Donald R. Young

Electron injection studies on fluorine‐implanted oxides

The effect of fluorine on electron trapping in SiO2 films has been studied by avalanche electron injection. Samples are prepared by 25‐keV fluorine implantation into dry oxides followed by a 1000 °C N2 ambient anneal. Bulk electron traps with capture cross sections on the order of 10−17–10−19 cm2, which are not due to implantation damage, are filled by avalanche electron injection. An optimum dosage of fluorine implantation to suppress the so‐called turnaround effect during avalanche injection exists. This suggests that fluorine might passivate slow interface donor states or reduce bulk hydrogen diffusion. The observation that high‐temperature (120 °C) injection can eliminate most fast and slow interface states for conventional oxides is also true for fluorinated oxides. Our results indicate an enhanced generation of fast donor states for oxides containing fluorine. These states contribute a positive charge when the Fermi level is in the lower portion of the band gap.

Charge trapping in SiO2

Avalanche injection techniques are extensively used to inject electrons and holes from silicon into the thin SiO2 layer of the type used in MOS transistors. This makes it possible to evaluate the electron and hole trapping kinetics in this material using only simple MOS devices. The simplicity of these devices makes it relatively easy to study the effect of variations in the processing technology used. The results show that processing dependencies are different for “bulk” traps and traps located at the Si-SiO2 interface. It is interesting to note that both the hole and electron traps located at the interface have the same processing dependence and are very sensitive to treatments in oxygen suggesting that these traps are related to an oxygen deficiency in the SiO2 near the interface.

New methods for using the Q‐V technique to evaluate Si‐SiO2 interface states

The Q‐V technique applied to metaloxide silicon capacitors makes it possible to measure the silicon‐oxide interface potential directly with only a few simple assumptions. From these data of interface potential versus gate voltage it is possible to calculate the interface state distribution. The Q‐V technique can be used over the entire band gap range and separate n‐ and p‐type samples are not required. New simplified techniques for doing this are presented. The measurements can also be used to determine the band gap of the semiconductor which should have application for the study of silicon‐germanium alloys.

IMPROVEMENT OF THE SIO2/SI INTERFACE OF METAL-OXIDE-SEMICONDUCTOR DEVICES USING GATE DIELECTRICS FORMED BY NF3-AIDED OXIDATION AND N2O POST-ANNEALING

With the increasing requirement for ultrathin gate dielectrics in advanced metal‐oxide‐semiconductor structures, a low thermal budget process to grow thin dielectric film is vital, while at the same time maintaining the good interface quality and thin film reliability. In this article, thermal nitridation of fluorinated oxide in N2O ambient was investigated. While fluorinated oxides provide a lower thin film stress and better interface than conventional oxides, an excess amount of fluorine in the starting oxide has an adverse effect on the high field stability. For N2O‐nitrided oxide, high temperature and prolonged nitridation time reduce the interface state generation ΔDit resulting from avalanche electron injection at the expense of increasing the flatband voltage shift ΔVfb. The electrical properties are strongly process dependent. The best operating window of N2O nitridation of fluorinated oxide (F‐ox), grown at 900 °C with a 100 ppm NF3 additive, lies between 30 and 120 min at 950 °C. With careful co...

Effect of germanium implantation on metal‐oxide‐semiconductor avalanche injection

The effect of germanium on the hot electron current of a metal‐oxide‐semiconductor device has been studied by avalanche electron injection from the silicon to the silicon dioxide. Different doses of germanium ranging from 1012 to 1015 atoms/cm2 are implanted into the Si‐SiO2 interface. The ‘‘lucky’’ hot electron population is suppressed by the germanium implantation. We have used the charge‐voltage technique to measure the interface state density. The interface state density increase caused by the Ge implantation is negligible if the dose is lower than 1014 Ge/cm2. Our results show that the Ge implantation is a promising method to solve the hot carrier problem that has become important in submicrometer devices.

Comparison of symmetrical and asymmetrical hot-electron injection in MOS transistors

Abstract The effect of nonuniform injection and trapping on the characteristics of long-channel MOS transistors is investigated. Long-channel transistors are symmetrically injected with carriers introduced from adjacent diode stripes which are parallel to the length of the transistor. Asymmetrical injection is performed by introducing carriers from diodes which are closer to the drain of the device under test. The rate of change in the extrapolated threshold voltage is higher for asymmetrical injection, since the same amount of injected charge is submitted to a smaller portion of the channel region. The maximum transconductance rises over the period of stressing for the asymmetrical injection situation, while the transconductance consistently decreases with stress time for symmetrical injection.