Reliability of ultrathin nitrided oxides grown in low pressure N2O ambient

The influence of N₂O oxynitridation and oxidation pressure on reliability of ultrathin gate oxides from 4 down to 2.5 nm thickness was investigated. A set of different oxidation parameters was applied during oxide growth which comprised oxidation pressure and N₂O partial pressure during rapid thermal oxidation. The reliability of the oxides was tested by constant voltage stress. Evaluation of the resulting times to soft breakdown (t_sbd) for different stress voltages allows to predict a supply (gate) voltage V^10y,max providing an oxide lifetime of 10 years. For this extrapolation, t_sbd was assumed to increase exponentially as stress voltage is reduced. The slope of the extrapolation is found to become steeper as oxides become thinner, which implies higher V^10y,max and thus higher reliability for thinner oxides as under an assumption of a uniform slope for all thicknesses. Further, the results of this extrapolation demonstrate that oxidation in N₂O containing ambient can improve oxide reliability for ultrathin gate oxides.     

High-field-induced leakage in ultrathin N2O oxides

Stress-induced leakage current (SILC) is studied in ultrathin (~50 Å) gate oxides grown in N₂O or O₂ ambient, using rapid thermal processing (N₂O oxide or control oxide, respectively). MOS capacitors with N₂O oxides exhibit much suppressed SILC compared to the control oxide for successive ramp-up, constant voltage DC, and AC (bipolar and unipolar) stresses. The mechanism for SILC is discussed, and the suppressed SILC in N₂O oxide is attributed to suppressed interface state generation due to nitrogen incorporation at the Si/SUO₂ interface during N₂O oxidation     

Uniform durable thin dielectrics prepared by rapid thermalprocessing in an N2O ambient

Thin dielectrics grown on silicon wafers by rapid thermal processing in an N₂O ambient at temperatures of 1100°C, 1150°C, and 1200°C are discussed. The resulting films, in conjunction with an O₂ ambient control were characterized by thickness measurements and electrical performance. Dielectrics formed in N₂O in this temperature range were all superior to that prepared in an O₂ ambient in terms of interface state generation and flatband voltage shift after constant current stressing. Although all N₂O prepared samples exhibited similar cross wafer electrical uniformity, higher growth temperatures favored thickness uniformity. The electrical behavior of the N₂O wafers was not strongly dependent on growth temperature; however, a 60-s 1100°C post-oxynitridation N₂ anneal was found to significantly reduce subsequent electrical performance. It is also demonstrated that under optimum process conditions, high-quality uniform dielectrics can be formed by RTP in N₂O     

P-channel MOSFET's with ultrathin N2O gate oxides

The performance and reliability of p-channel MOSFETs utilizing ultrathin (~62 Å) gate dielectrics grown in pure N₂O ambient are reported. Unlike (reoxidized) NH₃-nitrided oxide devices, p-MOSFETs with N₂O-grown oxides show improved performance in both linear and saturation regions compared to control devices with gate oxides grown in O₂. Because both electron and hole trapping are suppressed in N₂O-grown oxides, the resulting p-MOSFETs show considerably enhanced immunity to channel hot-electron and -hole-induced degradation (e.g., hot-electron-induced punchthrough)     

Slow-trap profiling of NO and N2O nitrided oxides grown on Si and SiC substrates

In this paper, we demonstrate the unique ability of a newly developed slow-trap profiling technique to characterise silicon-based MOS capacitors in strong inversion. We also demonstrate the applicability of the slow-trap profiling technique for the characterisation of oxides grown on SiC. The obtained slow-trap profiles show that NO nitridation eliminates while N₂O creates defects acting as slow traps in the case of both Si and SiC substrates. The corresponding effects of nitridation on interface traps and fixed oxide charge are also discussed.     

The electrical characteristics of polysilicon oxide grown in pure N2O

N₂O was used to grow silicon polyoxide. It was found that the N₂O-grown polyoxide had a lower leakage current but a higher breakdown field when the top-electrode was positively biased. This is opposite to that of conventional O₂-grown polyoxide. Moreover, it had less electron trapping when stressed and a larger charge-to-breakdown     

Charge-trapping properties of poly-silicon oxides by rapid thermal N2O process

The polyoxide with nitrogen incorporation by RTN₂O process can obtain smoother interface of the polyoxide/polysilicon, thus improving the characteristics of polyoxides. However, too much nitrogen does not improve, instead, degrades, the quality of the polyoxide and to induce thickness non-uniformity. It can be found that initial hole-trapping phenomenon was observed in the polyoxides grown by rapid thermal N₂O oxidation process and the higher the growth temperature is, the larger the hole-trapping rate is. The larger hole-trapping is due to more excessive nitrogen release in short time at the polyoxide/polysilicon interface at high temperature oxidation, which may induce large undulations at the Si/SiO₂ interface and result in localized high electric fields to obtain smaller Qbds. However, the charge-trapping properties can be improved by the N₂O-annealed process at proper temperature due to proper amount of nitrogen incorporated into the polyoxide and piled up at the interface.     

