Search

Abstract: Local stressors techniques are extensively used in CMOS technologies starting with the 90nm node to compensate the mobility loss induced by extensive scale down. The purpose is to generate some strain within the silicon channel to enhance carrier mobility. To achieve nMOS performance at the 45nm node, gate stressors are required in addition to standard nitride liners. With this option, the stress generated within the gate is directly transmitted into the channel and more than 10% gain in saturation current is achievable on nMOS. Stress is generated within the polysilicon gate through annealing under a capping liner. After liner removal, a part of this stress is memorized within the gate material. Final gate stress depends on both polysilicon pre-treatments and liner properties. This paper deals with material studies performed on capping liners in parallel to tests on electrical devices. Important parameters to generate stress under capping are presented. This allows providing a simple model and guidelines for further optimization. [Copyright &y& Elsevier]

Abstract: In this paper, the interaction observed in PMOS transistor between the boron lightly doped drain (LDD) extensions and the spacer oxide and nitride dielectrics have been studied, with a simple experimental methodology. Low thermal budget oxide obtained by sub-atmospheric chemical vapor deposition (SACVD) and nitride deposited by plasma process have been evaluated as spacer layers. The influence of the oxide liner hydrogen content is shown to be critical for the p type shallow junction. Indeed, during the activation anneal, hydrogen content increases the boron out diffusion from the extension into the oxide liner and yield to a significant dose loss in this area. Nitride porosity has also been studied. A lower boron dose loss is observed with a porous layer because hydrogen can degas out significantly from the oxide, during anneal, through the porous nitride film. These results confirm the model of boron out diffusion based on oxide hydrogen content proposed by Kohli. Finally, a boron diffusion mechanism driven by chemistry and enhanced by hydrogen defects is proposed. [Copyright &y& Elsevier]

Abstract: In the framework of the development of strained channel materials, the mechanical stress induced in silicon by a silicon nitride stressor layer is studied. The investigated samples are sub-micrometric periodic arrays of polysilicon lines deposited on thermally oxidised single crystal (001) Si substrate and capped with silicon nitride. We compare the stress induced in the silicon substrate by three layouts: without Si3N4, with a tensile Si3N4 or with a compressive Si3N4 layer on top of the poly lines. The periodic strain field in silicon is investigated by high resolution X-ray diffraction which is very sensitive to local strain (<10−4) and is non-destructive. The lines array induces a periodic strain field in silicon, which gives rise to distinct satellites in reciprocal space. The intensity of these satellites is related to the strain field in one cell. X-ray reciprocal space maps are measured on a 4 circles goniometer with a laboratory source. First experimental mappings around the symmetrical 004 Si Bragg peak are presented here. Elastic calculations are performed with a Finite Element Modelling code in order to extract the displacement field that is useful for structure factor calculations within kinematical approximation. The calculations are necessary for explaining the experimental reciprocal space maps intensity envelope and comparing the strain induced by the three investigated layouts. [Copyright &y& Elsevier]