We evaluate the impact of band-to-band tunneling (BTBT) on the characteristics of n-channel junctionless transistors (JLTs) A JLT that has a heavily doped channel, which is fully depleted in the off state, results in a significant band overlap between the channel and drain regions This overlap leads to a large BTBT of electrons from the channel to the drain in n-channel JLTs This BTBT leads to a nonnegligible increase in the off-state leakage current, which needs to be understood and alleviated In the case of n-channel JLTs, tunneling of electrons from the valence band of the channel to the conduction band of the drain leaves behind holes in the channel, which would raise the channel potential This triggers a parasitic bipolar junction transistor formed by the source, channel, and drain regions induced in a JLT in the off state Tunneling current is observed to be a strong function of the silicon body thickness and doping of a JLT We present guidelines to optimize the device for high on-to-off current ratio Finally, we compare the off-state leakage of bulk JLTs with that of silicon-on-insulator JLTs

Effect of Band-to-Band Tunneling on Junctionless Transistors

The purpose of this review article is to report on the recent developments and the performance level achieved in the strained-Si/SiGe material system. In the first part, the technology of the growth of a high-quality strained-Si layer on a relaxed, linear or step-graded SiGe buffer layer is reviewed. Characterization results of strained-Si films obtained with secondary ion mass spectroscopy, Rutherford backscattering spectroscopy, atomic force microscopy, spectroscopic ellipsometry and Raman spectroscopy are presented. Techniques for the determination of bandgap parameters from electrical characterization of metal-oxide-semiconductor (MOS) structures on strained-Si film are discussed. In the second part, processing issues of strained-Si films in conventional Si technology with low thermal budget are critically reviewed. Thermal and low-temperature microwave plasma oxidation and nitridation of strained-Si layers are discussed. Some recent results on contact metallization of strained-Si using Ti and Pt are presented. In the last part, device applications of strained Si with special emphasis on heterostructure metal oxide semiconductor field effect transistors and modulation-doped field effect transistors are discussed. Design aspects and simulation results of n- and p-MOS devices with a strained-Si channel are presented. Possible future applications of strained-Si/SiGe in high-performance SiGe CMOS technology are indicated.

http://iopscience.iop.org/article/10.1088/0268-1242/13/11/002/pdf

Strained-Si heterostructure field effect transistors

We have studied the growth kinetics of the N2O furnace oxynitridation process demonstrating the importance of input flow rate, and therefore gas residence time, in determining the final film thickness and the nitrogen concentration. This dependence on residence time can explain the variation in the tendency to thickness saturation observed in the film growth data reported by several groups. Using published gas phase kinetic data, we have shown that, for a 950 °C oxynitridation process, N2O decomposes into N2, O2, and NO before reaching the wafer load. Again using published information, we have derived a simple equation which describes the subsequent reaction between NO and O2 to produce NO2 as the gas flows down the tube. This reaction results in loss of NO by an amount which depends on the gas residence time and therefore on the input gas flow rate and the dimensions of the system. Since it can be argued that NO2 does not contribute to nitridation, this system‐dependent loss of NO can explain the variation in the reported film growth data. Combining our experimental data and model, we find that the peak nitrogen concentration in the film depends linearly on the NO gas phase concentration. Further, the oxynitride grows more slowly as the NO concentration increases supporting the idea that oxidation sites are blocked by nitrogen as oxynitridation time increases.

Furnace formation of silicon oxynitride thin dielectrics in nitrous oxide (N2O): The role of nitric oxide (NO)

The gas-phase chemistry of silicon oxynitridation in N2O has been investigated. From an evaluation of available kinetic data, we have developed a model for the thermal decomposition of gaseous N2O. To quantify heat transfer between the N2O gas and the wall of the furnace, we introduce the concept of referencing to an N2 gas-temperature profile, measured in an oxidation furnace. Using this model, we can account for the increase with flow rate and temperature of the NO concentration in the N2O decomposition product, and the self-heating during decomposition, for furnace processing. This change in gaseous NO concentration translates to a higher nitrogen content and lower growth rate for the silicon oxynitride. For rapid thermal and other short-gas-residence-time systems, we show that atomic oxygen is present at the Si wafer, and that this removes previously incorporated nitrogen.

Nitrous oxide (N 2 O) processing for silicon oxynitride gate dielectrics

This letter addresses the question of why it is possible to grow high-quality oxide films on N-type but not on P-type SiC. It provides results which indicate that the oxide/SiC interface would be inferior to the oxide/Si interface for both N-type and P-type SiC, if it were not for the beneficial effects of nitrogen incorporation. The letter presents, for the first time, results on nitridation of thermally grown oxides in NO and N/sub 2/O. The results demonstrate that the oxides grown on P-type can be improved by NO annealing, but not by N/sub 2/O annealing.

/pdf/nitridation-of-silicon-dioxide-films-grown-on-6h-silicon-53m1qeli7r.pdf

Nitridation of silicon-dioxide films grown on 6H silicon carbide

The effects of post-oxidation N/sub 2/O anneal on conventional thermal oxide are studied. The oxide thickness increase resulting from N/sub 2/O anneal is found to be self-limiting and insensitive to initial oxide thickness, which makes the thickness of the resulting oxide easy to control. The N/sub 2/O anneal leads to increased resistance against injection-induced interface-state generation and to reduced hole trapping. No further quality improvement is found when the N/sub 2/O-annealed oxide is subject to an additional reoxidation. This finding confirms that nitrogen incorporation in the absence of hydrogen is responsible for improving the quality of the conventional oxides. >

Effects of N/sub 2/O anneal and reoxidation on thermal oxide characteristics

A quantitative model which relates the SOI (silicon-on-insulator) MOSFET breakdown voltage to key parameters such as channel length, SOI film thickness, and gate voltage is presented The SOI breakdown is caused by electron impact ionization current produced near the drain which is subsequently amplified by a parasitic lateral bipolar transition This model is based on analytic modeling, quasi-2-D simulation and experimental study of the maximum drain electric field in SOI, and a novel method for measuring the lateral BJT (bipolar junction transistor) current gain beta using GIDL (gate-induced drain leakage) current It can accurately model the breakdown voltage within 02 V for different channel lengths, gate voltages, and SOI film thicknesses >

An accurate model of thin film SOI-MOSFET breakdown voltage

Previous conflicting reports concerning fully-depleted SOI device hot electron reliability is partially due to misunderstanding over the maximum channel electric field (E/sub m/). Experimental results using SOI MOSFETs with body contacts indicate that E/sub m/ is just a weak function of thin-film SOI thickness (T/sub si/) and E/sub m/ can be significantly lower than in a bulk device with drain junction depth (X/sub j/) comparable to T/sub si/ The theoretical correlation between SOI MOSFET's gate current and substrate current are experimentally confirmed. This provides a means (I/sub G/) of studying E, in SOI device without body contacts. Both N- and P-MOSFETs can have better hot-carrier reliability than comparable bulk devices. Thin film SOI MOSFETs have better prospects for meeting breakdown voltage and hot-electron reliability requirements than previously thought. >

H.-J. Wann

Papers

Effects of N/sub 2/O anneal and reoxidation on thermal oxide characteristics

An accurate model of thin film SOI-MOSFET breakdown voltage

Characterization of hot-carrier effects in thin-film fully-depleted SOI MOSFETs

Characterization of hot-carrier effects in thin-film fully-depleted SOI MOSFETs