Oxynitridation of Silicon and Postnitridation of Thermal Silicon Oxide in N 2 O in a Vertical Furnace

Thermal oxidation of silicon in nitrous oxide false(N2Ofalse) ambient at pressures from 1 to 4 atm has been studied. We show that the oxidation rate is different from the one predicted by the Deal-Grove model for normal oxidation in dry oxygen. In our case, the dependence observed for the oxide thickness as a function of the oxidation time is of the form x=x0+false(γt)β, where x0 is a native oxide thickness. For the temperature range between 900 and 1200°C, and 2 atm of pressure, the activation energy for γ is around 1.18 eV. In addition, the exponential factor β (at 1000°C) varies as the square root of the N2O pressure. These results indicate that thermal oxidation in N2O behaves in a completely different way than normal oxidation, very likely due to the influence of chemical reactions in the gas phase, to the catalytic influence of the N2OSiO2 interface, and to the incorporation of nitrogen into the oxide film itself. The results presented here establish the basis for the development of a more complete model for thermal oxidation of silicon in a N2O ambient. © 2001 The Electrochemical Society. All rights reserved.

Section: Resultssupporting

confidence: 91%

Thermal Oxidation of Silicon in Nitrous Oxide at High Pressures

Morales‐Acevedo

Santana

Carrillo-López

2001

“…Coulomb scattering is dominated by doping impurities in low-field areas and dominated by interface roughness in high-field areas. 4,16,19 In a deep submicrometer n-MOSFET, the transverse electric field ͑that is, the field orthogonal to the gate oxide interface͒ attains values higher than 1 MV/cm, and the energy levels of the channel electrons are strongly quantized even at room temperature, while scattering with surface imperfections degrades electron mobility. Since the typical effective electric field at the threshold is close to or higher than 0.5 MV/cm, the mobility of today's MOSFET is always surface roughness-limited.…”

Section: Resultsmentioning

confidence: 99%

“…Wafers are processed sequentially through these three modules, without exposure to air, thus obtaining native-oxide-free poly-Si/SiO 2 /Si MOS capacitors. 16 The effects of in situ HF vapor cleaning and N 2 ϩ implantation on n-MOSFET performance are discussed herein.…”

Section: Methodsmentioning

confidence: 99%

Nitrogen Implantation and In Situ HF Vapor Clean for Deep Submicrometer n-MOSFETs

Chen

Lei

Chen

et al. 2002

This work describes a high performance and reliable deep submicrometer n-channel metal oxide semiconductor field effect transistor ͑n-MOSFET͒ with ultrathin gate oxide prepared by combining nitrogen gate electrode implantation and native-oxidefree in situ HF vapor preoxidation cleaning. The results herein reveal that the performance and reliability, including the leakage current of the ultrathin gate oxide, charge-to-breakdown, drain current, transconductance, charge pumping current, stress induced leakage current, and hot carrier reliability of n-MOSFETs are all significantly improved. The enhanced reliability and performance are attributed to the native-oxide-free process, smooth interface, and reduced incorporation of As in the gate oxide which results from HF vapor cleaning and nitrogen implantation.The reliability challenges of ultrathin gate oxide are becoming increasingly greater for deep submicrometer complementary metal oxide semiconductors ͑CMOS͒ devices. 1,2 As the gate oxide thickness scales down, causing soft breakdown and direct tunneling effects, removal of the native oxide prior to gate oxidation becomes critical. Hence, the HF vapor clean and in situ native oxide desorption process have been investigated extensive. 3,4 The postoxidation anneal ͑POA͒ and/or oxynitridation process may enhance the trapping and hot carrier immunity properties of gate oxides by improving interface smoothness and/or increasing interfacial nitrogen concentration. 5,6 Nitrogen implantation has recently received increasing attention in the fabrication of deep submicrometer devices. 7 Nitrogen was implanted ͑i͒ into poly-Si gates to suppress boron penetration, 8-11 ͑ii͒ into junctions to improve the junction leakage, 12,13 and ͑iii͒ into substrates to enhance n-channel metal oxide semiconductor field effect transistor ͑n-MOSFET͒ device performance. [12][13][14][15] The hot carrier resistance of both n-and p-MOSFETs was also found to be capable of substantial improvement by incorporating nitrogen in the gate oxide by implanting it through a polysilicon gate. 11 This work describes a high performance and reliable deep submicrometer n-MOSFET with ultrathin gate oxide prepared by combining nitrogen gate electrode implantation and native-oxide-free in situ HF vapor preoxidation cleaning. Additional in situ HF vapor cleaning and the transfer of wafers in the closed ambient can reduce the regrowth of native oxide and improve surface roughness. Furthermore, the device will benefit from low arsenic incorporation at the oxide/silicon interface in the nitrogen implantation samples. Consequently, the performance and reliability is significantly improved, including the leakage current of ultrathin gate oxide, chargeto-breakdown (Q bd ), the drain current (I d ), transconductance (G m ), charge pumping current (I cp ), stress induced leakage current ͑SILC͒, and hot carrier reliability of n-MOSFETs with 4 nm thin gate oxides. ExperimentalThe gate oxidations and polysilicon deposition were performed in the Advance 400 ͑ASM A400/3͒, a clus...

“…28 Nitrogen incorporation into thermal SiO 2 usually requires gases other than N 2 . 29 An extended N 2 exposure of an SiO 2 film at temperatures greater than 1000ЊC is necessary for nitrogen incorporation into a thermal oxide. 30 Most thermal oxide processes employ an N 2 annealing step prior to growth and occur at temperatures less than 1000ЊC.…”

Section: Discussionmentioning

confidence: 99%

Surface Residue Island Nucleation in Anhydrous HF/Alcohol Vapor Processing of Si Surfaces

Carter

Hauser

Nemanich

2000

Anhydrous HF/methanol vapor-phase chemistries were employed to etch SiO 2 /Si surfaces at low pressure (5-50 Torr) and ambient temperature. The oxides on Si were formed from the following: (i) RCA chemical cleaning and (ii) UV-ozone treatment. Atomic force microscopy (AFM) and lateral force microscopy (LFM) were used to analyze the HF vapor-cleaned Si surfaces. AFM/LFM displayed residue islands distributed randomly upon the Si surface as a result of vapor-phase cleaning. As a result of etching RCA chemical oxides, the average lateral dimension of the residue islands is 40 nm and the average height of the islands is 6 nm. As a result of etching UV-ozone oxides, the average lateral dimension of the residue islands is 30 nm, and the average height of the islands is 3.5 nm. A decrease in residue island density is observed after the removal of a UV-ozone oxide compared to RCA chemical oxide removal. Secondary ion mass spectroscopy was used to characterize chemical impurities (O, C, F, and N) in the SiO 2 films and and the Si surface after HF vapor-phase cleaning. The constituents of the residue islands have been attributed to nitrogen impurities and silicon atoms imbedded in the passivating oxides. Results indicate that condensation of methanol vapor onto the bare Si surface, after oxide removal, is necessary for residue island formation. We suggest a model in which residue island nucleation occurs from nonvolatile N-Si complexes that form hydrogen bonds with methanol molecules and diffuse into the adsorbed alcohol layer. The molecular impurities then interact and form residue islands. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.216.129.208 Downloaded on 2015-03-22 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.216.129.208 Downloaded on 2015-03-22 to IP