Nitrogen bonding configurations near the oxynitride/silicon interface after oxynitridation in N2O ambient of a thin SiO2 gate

The identification of the bonding environments and their progressive modifications upon reaching the oxynitride/silicon interface, in a SiO₂/SiO_xN_y/Si structure, have been investigated by means of X-ray photoemission spectroscopy (XPS). The SiO₂ film was grown at 850 °C by means of a mixed dry-steam process, followed by a 60 min, 950 °C furnace oxynitridation in N₂O gas. A depth profile analysis was carried out by a progressive chemical etching procedure, reaching a residual oxide thickness of about 1.2 nm. XPS analysis of the Si 2p and N 1s photoelectron peaks pointed out that the chemistry of the oxynitride layer is a rather complex one. Four different nitrogen bonding environments were envisaged. Both the overall nitrogen content, which rises up to 2.5%, and its bonding configurations are progressively changing while moving towards the silicon interface.     

High quality interpoly-oxynitride grown by NH3nitridation and N2O RTA treatment

In this letter, a method to grow high quality interpolysilicon-oxynitride (interpoly-oxynitride) film is proposed. Samples, nitridized by NH₃ with additional N₂O annealing and CVD TEOS deposited on poly-oxynitride (poly-I) with RTA N ₂O oxidation, show excellent electrical properties in terms of very high electric breakdown field, low leakage current, high charge to breakdown, and low electron trapping rate. This novel film is a good candidate for an interpoly dielectric of future high density EEPROM and flash memory devices     

选频N_2O激光器

N_2O是线性非对称分子,它的激光工作能级为(001)和(100)振动态以及相联系的转动态,由于下工作能级(100)可以向基态(000)进行偶极跃迁,所以粒子数反转密度较低,加之N_2O气体在高温下容易分解,这些都会使激光功率低于CO_2激光。为了克服这些不利因素,我们采取流动工作气体方式获得连续的激光输出。 激光管长为2100毫米,放电长度为1800毫米,放电管内径20毫米。腔体的一端由NaCl布氏窗封密构成半外腔。金膜全反凹面镜曲率半径为10米,选频用的金属基底光栅为100条/毫米、闪耀波长10.6微米的原刻光栅。激光管装有进气口和出气口,分别与气源钢瓶和抽气泵相联,抽气速率8升/秒,折算管内流速25米/秒。     

Effects of nitridation pressure on the characteristics of gatedielectrics annealed in N2O ambient

Effects of N₂O pressure during oxynitridation on the characteristics of ultrathin gate dielectrics have been investigated. Reoxidation in N₂O ambient showed three distinguished oxidation regions as a function of tube pressure; that is, enhancement at 10-40 torr, retardation at 40-100 torr, and enhancement at 100-600 torr. The N₂O-nitridation at 40 torr incorporated much less nitrogen in oxide bulk than that at near-atmospheric pressure. The 40 torr N₂O-nitridation case exhibited about 70% of nitrogen incorporation at the Si/SiO₂ interface compared to that of the 600 torr N₂O-nitridation case. The low-pressure N₂ O-nitridation at 40 torr results in improvement of TDDB of gate dielectrics and the transconductance of nMOSFETs compared to the nitridation at near-atmospheric pressure. These data suggest that low pressure oxynitridation should be more recommendable for device application     

Effect of N2O nitridation on the electrical properties of MOS gate oxides

Furnace annealing in N₂O is a convenient technique for improving the reliability of thermal oxides without significant modifications of the process flow. We investigate the impact of N₂O nitridation on MOSFET device performance, assessing the various factors contributing to the observed degradation of electron mobility. Estimates based on low-frequency C-V and charge pumping measurements show that nitridation causes a significant increase of the interface trap density in the vicinity of the conduction band. Interface traps contribute a parasitic component to the gate-channel capacitance, thus leading to an overestimate of the inversion charge. This effect accounts for a substantial fraction of the mobility degradation which is observed for the nitrided devices. The remaining degradation can be ascribed to an enhancement of Coulomb scattering, maybe due to differences in dopant segregation, and to a change of the surface roughness characteristics.     

Statistics of soft and hard breakdown in thin SiO2 gate oxides

Assuming that there are circuit applications which can tolerate one or several soft breakdown events before failure, we study the implications of soft/hard breakdown prevalence ratios on the device failure statistics. Our results demonstrate that these two breakdown modes are triggered by the same type of defect-related path, showing identical statistics if considered as independent breakdown mechanisms. An energy dissipation model for the breakdown current runaway transient is presented as a possible way to model soft and hard breakdown prevalence ratios as a function of stress conditions and sample characteristics.     

