Mesures de contraintes par spectroscopie et imagerie Raman dans des dispositifs micro-électroniques

Stress measurements by Raman spectroscopy have been performed on microelectronic devices. Strain-induced effects on the Raman spectrum of silicon have been studied in order to set up the experimental work. Selection rules and instrumental parameters have been considered for backscattering experiments. Prior to the study of different microelectronic devices, the comparison of several Raman imaging techniques has been made. Shallow UV excitative wavelength has been found to be of extrem interest for spatial resolution improvement. A method based on simulations along with Raman experiments has been developed in order to measure stress in silicon. Accurate stress measurements have been performed using this method, including 3D Raman measurements on deep trench insulator. Silicon germanium alloys have also been studied by Raman spectroscopy, within the application field of the previous method.La spectroscopie Raman est utilisée dans le cadre de la caractérisation locale des contraintes mécaniques en microélectronique. Les effets des déformations sur le spectre Raman du silicium sont étudiés de manière à établir un protocole expérimental. Les notions importantes de résolution et d'observation sont abordées. Plusieurs techniques originales dérivées de la rétrodiffusion Raman sont mises en oeuvre. L'utilisation de l'ultraviolet proche permet d'améliorer considérablement la résolution spatiale des mesures Raman. Une méthode de mesure des contraintes basée sur le couplage entre simulations et expériences est développée. Différents dispositifs microélectroniques sont étudiés par cette méthode. Les résultats obtenus permettent de valider et d'étendre le champ d'application de la méthode. Des expériences de spectro-tomographie Raman sont réalisées sur des structures d'isolation. Enfin, une étude est menée sur des alliages silicium germanium

Mesures de contraintes par spectroscopie et imagerie Raman dans des dispositifs micro-électroniques

La spectroscopie Raman est utilisée dans le cadre de la caractérisation locale des contraintes mécaniques en microélectronique. Les effets des déformations sur le spectre Raman du silicium sont étudiés de manière à établir un protocole expérimental. Les notions importantes de résolution et d'observation sont abordées. Plusieurs techniques originales dérivées de la rétrodiffusion Raman sont mises en œuvre. L'utilisation de l'ultraviolet proche permet d'améliorer considérablement la résolution spatiale des mesures Raman. Une méthode de mesure des contraintes basée sur le couplage entre simulations et expériences est développée. Différents dispositifs microélectroniques sont étudiés par cette méthode. Les résultats obtenus permettent de valider et d'étendre le champ d'application de la méthode. Des expériences de spectro-tomographie Raman sont réalisées sur des structures d'isolation. Enfin, une étude est menée sur des alliages silicium germanium.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Local strain measurements in shallow trench insulator structures using near-ultraviolet Raman spectroscopy: Simulation and experiment

National audienceShallow trench insulator (STI) stress induced in active lines has been investigated both by near-ultraviolet (UV) Raman spectroscopy and mechanical modelization. Two different STI processes have been compared. The influence of the linewidth is also studied. After adjusting some instrumental and material parameters, all components of the stress tensors have been determined accurately. The polarization of the incoming light is discussed, showing that the selection rules are no longer respected at the edges of the STIs. Some of the limitations in spatial resolution of the Raman spectroscopy have been overcome, making use of the mechanical model and taking benefit from the higher spatial resolution of the UV excitation. In turn, the mechanical model has been refined from comparisons with experiments. It is therefore suggested that coupling these techniques may provide a relevant method to measure stress in the silicon for the integrated circuit industry. From a practical viewpoint, it is demonstrated that the use of the subatmospheric chemical vapor deposition process allows significant reduction of the compressive stress in the center of the active lines

Influence of gate leakage current on AlGaN/GaN HEMTs evidenced by low frequency noise and pulsed electrical measurements

International audienceThe study of the pulsed drain current or noise characteristics in AlGaN/GaN HEMTs is the key of knowledge for designing the power amplifiers, the low noise amplifiers and the oscillators or mixers, but it is well accepted today that this study is not fully accomplished without pointing on the effect of the gate leakage current; It is obvious that the transistor's leakage current may disturb its operation at high power and high frequency. Leakage currents studies are also an area of great importance in optimization of safe operating area and reliability of HEMTs. Therefore, room temperature pulsed I-V and low frequency noise measurements of gate and drain currents of AlGaN/GaN HEMTs have been investigated under different bias conditions on two devices showing identical drain current and different gate current levels. The results show a correlation between two non-destructive measurement techniques applied on devices under test

Ultra-thin strained SOI substrate analysis by pseudo-MOS measurements

International audiencePseudo-MOS (Ψ -MOSFET) measurements are a simple and rapid technique for an accurate evaluation of SOI wafer intrinsic electrical properties, prior to any CMOS processing. For the first time, we report Ψ -MOSFET measurements performed on Strained SOI (SSOI) wafers with ultra-thin silicon films (9.5 nm to 17.5 nm). To take into account the wafer specificities and the use of such thin conduction layers, adapted Ψ -MOSFET models and parameter extraction methods were necessary. The experiments show an increase of the threshold and flat band voltages and a mobility reduction as the strained film becomes thinner. Further electrical analyses, coupled with several morphological studies, do not reveal any relaxation of the strain in the thinnest films. The mobility is clearly enhanced in SSOI as compared with standard SOI substrates