Conducting all-in-one etch process for 3D-NAND fabrication requires close etch rate(E/R)for SiO2 and Si3N4;however,to attain comparable and high etch rate for both materials is challenging.In this work,we performed fi...Conducting all-in-one etch process for 3D-NAND fabrication requires close etch rate(E/R)for SiO2 and Si3N4;however,to attain comparable and high etch rate for both materials is challenging.In this work,we performed first-principle studies on the etching mechanism of Si3N4 in fluorocarbon/oxygen plasma.The feasibility of using fluorocarbon/oxygen plasma to etch Si3N4 while attaining close E/R to SiO2 through the complementary nitride to oxynitiride(SiOxNy)transformation has been identified.Such transformation involves two stages:N atom elimination and Si-O bond formation.By modeling the essential chemical reactions on the Si3N4 surface,we shed light upon the underlying mechanisms behind both stages.We simulated the N-elimination reactions involving the formation and desorption of NO and FNO molecules as well as the substitution with F atoms.We found that N atoms can be eliminated by forming NO molecules,especially with the assistance of F-substitution in Si-N bond breaking.The predicted O-additive energies indicates that forming SiOxNy structure after N-elimination is possible.Following that,the dependency of chemistries favoring either high E/R or active SiOxNy formation on the fluorocarbon/oxygen ratio was discussed.We hope that the work will build a foundation for future studies on pursuing all-in-one ON etch process via the surface modifications.展开更多
The continually increasing number of silicon oxide(SiO2)and nitride(Si3N4)layers in 3D-NAND offers both motivations and challenges for developing all-in-one plasma etch solutions for etching SiO2 and Si3N4 at a select...The continually increasing number of silicon oxide(SiO2)and nitride(Si3N4)layers in 3D-NAND offers both motivations and challenges for developing all-in-one plasma etch solutions for etching SiO2 and Si3N4 at a selectivity near unity while maintaining a high etch rate.This is essential for a simultaneous etch landing of all holes that differ in their respective SiO2 and Si3N4 layer numbers and dummy SiO2 thickness,and for a quick wafer turnover.Surface modification may be employed to make the SiO2 and Si3N4 layers closer in composition,either by converting Si3N4 to oxynitride(SiOxNy)[J.Micro.Manuf.1,20180102(2018)],or by converting SiO2 to SiOxNy,presented in this paper.We computationally demonstrate the feasibility of a nitridation-etch process for SiO2 in fluorocarbon/nitrogen-based plasma with molecular dynamics(MD)and quantum chemistry(QC)simulations.First,the nitridation via ion implantation is observed with MD,which replaces surface oxygen by nitrogen.Second,the reactions involving oxygen and silicon volatilization are energetically favorable per QC calculations.Finally,both MD and QC simulations indicate a synergy between fluorine and nitrogen etchants by enhancing each other’s reactivity with the SiO2 surface.These atomistic surface reaction mechanisms will offer insight for the development of robust engineering solutions for 3D-NAND fabrication.展开更多
文摘Conducting all-in-one etch process for 3D-NAND fabrication requires close etch rate(E/R)for SiO2 and Si3N4;however,to attain comparable and high etch rate for both materials is challenging.In this work,we performed first-principle studies on the etching mechanism of Si3N4 in fluorocarbon/oxygen plasma.The feasibility of using fluorocarbon/oxygen plasma to etch Si3N4 while attaining close E/R to SiO2 through the complementary nitride to oxynitiride(SiOxNy)transformation has been identified.Such transformation involves two stages:N atom elimination and Si-O bond formation.By modeling the essential chemical reactions on the Si3N4 surface,we shed light upon the underlying mechanisms behind both stages.We simulated the N-elimination reactions involving the formation and desorption of NO and FNO molecules as well as the substitution with F atoms.We found that N atoms can be eliminated by forming NO molecules,especially with the assistance of F-substitution in Si-N bond breaking.The predicted O-additive energies indicates that forming SiOxNy structure after N-elimination is possible.Following that,the dependency of chemistries favoring either high E/R or active SiOxNy formation on the fluorocarbon/oxygen ratio was discussed.We hope that the work will build a foundation for future studies on pursuing all-in-one ON etch process via the surface modifications.
文摘The continually increasing number of silicon oxide(SiO2)and nitride(Si3N4)layers in 3D-NAND offers both motivations and challenges for developing all-in-one plasma etch solutions for etching SiO2 and Si3N4 at a selectivity near unity while maintaining a high etch rate.This is essential for a simultaneous etch landing of all holes that differ in their respective SiO2 and Si3N4 layer numbers and dummy SiO2 thickness,and for a quick wafer turnover.Surface modification may be employed to make the SiO2 and Si3N4 layers closer in composition,either by converting Si3N4 to oxynitride(SiOxNy)[J.Micro.Manuf.1,20180102(2018)],or by converting SiO2 to SiOxNy,presented in this paper.We computationally demonstrate the feasibility of a nitridation-etch process for SiO2 in fluorocarbon/nitrogen-based plasma with molecular dynamics(MD)and quantum chemistry(QC)simulations.First,the nitridation via ion implantation is observed with MD,which replaces surface oxygen by nitrogen.Second,the reactions involving oxygen and silicon volatilization are energetically favorable per QC calculations.Finally,both MD and QC simulations indicate a synergy between fluorine and nitrogen etchants by enhancing each other’s reactivity with the SiO2 surface.These atomistic surface reaction mechanisms will offer insight for the development of robust engineering solutions for 3D-NAND fabrication.