Reduction of leakage current in chemical-vapor-deposited Ta2O5 thin films by furnace N2O annealing

In this brief, we present a post-deposition annealing technique that employs furnace annealing in N₂O (FN₂O) to reduce the leakage current of chemical-vapor-deposited tantalum penta-oxide (CVD Ta₂O₅) thin films. Compared with furnace annealing in O₂ (FO) and rapid thermal annealing in N ₂O (N₂O), FN₂O annealing proved to have the lowest leakage current and the most reliable time-dependent dielectric breakdown (TDDB)     

Studies of CW lasing action in CO2-CO,N2O-CO, CO2-H2O, and N2O-H2O mixtures pumped by blackbody radiation

A proof of principle experiment to evaluate the efficacy of CO and H₂O in increasing the power output for N₂O and CO ₂ lasing mixtures has been conducted and theoretically analyzed for a blackbody radiation-pumped laser. The results for N₂ O-CO, CO₂-CO, N₂O-H₂O and CO₂-H₂O mixtures are presented. Additions of CO to the N₂O lasant increased power up to 28% for N₂O laser mixtures, whereas additions of CO to the CO₂ lasant, and the addition of H₂O to both the CO₂ and N₂O lasants, resulted in decreased output power     

Properties of Mn-doped Cu2O semiconducting thin films grown by pulsed-laser deposition

Semiconducting oxides offer the potential for exploring and understanding spin-based functionality in a semiconducting host material. Theoretical predictions suggest that carrier-mediated ferromagnetism should be favored for p-type material. Cu₂O is a p-type, direct wide bandgap oxide semiconductor that may hold interest in exploring spin behavior. In this paper, the properties of Mn-doped Cu₂O are described. Activities focused on understanding Mn incorporation during thin-film synthesis, as well as magnetic characterization. The epitaxial films were grown by pulsed-laser deposition. X-ray diffraction was used to determine film crystallinity and to address the formation of secondary phases. SQUID magnetometry was employed to characterize the magnetic properties. Ferromagnetism is observed in selected Mn-doped Cu₂O films, but appears to be associated with Mn₃O₄ secondary phases. In phase-pure Mn-doped Cu₂O films, no evidence for ferromagnetism is observed.     

Thermodynamic study, compositional and electrical characterization of LPCVD SiO2 films grown from TEOS/N2O mixtures

The theoretical phase diagram describing the growth of SiO₂ films from TEOS and N₂O mixtures within the temperature range 500–1100°C and pressure 0.3 Torr has been obtained, minimizing the total Gibbs energy of the chemical system involved in the deposition. It was found that at temperatures up to 900°C and N₂O/TEOS molar ratios up to approximately 7, the SiO₂ films deposited contained carbon impurities. For higher N₂O/TEOS molar ratios the obtained films are carbon free. SiO₂ films were grown from TEOS/N₂O mixtures in a conventional horizontal low pressure chemical vapor deposition reactor at temperatures of 710°C and 820°C and at a pressure of 0.3 Torr. These films were analyzed using X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, atomic force microscopy and C–V measurements taken on metal–insulator–semiconductor structures formed with the deposited films as insulators. It was found that the films contain carbon impurities the concentration of which decreases with the increase of N₂O/TEOS molar ratio, in agreement with the results of the thermodynamic study. Carbon atoms were 90% bonded to other carbon atoms and only 10% to oxygen. It was found that the films are substoichiometric in oxygen with O/Si atomic ratios ranging between 1.95 and 1.80. The films were found to be positively charged, the charge increasing with N₂O flow and decreasing with deposition temperature.     

Photoluminescence of AlGaAs alloy grown by LP-MOVPE at different temperatures using TBA in N2 ambient

High quality of Al_xGa_1−xAs alloys have been grown by the LP-MOVPE using tertiary-butyl arsine as group V precursor in 100% nitrogen ambient. The photoluminescence (PL) properties of Al_0.25Ga_0.75As alloy grown at different temperature have been studied. The PL peak emission intensity of the samples increases with the substrate growth temperature initially and saturated at the growth temperature 760°C. The emission intensity decreases when further increase the temperature. This is attributed to the oxygen content in the samples.     

High field stressing effects on the split N2O grown thingate dielectric by rapid thermal processing

Highly reliable thin oxynitride layers of very good Si-SiO₂ interface endurance were grown on silicon wafers with a split N ₂O cycle (N₂O/O₂/N₂O) employing rapid thermal processing (RTP). Excellent electrical characteristics with reduced positive charge generation, electron trapping and/or interface state generation were achieved under high field stressing compared to pure N₂O dielectric     

MOS characteristics of ultrathin SiO2 prepared byoxidizing Si in N2O

MOS characteristics of ultrathin gate oxides prepared by furnace oxidizing Si in N₂O have been studied. Compared to control oxides grown in O₂, N₂O oxides exhibit significantly improved resistance to charge trapping and interface state generation under hot-carrier stressing. In addition, both charge to breakdown and time to breakdown are improved considerably. MOSFETs with N₂O gate dielectrics exhibit enhanced current drivability and improved resistance to g_m degradation during channel hot-electron stressing