Humidity-dependent stability of amorphous germanium nitrides fabricated by plasma nitridation

Abstract

We have investigated the stability of amorphous germanium nitride (Ge3N4) layers formed by plasma nitridation of Ge(100) surfaces using x-ray photoelectron spectroscopy and atomic force microscopy. We have found that humidity in the air accelerates the degradation of Ge3N4 layers and that under 80% humidity condition, most of the Ge–N bonds convert to Ge–O bonds, producing a uniform GeO2 layer, within 12h even at room temperature. After this conversion of nitrides to oxides, the surface roughness drastically increased by forming GeO2 islands on the surfaces. These findings indicate that although Ge3N4 layers have superior thermal stability compared to the GeO2 layers, Ge3N4 reacts readily with hydroxyl groups and it is therefore essential to take the best care of the moisture in the fabrication of Ge-based devices with Ge3N4 insulator or passivation layers.

Nanocomposite Al–Ge–N thin films and their mechanical and optical properties

“…the peaks are shifted to higher binding energies compared to the metallic reference states. 26,[37][38][39][40][65][66][67][68][69] The position of the N 1s peak also agrees with N-Al and N-Ge bonds. 26,37,66,69 The binding energy differences (which are independent of E B scale calibration) from N 1s to Al 2p (D ¼ 323.0-323.3 eV) and from N 1s to Ge 3d (D ¼ 365.0-365.4 eV) also agree with the span of literature values for AlN (D ¼ 322.7-323.8 eV) 66 and Ge 3 N 4 (D ¼ 365.1-365.7 eV), 26,37,69 respectively.…”

“…26,36 Ge 3 N 4 is chemically relatively inert, stable towards air and water at 100 C as well as boiling NaOH (aq) , and it is only slowly attacked by concentrated acids such as HCl (aq) , H 2 SO 4(aq) and H 3 PO 4(aq) , but dissolves rapidly in concentrated HF (aq) and HNO 3(aq) . 30,35,36 The thermal stability is limited, with decomposition in air being observed above temperatures of 650 C. 14 Germanium nitride thin films have mainly been synthesized through three routes: (1) nitridation of Ge substrates, 26,[37][38][39][40] which generally yields stoichiometric Ge 3 N 4 ; (2) different chemical vapor deposition methods, 27,36,41,42 producing stoichiometric material; or (3) by reactive sputtering, [43][44][45][46][47][48][49][50][51][52][53][54] using N 2 , NH 3 or N 2 H 4 as reactive gas, which generally produces GeN y with different degrees of N-deficiency. All sputter-deposited GeN y material has been found to be amorphous, and the optical bandgap as well as the refractive index and the resistivity have been found to vary with N content.…”

Electrical Characteristics of Ge-Based Metal-Insulator-Semiconductor Devices with Ge<SUB>3</SUB>N<SUB>4</SUB> Dielectrics Formed by Plasma Nitridation

“…Our plasma nitridation system, which can be operated under atmospheric pressure conditions, has a porous electrode for generating large-scale and high-density plasma. [10][11][12] The chamber pressure during plasma nitridation was kept to the order of 10 3 Pa, and the other treatment conditions were as follows: nitridation time of 30 min, RF power of 50 W, distance between the electrode and Ge substrate of 1 cm, and substrate temperature of 450 C. After post nitridation annealing (PNA) in N 2 ambient at 450 C for 10 min, Au gate electrode was deposited by vacuum evaporation through a shadow mask. Sample transfer between the processing apparatuses was carried out immediately after each process steps.…”

Germanium oxynitride gate dielectrics formed by plasma nitridation of ultrathin thermal oxides on Ge(100)

“…Recently, pure nitrides ͑Ge 3 N 4 ͒ formed by nitrogen plasma have shown to exhibit superior physical stability over GeO 2 . [11][12][13] Moreover, the use of nitrogen plasma treatment for gaining carbon-free Ge surfaces owing to selective C-N bond formation and subsequent desorption at low temperatures has been demonstrated. 14 Based on this research and recent findings on pure Ge oxides and nitrides, we believe that scaled GeON gate dielectrics fabricated using surface nitridation of ultrathin GeO 2 layers by plasma exposure is one of the most reasonable solutions for future Ge-MIS devices.…”

“…Plasma nitridation of the oxide surfaces was conducted using ultrahigh vacuum-based plasma equipment less than 1 ϫ 10 −7 Pa at a substrate temperature of 350 °C. 12,13 Physical characterization of ultrathin oxides and oxynitrides was performed using x-ray photoelectron spectroscopy ͑XPS͒ with a monochromated Al K␣ line. The nitrogen depth profile was also estimated by angle-resolved XPS analysis.…”