Oxynitride films grown on preoxidized (100) silicon surfaces in a nitric oxide (NO) ambient at 950 °C have been investigated using x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), and cross-sectional transmission electron microscopy (XTEM). Compared to N2O oxynitride, NO oxynitride exhibits very different surface chemistry, interface properties, and growth mechanisms. The etch back of NO and N2O oxynitride films allows control of sample thickness for the XPS measurements. NO oxynitride has the interfacial nitrogen (Nint) sharply peaked on the Si substrate side of the interface, while it is broad and on the dielectric side of the interface for the N2O oxynitride. The N(1s) XPS results reveal a clear distinction between N2O oxynitride and NO oxynitride. Near the Si/dielectric interface the NO oxynitride shows primarily Si≡N bonds, while the N2O films showed a N(1s) binding energy peak that is in-between that of Si≡N bonds and Si2=N—O bonds. Furthermore, the NO oxynitride surface roughness as determined by AFM is lower than that of the Si/SiO2 interface.
This letter presents a unique process to grow high quality ultrathin (∼60 Å) gate dielectrics using N2O (nitrous oxide) gas. Compared with conventional rapid thermally grown oxide in the O2, the new oxynitride dielectrics show very large charge-to-breakdown (at +50 mA/cm2, 850 C/cm2 for oxynitride compared to 95 C/cm2 for the control thermal oxide) and less charge trapping under constant current stress. Significantly reduced interface state generation was also observed under constant current stress and x-ray radiation. A secondary-ion mass spectroscopy depth profile indicates a nitrogen-rich layer at the Si/SiO2 interface, which can explain the improved integrity of oxynitride dielectric.
Film characteristics of thin oxynitride dielectrics grown in nitrous oxide (N20) and nitric oxide (NO) gas ambients at 950°C were investigated by secondary ion mass spectrometry, x-ray photoelectron spectroscopy, atomic force microscopy (AFM), and cross-sectional transmission electron microscopy. Compared to N20 oxynitride, NO oxynitride exhibits very different surface chemistry, interface properties, and growth phenomena. NO oxynitride has the N, sharply peaked on the Si substrate side of the interface, while it is broad and on the dielectric side of the interface for the N,O oxynitride. The N (is) XPS results reveal a clear distinction between N2O oxynitride and NO oxynitride. Near the Si/dielectric interface the NO oxynitride shows primarily SiN bonds, while the N20 films showed a N (is) binding energy peak that is in between that of SiN bonds and Si2=N-O bonds. Further, the NO oxynitride surface roughness as determined by AFM is lower than that of the Si/SiO2 interface. The film characteristics of N20 and NO oxynitrides after reoxidation in 0, ambient are different. An anomalous increase in N, content and a decrease in oxygen content of these oxynitrides were observed as a result of reoxidation in oxygen ambient. These results are explained on the basis of changes in matrix composition of reoxidized oxynitride films. InfroductionOxynitrides grown in nitrous oxide (N2O) and nitric oxide (NO) gas ambients have drawn attention as candidates for gate dielectric and tunnel dielectric for submicron devices due to process simplicity and excellent reliabilityt23 Some benefits of these oxynitrides are as follows"'5: oxynitride decreases trapping rates and increases charge-to-breakdown (Qbd), improves N channel transconductance (g,,) under high gate bias, and increases hot carrier immunity (HCI). Oxynitride also enhances endurance in electrically erasable and programmable readonly memory (EEPROM), and inhibits boron penetration from p°-gates.'4'5 These improvements are due to accumulation of nitrogen atoms at the Si/SiO2 interface.Generally the results for NO oxynitrides were superior to those obtained with N2O oxynitrides.'2'3 Much lower thermal budget can be used for an NO oxynitride process compared to an N20 oxynitride process. This motivated us to examine the physical aspects of N20 and NO oxynitride more closely. This article is a report on growth and film characteristics of N20 and NO oxynitride films as studied primarily by secondary ion mass spectroscopy (SIMS) measurements. In addition, x-ray photoelectron spectroscopy (XPS), AFM, and cross-sectional transmission electron microscopy (XTEM) techniques were employed to characterize these dielectrics.Recently for the first time the reoxidation of NO oxynitride gate dielectric was studied.'6'7 Reoxidation resulted in a striking enhancement of both gate and substrate injection charge-to-breakdown (Qb,) by 3 -5 times for active edge intensive capacitors in comparison to thermal oxide, N2O, and NO oxynitride. In addition, reoxidized N20 oxynitrides showed improvemen...
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