Spectroscopic Charge Pumping Research Articles

Investigation of the Temperature Dependence of Hot-Carrier Degradation in Si MOSFETs Using Spectroscopic Charge Pumping

The temperature dependence of defect generation due to hot-carrier stress (HCS) is investigated in long-channel nMOSFETs with a SiO2 insulator. In order to improve the understanding of hot-carrier degradation, we systematically investigate the impact of temperature on the HCS-induced trap densities and their energetic profiles using standard and spectroscopic charge pumping (CP). With the aid of polyheaters, which can rapidly change the device temperature, recovery of the degradation at higher temperatures is minimized by quickly switching the temperature to the characterization temperature of −60 °C. In order to be able to quantitatively analyze the trap profiles measured with spectroscopic CP, a method for finding the correct capture cross section is suggested. Both CP methods yield comparable results, and it is shown that the same types of defects are created at all temperatures. In agreement with the literature, lower stress temperatures during HCS result in the creation of a larger number of defects for our long-channel devices.

Formation of an N-pair at the Si(001)/α–quartz interface

We conduct a first-principles total energy calculation of the atomic and electronic structures of the N defects near the Si(001)/α–quartz interface. We find that the N atoms preferentially form a pair structure at the Si surface immediately below the interface to minimize the system energy. A silicon-induced gap state (SIGS), which is predominantly localized at the interface, is formed just above the valence band edge of bulk Si. The energy level of the SIGS shifts toward the bulk Si valence band edge as the N pairs accumulate at the interface, indicating that the energy gap in the system increases. The atomic and electronic structures of the Np defects is consistent with the previous core-level spectroscopy and spectroscopic charge pumping results.

Fluorine interface treatments within the gate stack for defect passivation in 28 nm high-k metal gate technology

A novel method of fluorine incorporation into the gate dielectric by gaseous thermal NF3 interface treatments for defect passivation have been investigated in 28 nm high-k metal gate technology with respect to improvement in device reliability. The thermal treatment suppresses physical interface regrowth observed in previous plasma-assisted fluorine treatments. Detailed defect characterization by spectroscopic charge pumping is used to characterize the influence of fluorine on trap states in the interfacial oxide layer. Comprehensive structural as well as electrical characterization linked with bias temperature instability measurements indicates the potential of improving reliability in high-k metal gate technology by gaseous introduction of fluorine into the gate dielectric.

Experimental Investigation of Hole Transport in Strained $\hbox{Si}_{1 - x}\hbox{Ge}_{x}/\hbox{SOI}$ pMOSFETs—Part I: Scattering Mechanisms in Long-Channel Devices

This paper presents a wide experimental study of hole transport in SiGe pMOSFETs. Various Ge contents, from 20% up to 60%, and growth templates [unstrained or tensely strained silicon-on-insulator (SOI)] were screened in order to study the influence of various strain levels and Ge concentrations. Electrical results have been compared with the amount of strain in the channel, characterized through dark-field electron holography and nano-beam electron diffraction. The SiGe channel/oxide interface has been investigated through spectroscopic charge pumping and low temperature measurements. We found the signature of Ge-induced defects, particularly near the valence band. The different scattering mechanisms limiting the hole mobility in long-channel transistors have been decorrelated and discussed in the light of the different experimental data provided. We have shown in particular the low contribution of alloy scattering in the SiGe devices under study, and that carrier transport is dominated by the strain effect for Ge content up to 40%. The roughness parameters of the SiGe channel/oxide interface are also modified, with a less prejudicial impact on mobility. The effect of strain and Ge content on the different scattering mechanisms has been established. The combination of all the scattering contributions leads to a maximum mobility at room temperature for a Ge content <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ge</sub> = 0.4 on an SOI template, or equivalently, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ge</sub> = 0.6 on a strained SOI template.

A study of N-induced traps due to a nitrided gate in high-κ/metal gate nMOSFETs and their impact on electron mobility

We report an experimental study of the defects induced by a TiN metal gate. Nitrogen-induced defects due to diffusion from the nitrided gate have been evidenced. The energy profile of the density of interface states in the silicon band gap has been extracted by original spectroscopic charge pumping measurements. We have identified two specific peaks near the Si band edges as the signature of N diffusion. The density of defects has then been correlated to the electron mobility degradation and compared to a theoretical model which well reproduces the experimental data.

Spectroscopic charge pumping investigation of the amphoteric nature of Si/SiO2 interface states

The amphoteric nature of Si/SiO2 interface states in submicron sized metal-oxide-silicon-field-effect-transistors is observed using an enhanced spectroscopic charge pumping method. The method’s simplicity and high sensitivity makes it a powerful tool for interrogating the true nature of electrically measured interface states in samples which exhibit extremely low defect densities. The spectroscopic results obtained clearly illustrate a signature “double peak” density of states consistent with amphoteric Pb center data obtained from electron spin resonance measurements. Since the method is a hybrid of the commonly used charge pumping methodology, it should find widespread use in electronic device characterization.

