J. Ahn

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>>

Oxynitride gate dielectrics for p/sup +/-polysilicon gate MOS devices

Different oxynitride gate dielectrics (NH/sub 3/-nitrided, reoxidized NH/sub 3/-nitrided, N/sub 2/-annealed NH/sub 3/-nitrided, and N/sub 2/O grown oxides) are investigated for use in p/sup +/-polysilicon gate MOS devices. The comparison is based on flatband voltage shift as well as decrease in inversion capacitance. Results show that NH/sub 3/-nitrided and N/sub 2/-annealed NH/sub 3/-nitrided oxides best suppress the boron penetration and, consequently, these two undesirable effects. These findings are explained on the basis of the distribution of nitrogen in various oxynitride dielectrics.<<ETX>>

Time-dependent dielectric breakdown characteristics of N/sub 2/O oxide under dynamic stressing

Time-dependent dielectric breakdown (TDDB) characteristics of MOS capacitors with thin (120-AA) N/sub 2/O gate oxide under dynamic unipolar and bipolar stress have been studied and compared to those with control thermal gate oxide of identical thickness. Results show that N/sub 2/O oxide has significant improvement in t/sub BD/ (2*under-V/sub g/ unipolar stress, 20*under+V/sub g/ unipolar stress, and 10*under bipolar stress). The improvement of t/sub BD/ in N/sub 2/O oxide is attributed to the suppressed electron trapping and enhanced hole detrapping due to the nitrogen incorporation at the SiO/sub 2//Si interface.<<ETX>>

P-channel MOSFET's with ultrathin N/sub 2/O gate oxides

The performance and reliability of p-channel MOSFETs utilizing ultrathin ( approximately 62 AA) gate dielectrics grown in pure N/sub 2/O ambient are reported. Unlike (reoxidized) NH/sub 3/-nitrided oxide devices, p-MOSFETs with N/sub 2/O-grown oxides show improved performance in both linear and saturation regions compared to control devices with gate oxides grown in O/sub 2/. Because both electron and hole trapping are suppressed in N/sub 2/O-grown oxides, the resulting p-MOSFETs show considerably enhanced immunity to channel hot-electron and -hole-induced degradation (e.g., hot-electron-induced punchthrough).<<ETX>>

Electrical properties of MOSFET's with N/sub 2/O-nitrided LPCVD SiO/sub 2/ gate dielectrics

Electrical properties of MOSFETs with gate dielectrics of low-pressure chemical-vapor-deposited (LPCVD) SiO/sub 2/ nitrided in N/sub 2/O ambient are compared to those with control thermal gate oxide. N/sub 2/O nitridation of CVD oxide, combines the advantages of interfacial oxynitride growth and the defectless nature of CVD oxide. As a result, devices with N/sub 2/O-nitrided CVD oxide show considerably enhanced performance (higher effective electron mobility), improved reliability (reduced charge trapping, interface state generation, and transconductance degradation), and better time-dependent dielectric breakdown (TDDB) properties (t/sub BD/) compared to devices with control thermal oxide.<<ETX>>

Improved hot-carrier immunity in CMOS analog device with N/sub 2/O-nitrided gate oxides

The authors report on the hot-carrier effects on analog device performance parameters in CMOS devices with N/sub 2/O-nitrided gate oxides. The hot-carrier-induced degradation has been studied in terms of drain output resistance, voltage gain, differential offset voltage, and voltage swings. Results show that, N/sub 2/O nitridation significantly improves the hot-carrier immunity in these aspects, especially for n-channel MOSFETs. Analog and digital device performance degradations have been compared.<<ETX>>

AC hot-carrier effects in MOSFETs with furnace N/sub 2/O-nitrided gate oxides

AC hot-carrier effects in n-MOSFETs with thin ( approximately 85 AA) N/sub 2/O-nitrided gate oxides have been studied and compared with control devices with gate oxides grown in O/sub 2/. Results show that furnace N/sub 2/O-nitrided oxide devices exhibit significantly reduced AC-stress-induced degradation. In addition, they show weaker dependences of device degradation on applied gate pulse frequency and pulse width. Results suggest that the improved AC-hot-carrier immunity of the N/sub 2/O-nitrided oxide device may be due to the significantly suppressed interface state generation and neutral electron trap generation during stressing.<<ETX>>

Dependence of hot-carrier immunity on channel length and channel width in MOSFETs with N/sub 2/O-grown gate oxides

The authors report on the channel length (0.5-5 mu m) and width (0.6-10 mu m) dependence of hot-carrier immunity in n-MOSFETs with N/sub 2/O-grown gate oxides ( approximately 85 AA). While channel hot-carrier-induced degradation has a strong dependence on channel geometry in control devices, the degradation and its channel geometric dependences are greatly suppressed in devices with N/sub 2/O-gate oxides. Under Fowler-Nordheim injection stress, the control device shows an enhanced degradation with decreasing channel length and increasing channel width, whereas N/sub 2/O device exhibits a less dependence on channel geometry.<<ETX>>

Chemically modified ultrathin oxides fabricated by rapid thermal processing

A comprehensive review of chemical composition and electrical properties is presented for thin gate oxides with small amounts of nitrogen or fluorine, incorporated by rapid thermal processing. Electrical properties of these chemically modified oxides are correlated with the changes in chemical composition and the resulting structural modifications. Qualitative models described in some of the earlier works are used to establish these correlations. It is concluded that the changes in chemical composition of Si02 can be controlled to realize superior gate dielectrics for application in ULSI MOS devices.

Device Performance and Reliability of P-Channel Metal-Oxide-Semiconductor Field Effect Transistors with Chemical-Vapor-Deposited Gate Oxides

This paper reports the performance and reliability of p-channel metal-oxide-semiconductor field effect transistors (MOSFETs) with ultrathin (65 A) low pressure chemical-vapor-deposited (LPCVD) gate oxides annealed in N2 ambient as compared to those with thermal gate oxides of identical thickness. It is shown that MOSFETs with CVD gate oxides exhibit better initial performance (transconductance, current drivability, and effective hole mobility) and enhanced reliability (transconductance degradation, threshold voltage shift, enhancement in gate-induced drain leakage, and hot-electron-induced punchthrough) than the MOSFETs with thermal gate oxides. Furthermore, significantly improved time-dependent dielectric breakdown characteristic of CVD gate oxide has been demonstrated. Strainless CVD SiO2 after proper post-deposition annealing and the substrate-independent film formation mechanism are speculated to result in the improvements in performance and reliability of CVD oxide devices.