Simulation Investigation On Reliability Of Interconnection Of GaN Based Chips

As one of the third generation semiconductor materials,GaN has been paid much attention due to its excellent performance.And GaN based chips are often work under high voltage,large current and high temperature,which can easily cause losing efficacy of interconnection.This paper based on theory of losing efficacy,simulations made on interconnection of GaN based chips to explore how the electromigration and thermal stress cause losing efficacy,the aim is to deal with the problem of reliability which was brought by the smal er and smaller size of chips.The simulation works of this paper contains electromigration simulation and thermal stress simulation.The former is simulation on different structure of interconnection,and made analysis on the distribution of current density and concentration of vacancy.And the latter is simulation on changing temperature,and made analysis on the hydrostatic stress and Mises stress.Here are details:Electromigration simulation of via of interconnection was made by Sentaurus TCAD.Different via structures such as different via diameters,vias with chamfer,slope vias and double vias were simulated under the same current source.The result shows that increasing via diameter has the lowest efficiency of reducing current density.The others are more efficient,and can enforce the anti-electromigration ability.And the concentration of vacancy is only determined by the diameter of bottom of via.The larger the diameter,the smal er the concentration.The thermal stress simulation was made by Abaqus.For three materials of dielectric layer:SiO₂,SiLK and CDO,SiLK and CDO are Low-k materials,they have higher CTE than Au,so when the temperature comes down,there are some compressive stress in the interconnection,and it causes higher stress gradient,so the interconnection is more easily losing efficacy due to the voids caused by high stress gradient.And for three materials of dielectric barrier:SiN,SiC and SiCOH,the former two materials has almost the same performance parameters,but SiCOH has smaller Young's modulus and larger CTE,this material is more easily deformed when temperature comes down,and the stress gradient gets larger,so it could lose efficacy due to the voids caused by high stress gradient.And in the simulation of structure,the simulation result turns out that the chamfer and slope via has little effect on the distribution of stress in interconnection no mater hydrostatic stress or Mises stress,the two structures has little effect on thermal stress of interconnection.The research about span of temperature shows that the reliability of interconnection declines with the span gets wilder.