Tantalum And Niobium Silicides Formed By Scanning Electron Beam

Abstract

Tantalum and niobium silicides formed by Scanning Electron BeamZhang Guobing and Wang yangyuanDepartment of Computer Science and technology, Peking University Beijing. ChinaLin shi- Chang, Zhang yan sheng, Fan bing linInstitute of Electronics, Academia Sinica, Beijing, ChinaAbstractThe properties and structures of tantalum and niobium silicides formed by rapidannealing of scanning Electron Beam have been investigated. The fine layers of tantalum andsilicon Niobium and silicon were deposited by co- sputtering system and co- evaporatingsystem, respectively. The Scanning Electron beam Equipment with quasi -linear source wasused to realize the rapid annealing for forming the TaSi2 and NbSi2. The x -ray diffractionRBS and TEM have been used to characterize the Composition and structure of silicide film.The best conditions of forming silicides has been presented. The single phase TaSi2 andNbSi2 and the resistivity of 50 Micro Ohm -Cm have been obtained in annealing time of 10 -100seconds. The results have been compared with those of furnace thermal annealing.IntroductionThe refractory metal silicides have been playing an important role in the scaling downof integrated circuits to feature size of less than 2 um because of the low resistanceinterconnects and controlled metal -silicon interface reactions for both schottky and ohmiccontact.The bulk of the research to date has been Carried out in thermal equilibrium furnacereactions and both the film deposition and furnace annealing processes have been discussedin deteil along with characterized techniques in a lot of literatures.(1) The certain limi-tations have been found inAthe furnace thermal annealing because of longer time. In therecent years the rapid thermal annealing has been widely investigated. Laser(2), electronbeam(3), incoherent light(4) and ion beam mixing(5) have been used in this area. The mainfeatures offered by electron (and laser) beam processing are shorter reactin time localizedheat -treatment and rapid heating and cooling rates and thus, will minimize the dopantredistribution.Some results about metal silicon reaction induced by CW Scanned Laser and electron beamhave been reported (2) (3) (6) and these are related to the reactions of thin metal filimsdeposited by electron beam evaporation onto single crystal silicon substrates.In this paper, the properties and structures of tantalum and niobium silicides formedby scanning Electron Beam annealing have been investigated. The thin layers of tantalum andsilicon niobium and silicon are deposited by co- sputtering system and doulle E -beamevaporating system which are widely used in industry of integrated circuits, respectively.The uniform, essentially single phase silicides films are obtained with the scanned cwelectron beam. X -ray diffraction analysis Mev Ratherford backscattering spectrum andTransmission Electron Microscope have been utilized to characterize the structure of thefilms and the four probe equipment have been used to measure the electrical properties ofsilicide films. The results have been compared with those of furnace thermal annealing.ExperimentsThin layers of niobium and silicon were evaporated on silicon substrate using a doubleE -beam evaporation system (Type UMS -500 Balzers co.) with deposition rate = 3R /sec. in4 x 10-8 Torr pressure. During the evaporating the substrate temperature was keeped at108 °C. The thin layers of tantalum and silicon were also deposited on silicon wafers by Co-sputtering system (PERKIN ELMER 4450). The stochiometry and thickness of films weredetermined by Rutherford backscattering spectrum analysis. The total deposition filmthickness was found to be 2500X. The ratioes of silicon to niobium and silicon to tantalumwere found both to be 2.4.The Scanning Electron Beam (SEB) equipment was used to realize the rapid annealing toform niobium and tantalum silicides. The method of forming a quasi -linear source is tosynthesize a line by scanning a spot source with high speed