Influence of Oxygen Content on the Physical and Electrical Properties of Thin Yttrium Oxide Dielectrics Deposited by Reactive RF Sputtering on Si Substrates

Abstract

This paper describes the physical properties and electrical characteristics of thin Y 2 O 3 gate oxides grown on silicon substrates through reactive radiofrequency (RF) sputtering. The structural and morphological features of these films were studied using X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy. We found that the Y 2 O 3 gate film prepared under an argon-to-oxygen flow ratio of 25:5 and annealed at 700°C exhibited a reduced equivalent oxide thickness, gate leakage current, interfacial density of states, and hysteresis voltage; it also showed an increased breakdown voltage. We attribute this behavior to (1) the optimum oxygen content in the metal oxide film preventing amorphous silica or silicate from forming at the Y 2 O 3 /Si interface and (2) the low surface roughness. These materials also exhibit negligible degrees of charge trapping at high electric field stress.

Effects of post-deposition annealing ambient on Y2O3 gate deposited on silicon by RF magnetron sputtering

“…PDA of e-beam evaporated Y 2 O 3 film in O 2 (425-625 • C) [23] and RF magnetron sputtered Y 2 O 3 film in Ar (400-1000 • C) [34] ambient had reduced the leakage current as temperature increased. Similar observation was obtained by reactive RF sputtered Y 2 O 3 films subjected to PDA in N 2 ambient from 600 to 700 • C [38]. Beyond this temperature, the leakage current increased [38].…”

“…Similar observation was obtained by reactive RF sputtered Y 2 O 3 films subjected to PDA in N 2 ambient from 600 to 700 • C [38]. Beyond this temperature, the leakage current increased [38]. On the other hand, a reduction in leakage current was attained by RF magnetron sputtered Y 2 O 3 film when temperature was decreased from 600 to 400 • C in vacuum ambient with the highest leakage current obtained at 500 • C [33].…”

“…Thus, it was believed that the source of O 2 was from the Y 2 O 3 films, in which the O 2 was released from the oxide during PDA. This O 2 would either diffuse inward to the Y 2 O 3 /Si interface or diffuse outward to the PDA ambient [38]. However, the source of O 2 might come from both the ambient gas and Y 2 O 3 film when PDA was performed in O 2 or N 2 O ambient.…”

“…On the other hand, a reduction in leakage current was attained by RF magnetron sputtered Y 2 O 3 film when temperature was decreased from 600 to 400 • C in vacuum ambient with the highest leakage current obtained at 500 • C [33]. All of these annealed films have demonstrated a lower leakage current than the respective as-deposited films [23,33,34,38], except for the aforementioned O 2 annealed Y 2 O 3 film at 425 • C [23]. These findings indicated that the acquisition of the lowest leakage current at different PDA temperature was dependent on the PDA ambient.…”

“…Deposition of Y 2 O 3 films has been done by e-beam evaporation [16,[19][20][21][22][23][24][25][26][27][28], molecular beam epitaxy [29,30], RF magnetron sputtering [31][32][33][34][35], laser ablation [36], RF sputtering [37], reactive RF sputtering [15,38], ion beam sputtering [17,36,[39][40][41], plasma-assisted chemical vapor deposition (CVD) [42,43], pulsed liquid-injection plasma-enhanced metallorganic CVD [4,44], low pressure CVD [45], atomic layer deposition [18,[46][47][48], and ionized cluster beam deposition [49,50] techniques. The quality of deposited Y 2 O 3 film may be attributed to two factors, namely crystallinity of the structure and stoichiometry of the chemical composition.…”