Investigation Of Plasma Chemistry In The Deposition Of F-doped SiCOH Films

In order to solve the problems caused by device-dimension continuous shrinking in ultmlarge-scale integrated chips,such as signal propagation delay,power consumption,and the cross-link between metal interconnects,porous ultralow dielectric constant(k＜2)SiCOH film have received close attention.The decrease of film density by introducing pores into film can reduce dielectric constant of SiCOH film effectively.If too many pores are introduced in the film,however,it will cause some problems such as bad mechanic property,the increase of hydrophilic property and contamination.To overcome these problems,a combination of weak polar bonds with lower density pores to prepare low-k materials has drawn attention.F doping SiCOH film is a kind of low-k material composed by weak polar Si-F bonds and Si-O cages.Due to the structure and properties of films depends on the intermediate gas phase in the plasma,the investigation on the plasma chemistry during the deposition of SiCOH film is one of the most important issues.This paper investigates the fragmentation behavior of decamethylcyclopentasiloxane(DMCPS)by electron impact and in electron cyclotron resonance plasma,and of CHF₃/DMCPS mixtures in ECR plasma using a quadrupole mass spectrometry,which is used as the precursors to deposit F-SiCOH film. Combined with the bonding configuration of F-SiCOH films,the relation between species in ECR plasma and films structures is analyzed.The results show that the main fragmentation behavior of DMCPS includes two stages.One is the broken of fivefold Si-O ring and then the formation of threefold Si-O ring and Si-O chain species.The other is the lost of hydrocarbon groups from Si atoms.In ECR discharge plasma,SiO tings crosslink with SiO chains and further form Si-O-Si cage structures.The cage structure is of advantage to the decreasing of film dielectric constant.For the CHF₃/DMCPS ECR plasma,some new radicals,such as SiF,SiF₃,SiFC₂H₂,occur except the SiO,CH_x(x=1,2,3)from the dissociation of DMCPS and the radicals from CHF₃ dissociation.Meanwhile,the weak polar bonds,such as SiF,CF,(CH₂)_n,form in the F-SiCOH film.The incorporation of these weak polar bonds into the film is of advantage to improving the problems,such as bad mechanic property.