Characterization of Gd[sub 2]O[sub 3] Films Deposited on Si(100) by Electron-Beam Evaporation

Abstract

Gadolinium oxide films were deposited on Si͑100͒ substrates from a rod-fed electron beam evaporator using a pressed-powder Gd 2 O 3 target. Films 25 nm thick were shown to be stoichiometric Gd 2 O 3 by Rutherford backscattering and had a dielectric constant at 100 kHz of 16.0 Ϯ 0.3. Transmission electron microscopy and X-ray reflectivity measurements showed that films 7-13 nm thick annealed in oxygen consisted of three distinct layers, an interfacial silicon dioxide layer next to the substrate, a second amorphous oxide layer containing silicon, gadolinium, and oxygen above this, and a polycrystalline Gd 2 O 3 layer on top. Annealing in oxygen reduced the leakage currents, increased the thickness of the silicon dioxide layer, and increased the grain size of the top Gd 2 O 3 layer. The characteristics of the leakage currents through the gadolinium oxide were consistent with a Frenkel-Poole conduction mechanism with a silicon-Gd 2 O 3 band offset of 1.8 V. Interfaces with excellent electrical properties, characteristic of good SiO 2 , were obtained after annealing in oxygen. Annealing of the films in vacuum prior to oxygen annealing reduced the thickness of the interfacial silicon dioxide.

Characterization of gadolinium and lanthanum oxide films on Si (100)

“…4͑a͔͒ again are identical to previous observations. 6,7 The composition is stoichiometric Gd 2 O 3 and the three layer structure observed by HRTEM in the annealed film is evident ͓Fig. 4͑a͔͒.…”

“…[6][7][8] For the as-deposited film, there is a crystalline gadolinium oxide layer and a thin amorphous silicate interfacial layer with a negligible interface oxide layer of Ͻ5 Å in thickness. Three layers were observed in the annealed film: Gd 2 O 3 , (Gd 2 O 3 ) x (SiO 2 ) 1Ϫx , and SiO 2 , respectively.…”

“…Details of the deposition procedures are described elsewhere. 6 The wafers were cut into pieces after deposition and annealed in a Heatpulse 610 ͑Steag RTP Systems͒ rapid thermal processing system in flowing O 2 at 900°C for 2 min. ͗011͘ cross-section transmission electron microscopy ͑TEM͒ samples were prepared following standard procedures and examined in a Philips EM430T operating at 250 kV and a Philips CM20 equipped with field emission gun and an energy loss imaging filter ͑Gatan model 678͒.…”

Thermal stability and diffusion in gadolinium silicate gate dielectric films

“…1 O 3 , and silicates such as ZrSiO 4 and HfSiO 4 . [2][3][4] It is generally assumed that other lanthanide oxides, such as Gd 2 O 3 , [5][6][7] or their silicates, 8 are also thermodynamically stable. However, even a thermodynamically stable film can react if excess oxygen in the film or from the ambient, or Si from the substrate, diffuse through the film and react with each other.…”

Structural comparison of gadolinium and lanthanum silicate films on Si(1 0 0) by HRTEM, EELS and SAED

“…The details of the deposition procedures are described elsewhere [6]. Both the gadolinium and lanthanum silicate ®lms have similar compositions, determined to be M 0.23 Si 0.14 O 0.63 (i.e.…”