W. Ting

Electrical characteristics of ultrathin oxynitride gate dielectric prepared by rapid thermal oxidation of Si in N2O

This letter presents a unique process to grow high quality ultrathin (∼60 A) 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.

Electrical and reliability characteristics of ultrathin oxynitride gate dielectric prepared by rapid thermal processing in N/sub 2/O

The electrical and physical characteristics of oxynitride grown in N/sub 2/O gas ambient have been studied. The dielectric growth rate in N/sub 2/O was found to be highly controllable and lower than that in O/sub 2/. Auger electron spectroscopy studies of oxynitride show a nitrogen-rich layer near the Si-SiO/sub 2/ interface. Compared with the control oxide, the oxynitride shows excellent electrical characteristics such as excellent diffusion barrier to dopant (BF/sub 2/), a significant reduction in interface state generation, less electron trapping, and much larger charge-to-breakdown under Fowler-Nordheim stress. A significantly lower threshold voltage shift and degradation of subthreshold swing under hot electron stress were also observed. These improvements can be explained by the nitrogen incorporation at Si-SiO/sub 2/ interface. This new oxynitride shows good promise for future ULSI application.<<ETX>>

Furnace nitridation of thermal SiO/sub 2/ in pure N/sub 2/O ambient for ULSI MOS applications

Furnace nitridation of thermal SiO/sub 2/ in pure N/sub 2/O ambient for MOS gate dielectric application is presented. N/sub 2/O-nitrided thermal SiO/sub 2/ shows much tighter distribution in time-dependent dielectric breakdown (TDDB) characteristics than thermal oxide. MOSFETs with gate dielectric prepared by this method show improved initial performance and enhanced device reliability compared to those with thermal gate oxide. These improvements are attributed to the incorporation of a small amount of nitrogen ( approximately 1.5 at.%) at the Si-SiO/sub 2/ interface without introducing H-related species during N/sub 2/O nitridation.<<ETX>>

Composition and growth kinetics of ultrathin SiO2 films formed by oxidizing Si substrates in N2O

Chemical composition and growth kinetics of ultrathin SiO2 films formed by rapid thermal oxidizing Si substrates in N2O have been studied. Both Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) revealed nitrogen pile‐up at the SiO2/Si interface. Nitrogen concentration at the oxide surface and throughout the bulk was found to be low, similar to reoxidized/nitrided oxides. The nitrogen 1s electron binding energy determined by XPS in the oxide also indicated that these nitrogen atoms were bonded to Si. Electrical characterization showed that N2O oxides exhibited less interface state generation under hot‐electron stressing as compared with the control oxide. Growth kinetics study showed that after an initial stage of fast growth, the oxidation rate was reduced significantly due to the formation of a nitrogen‐rich layer at the Si/SiO2 interface which blocked oxidant diffusion to the interface.

MOS characteristics of ultrathin SiO/sub 2/ prepared by oxidizing Si in N/sub 2/O

MOS characteristics of ultrathin gate oxides prepared by furnace oxidizing Si in N/sub 2/O have been studied. Compared to control oxides grown in O/sub 2/, N/sub 2/O 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 N/sub 2/O gate dielectrics exhibit enhanced current drivability and improved resistance to g/sub m/ degradation during channel hot-electron stressing.<<ETX>>

Study of the composition of thin dielectrics grown on Si in a pure N2O ambient

The composition of ultrathin oxides grown on both [100] and [111]Si substrates in pure N2O in a conventional furnace has been studied using Auger electron spectroscopy (AES) analysis, chemical etching, and electrical measurements. Results show a peak nitrogen concentration at the Si‐SiO2 interface which decreases from the Si‐SiO2 interface to the oxide surface. This nitrogen distribution is responsible for superior electrical properties of metal‐oxide‐semiconductor (MOS) devices with these films as gate dielectrics.

High-quality MOSFETs with ultrathin LPCVD gate SiO/sub 2/

MOSFETs and MOS capacitors with ultrathin (65 AA) low-pressure chemical vapor deposition (LPCVD) gate SiO/sub 2/ have been fabricated and compared to those with thermal SiO/sub 2/ of identical thickness. Results show that the devices with LPCVD SiO/sub 2/ have higher transconductance and current drivability, better channel hot-carrier immunity, lower defect density, and better time-dependent dielectric breakdown (TDDB) characteristics than devices with conventional thermal SiO/sub 2/.<<ETX>>

Growth kinetics of ultrathin SiO2 films fabricated by rapid thermal oxidation of Si substrates in N2O

Growth kinetics of ultrathin SiO2 films formed by rapid thermal oxidizing Si substrates in N2O has been studied in this communication. Results show that the linear‐parabolic law still can be applied to the oxidation of Si in N2O and the interfacial nitrogen‐rich layers in these films result in oxide growth in the parabolic regime by impeding oxidant diffusion to the SiO2/Si interface even for ultrathin oxides. The parabolic rate constant B exhibits an activation energy of 1.42 eV, which is the activation energy for oxidant diffusion in the interfacial nitrogen‐rich layer.

Improved reliability characteristics of submicrometer nMOSFETs with oxynitride gate dielectric prepared by rapid thermal oxidation in N/sub 2/O

Submicrometer MOSFETs with ultrathin oxynitride gate dielectric grown in pure N/sub 2/O ambient were studied. The peak mobility of oxynitride is 5% lower than that of control oxide. However, the oxynitride shows 10% less mobility degradation under high normal field. Compared with the control oxide device, the oxynitride device shows significantly less degradation under channel hot-electron stress. The lifetime of the oxynitride device is approximately one order of magnitude longer than that of the control oxide sample. Significant improvement of device reliability is due to the nitrogen incorporation during the oxidation process.<<ETX>>

High quality thin gate oxide prepared by annealing low‐pressure chemical vapor deposited SiO2 in N2O

In this letter, the electrical properties of thin low‐pressure chemical vapor deposited (LPCVD) SiO2 annealed in N2O ambient have been studied and compared with thermal oxide of identical thickness. It is shown that N2O‐annealed CVD oxide exhibits less interface state generation and less flatband voltage shift under constant current stress than thermal oxide. It also has excellent uniformity and comparable breakdown characteristics. An oxynitride film formation at the Si/SiO2 interface by annealing in N2O is speculated to be the cause of these improvements.