Study On The Anisotropic Of Micro-nano Ag Interconnects During Sintering With Electric Field Assisted

With the rapid development of integrated circuit technology,the production of microelectronic devices has more and more requirements about the technology of graphics transfer technology.As a high-resolution,high-output,low-cost graphics transfer technology,nanoimprint technology has a great prospect for application.Nanoimprint technology based on pseudoplastic metal fluid can be used to fabricate silver interconnects,which is poorly conductive after imprint due to the existence of residual solvent between silver nanoparticles and numerous micro pores.Hence,sintering process is necessary to make silver microwires more compact.However,the width of interconnects as a key technological parameter can be influenced by the isotropic shrinkage of silver microwires after sintering.In this paper,electrostatic field and alternating electric field are applied during sintering of silver microwires to achieve a better shrinkage effect,such as higher shrinkage rate,lower resistivity and larger grain size.In the experiment of electrostatic field-assisted sintering,five electric field intensity gradients of 0 V/cm,200 V/cm,400 V/cm,600 V/cm and 800 V/cm are set.The experimental data include SEM and AFM images are analyzed,the results show that with the electric field intensity of 800 V/cm,the shrinkage effect is best.In this condition,the shrinkage rate increases about 2.4%,and the resistivity reduces from 2.94×10^-8?m to 2.07×10^-8?m,meanwhile the grain size increases from 53 nm to 113 nm compared with normal sintering.Moreover,the shrinkage model of silver microwires with the electrostatic field assisted during sintering is proposed based on nonlinear fitting of experimental data,hot press sintering,atomic flux diffusion and conservation of mass theory.Due to the existence of the stress gradient region in silver microwires caused by imprint process,part of particles in the electrostatic field can't contact with each other,which can cause a negative influence on the particle growth during whole heating process.Therefore,pore structures can still be observed in the SEM image of the silver microwires after sintering with electrostatic field assisted.Consequently,the alternating electric field is applied to assist sintering considering the"tamping effect"of the alternating electric field can act on the particles.In this experiment,periods of T=15 min,T=30 min and T=45 min are set as the alternating electric field experimental group.There are four different duty ratios in each experimental group.And the electrostatic field of the same electric field intensity is set as control group.The shrinkage rate,conductivity,and the SEM images are used to judge the particle growth and sintering effect.The experimental data show that the sintering effect of the silver microwires in the alternating electric field of any period and duty ratio is better than that in the electrostatic field.And the optimal sintering effect is obtained under the alternating electric field period of T=30 min and duty ratio of 4:1.Compared with the results obtained in the electrostatic field,the shrinkage rate of the silver microwires increases 1.864%,the resistivity of silver microwires reduces to15.3%.Besides,and the grain size of silver microwires turns out to improve 40.2%.It is also found from the SEM images that the pore structures are less,and the particles are closely arranged,besides the sintered neck area is bigger.