S. Favier

Critical thickness for plastic relaxation of SiGe on Si(001) revisited

We have revisited the critical thickness for plastic relaxation hc of SiGe on Si(001). To that end, we have started from prime 200-mm Si(001) wafers and grown (at 20 Torr with SiH2Cl2 and GeH4) various thickness and Ge content SiGe layers in an Epi Centura reduced-pressure–chemical-vapor-deposition chamber. Growth temperature was reduced from 700 °C to 550 °C, as the Ge content increased from 12% to 52%, to minimize surface roughening. X-ray diffraction (XRD) was performed on all samples to determine hc for the various Ge contents probed. Fully strained layers were characterized by: (i) peaks at a constant incidence angle that became narrower and more intense as the thickness increased, and (ii) the presence of numerous thickness fringes on each side of the layers’ peaks. Meanwhile, broader, less intense peaks (without thickness fringes) closer to the Si substrate peak were associated with plastically relaxed SiGe layers. Plastic strain relaxation was more gradual and less complete in higher Ge content la...

Critical Thickness Threshold in HfO2 Layers

Wet etch ability of HfO2 high k layers in diluted HF solutions is very attractive to achieve an efficient selective removal with respect to silicon consumption and metal gate compatibility for advanced technology node. Unfortunately in most cases HfO2 layers can not be etched in a wet mixture after the gate stack formation and dry etch. This behavior is now clearly correlated to the monoclinic crystalline phase [1;2]. This phase can be either an “as deposited” state in the case of high temperature deposition mode such as MOCVD, or a post integration state related to added thermal budget as for ALCVD. In this study, the HfO2 etch rate with a diluted HF/HCl chemical solution was tightly monitored as a function of both ALCVD and MOCVD deposition modes, under different annealing conditions and different deposited thicknesses.

Reduction of defect density on blanks: application to the extreme ultraviolet lithography

Abstract Our laboratory is involved in the French EUV (Extreme Ultra-Violet) program PREUVE to develop Mo/Si mirrors for blanks free of defects by using an ion beam sputtering deposition technique. This paper illustrates a reduction strategy used to lead to an EUV mirror with a defect density as low as possible. One of the methods adopted is the analysis of the process step by step, therefore, the defect number added by each process step has been quantified. It appears that the most critical step is substrate cleanness. Today, our best performance for a final mirror is 1.2 def/cm 2 with a defect size >200 nm. This value has been measured on our home-made counting device COMNET. Our counting device has been validated by comparison with a commercial tool. Two improvements have been implemented on COMNET to increase its routine performance which allows to detect particles of 200 nm. The first one is the sample illumination with a laser in oblique incidence (60°) which increases the signal-to-noise ratio. The noise is the roughness of the sample. The second one is the implementation of a cooled CCD camera with a variable exposure time. Thanks to these improvements, the detection of particles with a diameter size of 155 nm has been demonstrated. On the basis of the experimental results and calculations, the detection of 100 nm particles on silicon and EUV blanks can be reasonably predicted.

Contacts for monolithic 3D architecture: Study of Ni0.9Co0.1 silicide formation

In this work, we studied the solid-state reaction between a Ni0.9Co0.1 film and a silicon substrate. NiCo silicide is considered to substitute Ni- and NiPt-based silicides in 3D integration in order to extend the bottom transistor thermal stability. Thanks to the combined analysis of sheet resistance data, X-ray reflectivity spectra modelling, X-ray diffraction and wavelength dispersive X-ray fluorescence analyses on Ni0.9Co0.1/Si samples annealed at various temperatures, we were able to describe the phase sequence of the NiCo silicide formation.

Phase formation sequence in the Ti/InP system during thin film solid-state reactions

The metallurgical properties of the Ti/InP system meet a great interest for its use as a contact in the scope of various applications such as the Si Photonics. The investigations conducted on this system highlight the initiation of a reaction between the Ti and the InP substrate during the deposition process conducted at 100 °C. The simultaneous formation of two binary phases, namely, Ti2In5 and TiP, is attributed to the compositional gradient induced in the InP by the wet surface preparation and enhanced by the subsequent in situ Ar+ preclean. Once formed, the TiP layer acts as a diffusion barrier inhibiting further reaction up to 450 °C in spite of the presence of an important Ti reservoir. At higher temperature, however, i.e., from 550 °C, the reaction is enabled either by the enhancement of the species diffusion through the TiP layer or by its agglomeration. This reaction gives rise to the total consumption of the Ti2In5 and Ti while the TiP and In phases are promoted.

Laser Scattering: a Fast, Sensitive, In‐Line Technique for Advanced Process Development and Monitoring

Laser scattering on unpatterned wafers is a common technique, mainly used in semiconductor fabs for optical wafer inspection (i.e. defectivity). Previously, the low frequency part of the scattered light (called “haze”) was viewed mainly as a noise source that limits the particle detection sensitivity. However, the haze signal of KLA Tencor SP1 and SP2 tools contains enough information to improve in‐line surface characterization and to give, in less than one minute for a full‐wafer mapping, very encouraging results when running large metal contamination studies or when developing and monitoring, for example, SGOI, GeOI and silicides processes.

Evaluation of experimental techniques for In‐line Ion Implantation Characterization

This work presents an as exhaustive as possible review of methods which can be applied for in‐line monitoring of implant processes. The dynamic of each technique was evaluated for several typical applications. This review shows that methods which are sensitive to electrically active dopants with the presence of a PN junction (post annealing metrology only) are quite well correlated and show a 1 to 1 dynamic. Indirect methods which can be used either pre or/and post anneal are more case to case metrologies with dynamics changing with the characteristics of implant.

EUV mask blank: defect detection at 100 nm

The characteristics of a defect counting tool, COMNET< based on scattering light measurement, is presented. This prototype supports the development of defect-free EUV blanks. Thanks to new improvements, it becomes possible to detect PSL particles having a diameter as low as 100 nm, with a video CCD camera, on silicon substrates or on EUV blanks. To reach this sensitivity, one of the enhancements consists in a laser irradiation close to 65°. The present configuration and the use of a CCD camera, with a variable exposure time, should lead to the detection of 80 nm PSL particles deposited on silicon substrate. This extrapolation is based on experimental results and on a simple model. To detect 100 nm particle and smaller particles, it is essential to reduce the level of stray light and to increase the signal to noise ratio. In our application, the stray light essentially comes from three sources: the noise induced by the roughness of the sample, the Rayleigh scattering of the atmosphere, and the stray light in the room. The restrictions induced by these phenomena are described in some detail. All the improvements are not only available for the characterization of silicon substrates but also for transparent blank substrates and for EUV mask blanks. The additional noise induced by the tranparent substrate is analyzed. The defects, whatever the compoent sizes and the component shapes can be detected. A cross characterization achieved with a commercial tool on silicon substate is reported. Counting measurements performed on EUV blanks are shown. Furthermore, a more explicit definition of added defects is proposed.