Nitrogen plasma annealing for low temperature Ta2O5 films

Abstract

A low temperature oxygen/nitrogen plasma process is reported that substantially reduces leakage currents in chemical vapor deposited (CVD) and physical vapor deposited (PVD) films of tantalum oxide. We show that a combination of nitrogen and oxygen in a remote downstream microwave plasma source reduces leakage currents in CVD films of tantalum oxide and also reduces trap densities as measured by charge pumping. The as deposited CVD films show a high level of photoluminescence that is substantially lowered by the plasma anneal due to a reduction in the density of midgap states. For films deposited by PVD in the thickness range of 100 nm we find low leakage currents with a substantial improvement from the introduction of nitrogen into the plasma. However, PVD films in the thickness range of 20 nm show larger relative leakage currents and less of an improvement from the addition of nitrogen. The role of nitrogen in lowering leakage currents and charge trapping is thought to occur from a reduction in the density of bulk trap states in the oxide due to partial incorporation of nitrogen in the oxide. Both of these low temperature deposition and annealing processes are compatible with integration into the upper levels of metallization for high density circuits.

Crystallization improvement of Ta2O5 thin films by the addition of water vapor

“…As one of the alternative gate dielectric materials, tantalum pentoxide (Ta 2 O 5 ) has been studied extensively in applications such as storage capacitors in dynamic random access memory (DRAM), gate oxide in field effect transistors (FET) due to its high permittivity, high refractive index, excellent step coverage, and tolerable dielectric strength [1][2][3]. Recently, promising applications of Ta promoted even greater interests [4]. Although much research effort has been devoted to the structural and electrical properties of the materials, as-deposited Ta 2 O 5 thin films still suffer from the crystallization difficulty and poor electrical properties [5][6][7][8].…”

High‐Mobility Low‐Voltage ZnO and Li‐Doped ZnO Transistors Based on ZrO2 High‐k Dielectric Grown by Spray Pyrolysis in Ambient Air

“…[ 18 ] Oxide transistors based on high -k dielectrics have received the most attention and a number of high mobility, low-voltage devices have been demonstrated. [ 15 , 17 ] The high -k materials studied to date include transition metal oxides such as Ta 2 O 5 , TiO 2 , [19][20][21][22] ZrO 2 , [23][24][25][26] Al 2 O 3 , [ 27 ] HfO 2 , [ 28 ] and silicates, [ 29 ] as well as ferroelectric materials such as Pb(Zr,Ti) O 3 and (Ba,Sr)TiO 3 . [ 30 , 31 ] Among these, ZrO 2 and HfO 2 are the most extensively studied dielectrics and are widely considered to be excellent candidates because of their relatively high dielectric constants, good thermal stability, and large band gaps.…”

Dielectric function of amorphous tantalum oxide from the far infrared to the deep ultraviolet spectral region measured by spectroscopic ellipsometry

“…Prior to application of sputter-deposited films it is necessary to understand the relation between microstructure, growth conditions, and resulting electrical and optical properties. A through optical study of such microstructure related effects was shown previously for magnetron sputtered boron nitride thin films [18][19][20][21] Tantalum oxide films ͑TOF͒ have been grown by a large variety of physical vapor deposition and chemical vapor deposition ͑CVD͒ processes, including ion beam sputtering, 22,23 magnetron sputtering, 2,7,9,24 ͑low temperature͒ thermal oxidation, 9,25 anodization, 26 ion plating, 1,27 electronbeam evaporation, 4,27 laser ablation, 28,29 low pressure CVD, 14,30 photo-CVD, 31,32 atomic layer deposition, 33 and plasma-enhanced CVD. 12,16,34 A metalorganic solution deposition technique 6 was also used to grow TOF.…”