Research Of Low Temperature Interconnect Process Based On Copper Nanorods

With scaling down in size of electronic products and improvement of chip integration,the feature size in integrated circuit(IC)is approaching its physical limits.There are many technical bottlenecks in material,process,etc.The demands of high yield and performance and the challenges of power consumption and signal propagation delaying cannot be solved by traditional two-dimensional integrated technology.Three dimensional integrated technology has many advantages,such as reducing propagation delay,power consumption and noise,increasing bandwidth,decreasing the volume and weight,heterogeneous chip interconnection,and it is the most promising technical solution to these problem.This paper was focused on the preparation of copper nanorods,studying of low melting point characteristics and exploring a feasible low temperature bonding technique with copper nanorods.The main contents are as follows:(1)Preparation of copper nanorods.Copper nanorods were produced by an oblique angle deposition technique with magnetron sputtering or thermal evaporation.The difference in size and morphology of nanorods prepared by different devices were studied.Samples coated with copper nanorod layer were annealed an inert atmosphere,and a dense film with homogeneous structure was achieved at 500℃,substantially lower than its bulk melting point of 1085℃.The size of copper nanorods was reduced and array density was increased by exposure to the oxygen ambient periodically,and the melting point of nanorod was further decreased to 400℃.(2)Research of bonding based on nanorods.Samples coated with copper nanorod layer were applied to copper to copper bonding,and better bonding quality was achieved than samples without nanorods.Samples with thermal evaporating nanorods had best bonding quality.Sample pairs were applied to bonding in a vacuum,inert and reducing atmosphere respectively.The results showed that the lowest bonding temperatures of three kind samples achieved defect-free bonding layer decreased,and the strength bonded in same condition increased in sequence.Good bonding quality was achieved at 250~400℃,and the maximum strength was reach to 39.7MPa.The experiment verified the feasibility of copper to copper bonding with nanorod and its advantage.(3)Low temperature copper to copper bonding for three dimensional integration.We have studied the process of copper nanorod deposition on micro bump and succeeded in the deposition on 70μm micro bump array.The micro bump sample pairs with nanorods were bonded together and it presented a good bonding interface.Low temperature bonding for three dimensional integration was initially realized.In this paper,low temperature melting characteristic of copper nanorods were researched and nanorods were applied to bonding,guiding for low temperature copper to copper interconnection for three dimensional integration.