Research On The Electroless Deposited NiRB(R=Cr/Co) Diffusion Barrier Layer For ULSI-Cu Metallization

Since 1997,IBM has released a copper wiring process for integrated circuit production,copper interconnection gradually gained predominance.But,with the continuous development of the integration and feature size,the size of device is smaller and smaller,the integration density is bigger and bigger,the working frequency is faster and faster.The challenges of copper interconnection are becoming increasingly prominent.Easy to diffusion and oxidation are critical problems of copper interconnection,so inserting a diffusion barrier layer between Cu and Si and adding a anti-oxidant layer on the surface of Cu has become hot spots of research.In this paper,the research was based on NiRB/Si(R=Cr/Co)diffusion barrier layer film for the sub 45 nm copper interconnection.The experimental parameters of electroless deposited NiRB(R=Cr/Co)thin films and Cu films were optimized,including the amount of chemical reagents,temperature and pH.NiRB/Si(R=Cr/Co)and NiRB/Cu/NiRB/Si(R=Cr/Co)samples were prepared and then annealed at temperatures ranging from 500 ? to 900 ?.The prepared samples were subjected to film thickness gauge,FPP,XRD,XPS and AFM to determine the thickness,sheet resistance,phases,elemental valence and surface morphology before and after annealing.The main contents and conclusions of the study are given as follows.1.Cu films,NiRB(R=Cr/Co)films and NiRB/Cu/NiRB/Si(R=Cr/Co)multilayer films were prepared by electroless deposition.The optimum experimental conditions for electroless deposited NiCrB film are as follows.The amount of chemical reagents were Na3C6H5O7·2H2O 40 g/l,NiSO4·6H2O 30 g/l,CrCl3·6H2O 12 g/l,DMAB 0.06 mol/l,CH3COONa·2H2O 25 g/l,NaF 6 g/l,NH4F 2.5 g/l,temperature was 85 ? pH was 11.The optimum experimental conditions for electroless deposited NiCoB film are as follows.The amount of chemical reagents were Na3C6H5O7·2H2O 41.17g/l C4H4O6KNa·4H2O 14.11 g/l,NiSO4·6H2O 28.91 g/l,CoSO4·7H2O 8.43 g/l,DMAB 0.04 mol/l,CH3COONa·2H2O 15 g/l,NaF 1.0 g/l,NH4F 2.5 g/l,temperature was 85 ?,pH was 11.The optimum experimental conditions for electroless deposited Cu film are as follows.The amount of chemical reagents were CuSO4·5H2O 20 g/l,EDTA-2Na 39 g/l,CHOCOOH·H2O 13.8 g/l C6H8O7·H2O 21 g/l,?-?' bipyridine(C10H8N2)10 mg/l,temperature was 77.5 ?,pH was 12.2.The electroless deposited NiCrB thin film was mainly composed of NiB and CrB2 compounds and elementary Ni.It had a low resistivity,strong adhesion and excellent oxidation resistance.Annealing experiment indicated that the failure temperature of the NiCrB barrier layer was 900 ? and the failure mechanism was crystallization and grain growth of the NiCrB barrier layer after high temperature annealing.This process caused Cu grains to reach Si substrate through the grain boundaries,and then the reaction between Cu and Si resulted in the formation of highly resistive Cu3Si.3.The electroless deposited NiCoB film was amorphous and it was mainly composed of CoB compound and elementary Ni It had a low resistivity and strong adhesion.Annealing experiment demonstrated that failure temperature of the NiCoB barrier film was 850 ?,the ratio of Ni to Si in Ni-Si compounds decreased with the increase of annealing temperature,orthorhombic Ni3Si2 and monoclinic Ni3Si transformed into cubic NiSi2 gradually,Cubic Cu diffused easily to Si-substrate through the grain boundaries of cubic NiSi2,and then reacted with Si and resulted in the formation of highly resistive Cu4Si.