Robert Jérisian

Diffusion of low-dose implanted aluminum in silicon in inert and dry O2 ambient

Redistribution of a high-energy (3 MeV) low-dose (5×1013 cm−2) implanted aluminum profile in silicon under inert and dry O2 is investigated in the temperature range (900–1100 °C). The chemical profiles were measured by secondary ion mass spectroscopy and the effective diffusivities were extracted from the experimental data from fitting with calculated profiles obtained by numerical resolution of Fick’s law. It is found that the aluminum diffusion is significantly enhanced during thermal oxidation. The diffusivity enhancement decreases with the temperature. Comparison with boron data suggests that the mechanism of aluminum diffusion in silicon is similar to that of boron.

Lateral gettering of iron by cavities induced by helium implantation in silicon

Lateral gettering has been studied by introducing cavities in the periphery of large active devices. Cavities were induced by helium implantation followed by a thermal treatment on samples previously contaminated by iron. Those cavities are known to be efficient to trap metallic impurities in silicon by chemisorption. The iron distribution in samples of 6×6 mm2 area has been monitored by measuring current versus voltage characteristics and interstitial iron concentrations by deep level transient spectroscopy on Schottky diodes uniformly distributed. A symmetrical iron distribution has been observed with a decreasing concentration close to the gettering region. This lateral gettering is enhanced with increasing thermal budget. Extensions of several millimeters can be obtained allowing applications in power device technology.

Leakage current conduction in IrO2/PZT/Pt structures

Over the last few years, thin films of PbZrxTi1 − xO3 (PZT) have been the focus of extensive researches for high-k capacitor applications. However, we believe that the reliability properties and the degradation mechanisms of PZT capacitors need to be better understood. A good way to learn about failure mechanisms is to investigate the characteristics of leakage current conduction. In this paper we propose a model for current density evolution of IrO2/PZT/Pt structures as a function of time, voltage and temperature. The voltage and temperature evolution of leakage current is interpreted as an interface controlled thermoionic injection of carriers over a potential barrier at the cathode/PZT contact. The time evolution of the leakage current is mainly characterized by the resistance degradation phenomenon which results in a large increase in current density. A quantitative analytical model based on the redistribution of oxygen vacancies near the cathode interface has already been developed to account for this effect [1]. We propose a more complete model that also includes the role of oxygen vacancies on dielectric relaxation and trapping phenomena. The contributions of Pt and IrO2 electrodes on leakage current evolution are also discussed.

Gettering on Cavities Induced by Helium Implantation in Si: The Case of Boron

In this paper, we shed light on the strong interaction between the cavity layer induced by helium implantation and boron. First, we present the impact of the He gettering step on a boron-diffused profile. In order to study the boron-cavity interaction, we used uniformly boron-doped wafers implanted with a high dose of helium and annealed using conventional furnace annealing as well as rapid thermal annealing. Then, to avoid any precipitation phenomena, conditions were chosen such that the boron solid solubility value was not exceeded. Our experimental results indicate a large trapping of boron within the cavity layer that occurs at the early stage of the annealing. A quantitative study of the gettered dopant fraction has been performed. These results enable us to have a better understanding of this interaction of the He-gettering step with boron atoms, which are of great interest for device applications.

Impact of hydrogen implantation on helium implantation induced defects

Silicon-based power device performances are largely affected by metal contamination occurring during device manufacturing. Among the usual gettering techniques, recent developments were done on high dose helium implantation. Even though the gettering efficiency of this technique has been demonstrated in device application, the required doses are still extremely high for an industrial application. Recently, it has been shown that the use of H/He co-implantation limits the total requested doses [1]. In this paper, co-implantation of H/He, which has been already used to reduce the dose in the smart-cut® process is explored. The goal of this work is to decrease efficiently the implanted dose maintaining an efficient metallic gettering without degrading the Si surface. The impact of H implantation on He implantation induced defects is carefully studied. The TEM observations have evidenced that hydrogen addition drastically modified the defect band structure and promotes the cavity growth.. Additionally, we demonstrate that an efficient gettering can be obtained.

LIFETIME EXTRAPOLATION OF PZT CAPACITORS

ABSTRACT We propose a new methodology for lifetime determination of PZT capacitors, based on accelerated tests performed at low voltages and high temperatures. We believe that such a methodology is the only way to characterize the relevant failure mechanism for Time-Dependent Dielectric Breakdown of PZT capacitors. The capacitors lifetime at operating conditions is found to exceed 20 years.

Properties of Cavities Induced by Helium Implantation in Silicon and their Applications to Devices

He implantation at high dose, followed by a thermal annealing, is a n interesting technique for metallic impurity gettering in silicon. In this paper, we first in roduce the extended defects encountered after this gettering stage. Then, we will focus on both t he metallic and the dopant gettering by emphasizing the strong interaction between the defe ct layer induced by helium implantation and these impurities. We will demonstrate that there is no competition between metal and dopant gettering and we will try to compare the mechanisms invol ved. Our results enlighten the effect of the He gettering step on the dopant such as segregation and its partial deactivation in presence of He induced defects. Finally, we will present the i ns rtion and the impact of helium implantation gettering step on a bi-directional device, showing its high interest for device fabrication.

Lateral gettering of iron and platinum by cavities induced by helium implantation in silicon

Abstract The aim of this study is to characterize the lateral gettering of iron and platinum atoms by introducing cavities at the periphery of large active device areas. Cavities have been obtained by helium implantation ( 5×10 16 He + / cm 2 , 40 keV) followed by a thermal treatment on samples previously contaminated by iron and platinum. These cavities are known to be efficient in trapping metallic impurities in silicon by chemisorption. The wafers were annealed in the range of 800–1000°C for several minutes in a neutral ambience (N 2 ). The metallic distribution has been monitored in each active device area by using current versus voltage and deep level transient spectroscopy techniques (DLTS). A symmetrical distribution of metallic impurities and current values has been observed in each active region. The influence of cavities extends laterally to several millimeters depending on the temperature and time of diffusion. This lateral gettering effect is suitable for the purification of transverse power devices.

On the optimum thickness to test dielectric reliability, in an integrated technology of power devices

Abstract This paper deals with the extensive characterization of dielectric films with thicknesses from 20 to 65 nm. Thick dielectric reliability has been investigated with time dependent dielectric breakdown (TDDB). TDDB tests are conducted under constant current injection. Assuming that the logarithm of the median time-to-failure is described by a linear electric field dependence, a generalized empirical law for the long-term reliability of the dielectric is proposed. This law takes into account the applied electric field and the dielectric thickness. This reliability law is available for dielectric thicknesses greater than 10 nm. A procedure to test dielectrics of various thicknesses is given in order to predict their reliability in power integrated devices.

Trapping of aluminium by dislocation loops in Si

Abstract It has been shown that high-dose aluminium implantation leads to the formation of extended defects. The strong interaction between these defects and the dopant significantly affects the final profile. However, the detailed mechanisms governing the trapping on the defects are still unclear. The aim of this paper is to clarify the interaction of Al with extended defects. For this purpose, a well-defined band defect, created by a Ge amorphisation, was used independently of the aluminium implantation. The aluminium implantation conditions were chosen in order to obtain a buried Al marker layer located several micrometers beneath the surface, i.e. far away from the EOR band. The results of this investigation, reported in this contribution, evidence a clear accumulation of the dopant on the dislocation loops, indicating a direct trapping mechanism of the dopant.