Spectroscopic charge pumping in Si nanowire transistors with a high-κ/metal gate

The density of interface states has been investigated experimentally on silicon nanowire transistors (SNWTs), with a high-k/metal gate stack. Low temperature measurements down to 25 K have been performed to determine the interface trap energy distribution throughout the Si band gap on nanowire devices. We have shown that SNWTs exhibit a higher trap density together with a modified energy profile as compared to conventional planar devices. Finally these spectroscopic measurements have been compared to electron mobility to complete the analysis and to further understand the impact of the interface on carrier transport.

Charge pumping spectroscopy: HfSiON defect study after substrate hot electron injection

Spectroscopic charge pumping (CP) is used to study the evolution of the energy distribution of trapped electrons within HfSiON/SiO 2 gate stacks under substrate hot electron injection (SHEI). Base level CP measurements with large pulse amplitude allow an efficient charging/discharging of traps and reaching two defect bands in the HfSiON situated at 0.40 and 0.85 eV above the Si conduction band, respectively. Unlike standard constant voltage stress (CVS), SHEI enables full control of the stress by separately controlling the applied gate field, the injected electron energy, and the fluence. During CVS, HfSiON defects at 0.40 eV are generated. Conversely, during SHEI, either the shallow or the deep defects are preferentially created depending on the gate field as well as electron energy.

Characterization of interface traps on MOS transistor submicronic by the three level charge pumping

Because of its efficiency, its high precision and its easy use regarding to classical techniques of Si-Sio2 (C-V, DLTS, Conductance...),interface characterization, the charge pumping technique has seen a large evolution these years. Many improvements have been made other, derivation techniques have been developed (at three-level charge pumping, spectroscopic charge pumping ...) This technique is particularly used for very slight geometry MOS transistors damaging, where other techniques have no utility. This damaging often leads to the creation of a fixed trapped charge in the oxide coat and active electronically defaults in the oxide Semi-conductor interface after the application of ageing constraint (ionizing radiation, injection carrier). This ageing is so pronounced when the dimensions are slight this represents the main obstacle that the microelectronics must face. In this article we simulate the three-level charge pumping technique with SPICE3F4 simulator. This simulation will permit the obtaining of spatial and energetic spread of defaults at the interface.

A spectroscopic charge pumping model in spice for the low dimensional MOSFET's

We have simulated the experimental spectroscopic charge pumping technique by the implementation of a model in the electrical simulator SPICE3F4. This model takes into account the temperature effect on the geometrical and electrical parameters of the studied transistor. The simulated results are in a good agreement with recent and different experimental results.

Characterization of Si–SiO2 interface states: Comparison between different charge pumping and capacitance techniques

The three-level and spectroscopic charge pumping techniques, deep level transient spectroscopy and capacitance-voltage measurements are both used to determine the energy distribution of Si–SiO2 interface states on submicrometer metal–oxide–semiconductor field-effect transistors and metal–oxide–semiconductor capacitors. This study is a systematic comparative analysis between charge pumping techniques and capacitance measurements. The measurements have been performed on different structures (n- and p-type materials, low and high interface states densities) and the performances of each technique have been compared.

Post-irradiation formation of Si-SiO2 interface states in a hydrogen atmosphere at room temperature

Si MOSFETs were irradiated with x-rays and then exposed to various partial pressures of H2 at either room temperature or 125 °C. The number of interface traps and the net positive oxide trapped charged were measured during the hydrogen exposure using spectroscopic charge pumping techniques. During the hydrogen exposure the gate electrode was held at a positive bias to maintain a field of 0.65 MV/cm across the gate oxide. It was found that during the room temperature hydrogen exposure the number of interface traps increased by a factor of about two. The change in the oxide trapped charge during hydrogen exposure indicated that the decrease in the number of positively charged oxide traps was approximately the same as the increase in the number of interface traps. The time evolution and bias dependence of these changes are explained by a model that we previously proposed. In this model positively charged radiation induced defects in the oxide crack the H2 to form H+. Under positive gate bias the H+ then drifts to the Si-SiO2 interface where it forms an interface state, while at the same time removing positive charge from the oxide.

Spectroscopic charge pumping: A new procedure for measuring interface trap distributions on MOS transistors

An approach to the application of the charge pumping technique is proposed as a tool for the measurement of interface trap energy distributions in small area MOS transistors. The new approach is spectroscopic in nature, i.e., only one energy window is defined, and forced to move through the bandgap by changing the sample temperature. This method has the advantages of addressing a larger part of the bandgap as compared to the classical approach, of reducing the complication in the processing of the data, and of yielding information about the hole and electron capture cross sections separately. Experiments performed on both n-channel and p-channel MOS transistors reveal that, in the temperature (energy) range studied, the interface-trap distribution is slowly varying with energy and that the trap capture cross section is nearly constant over energy and temperature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>