusion in metal oxides and leads to improved performance of Ge-based devices. [4][5][6][7][8][9][10][11] Annealing in NH 3 ambient is widely used for Ge surface nitridation and the formation of the GeON interface layer. [6][7][8][9][10] However, these methods for introducing the nitrogen element always involve high-temperature treatment above 550 °C.…”