Effect of Co,Pd and Pt ultra-thin films on the Ni-silicide formation: investigating the sandwich configuration

The effect of Co, Pd and Pt ultrathin films on the kinetics of the formation of Ni-silicide by reactive diffusion is investigated. 50 nm Ni/1 nm X/ 50 nm Ni (X?=?Co, Pd, Pt) deposited on Si(100) substrates are studied using in-situ and ex-situ measurements by X-ray diffraction (XRD). The presence of Co, Pd or Pt thin films in between the Ni layers delays the formation of the metal rich phase compared to the pure Ni/Si system and thus these films act as diffusion barriers. A simultaneous silicide formation (δ-Ni₂Si and NiSi phases) different from the classic sequential formation is found during the consumption of the top Ni layer for which Ni has to diffuse through the barrier. A model for the simultaneous growth in the presence of a barrier is developed, and simulation of the kinetics measured by XRD is used to determine the permeability of the different barriers. Atom probe tomography (APT) of the Ni/Pd/Ni system shows that the Pd layer is located between the Ni top layer and δ-Ni₂Si during the silicide growth, in accordance with a silicide formation controlled by Ni diffusion through the Pd layer. The effect of the barrier on the silicide formation and properties is discussed.

     

Correction of secondary ion mass spectrometry profiles for atom diffusion measurements

A simple method is proposed in order to correct experimental secondary ion mass spectrometry (SIMS) profiles. This method uses only one parameter which is experimentally accessible. It is tested in the case of As SIMS profiles in Si(001) acquired with three different primary ion beam energies: 1, 3, and 9 keV. This method is shown to give consistent corrections. The correction of SIMS profiles measured in a same sample with different analysis conditions leads to the same As distribution.     

Arsenic and phosphorus codiffusion during silicon microelectronic processes

Arsenic (As) and phosphorus (P) implantations are concurrently used to create the n-zones of recent microelectronic device pn-junctions. We studied the As-P codiffusion effect on the junction depths during the dopant activation process. As diffusion is accelerated during codiffusion. The acceleration magnitude depends on As concentration and varies during annealing time. Contrasting with usual transient-enhanced-diffusion phenomena, a time delay can be observed before As diffusion acceleration occurs. P diffusion shows no specific modification due to codiffusion. Its diffusion behavior can be understood considering the usual Fermi level and electrical effects linked to the time evolution of the two dopant distributions. The behavior of As during codiffusion is discussed using finite element simulations.     

Evaluation of scanning capacitance microscopy sample preparation by focused ion beam

Due to the continuous reduction of the critical dimensions of semiconductor devices, it becomes very important to know the two dimensional (2D) doping profile for electrical performance of devices. Scanning Capacitance Microscopy (SCM) is a powerful technique for qualitative analysis of 2D doping species distribution, measuring small capacitance variations with high spatial resolution. For 2D carrier profiling, the region of interest must be accessible to the profiling instrument. SCM samples require cross-sectioning to expose the inner sample at a visible surface. In some analysis, the failure is localized at a very accurate address up to hundreds of nanometers. With the traditional polishing method of sample preparation it is very difficult to reach the exact location. For this reason we are investigating a new way to prepare SCM sample with Focused Ion Beam (FIB) and plasma etch in order to accurately choose the scanning zone. This paper presents a method to obtain SCM scans after a sample preparation by FIB and the influence of the FIB and the Plasma etcher on cross-sectioned SCM samples.     

Investigation of a new method for dopant characterization

In microelectronics, the size of the components is continuously decreasing and is now in deep submicron range. Therefore, the dimensions of the implant profile become a major issue. Indeed, a slight fluctuation of the profile could be the origin of detrimental effects of the final properties of the component, such as the increase of the leakage current for instance. The failure analysis at implant level makes it possible to solve problems which have occurred on the production line. It can explain bad properties of the component and consequently increase the reliability of the products manufactured. SCM (Scanning Capacitance Microscopy) and SSRM (Scanning Spreading Resistance Microscopy) are more and more used for dopant visualization. These techniques have some limitations for future devices, which are mainly the spatial resolution and the accessibility of the areas under investigation by the AFM electrical tip. The proposed approach combines chemical delineation and topographic AFM in order to take advantage of the accuracy of the topographic AFM profile measurement on implant delineated regions.