Research On Electromigration Of Copper Interconnects And Tin Whisker Growth

Along with the development of microelectronics technology, the characteristic scale ofthe integrated circuit decreases constantly, and the cross-sectional area of VLSI interconnectmetal film of is becoming more and more small, and the under current density has increaseddramatically. At present, the metal interconnect electromigration has become one of the mainfailure mechanism of very large scale integrated circuit. In the development of the device tosub-micron size and nanometer, the width of the metal interconnect has been reduced, currentdensity increased, more prone to electromigration failure. Tin whisker growth, as one ofelectromigration failure, is the most serious damage to device, and more and more get theattention of people.This paper analyzed the electromigration failure form of copper interconnection line, anddesigned and fabricated experiment platform for electromigration test by means of measuringresistance through fourprobemethod which vacuum、temperature and current controlled.Surface interconnection line structure was proposed which can be used in electromigrationtest continuously——structure for test with fine interconnect and Diamond pattern connectedin turn. Then the structure was tested for electromigration, and after100hours,elcctromigration of cooper interconnection line with2um depth、20um width and1000lengthwas obtained. Structure for electromigration of TSV was put forward which was availabledirect measurement on one surface——Daisy chain structure which can be used to testcontinuously and current entrance, current export, positive voltage contact point and negativevoltage contact point was separated. Then the structure was tested for electromigration.General electromigration improve measures are put forward as well as improvement measuresagainst TSV electromigration.This paper also studied the tin whisker growth. Firstly,8different samples with differentmetal coatings, then4experiments was conducted to analyze the effect of different plating totin whisker growth position and tin whisker morphology, the influence of the surface coating layer to tin whisker growth, the electromigration of Cu-Sn layer and Cu-Sn alloy, and methodto control the diameter of tin whisker. It is concluded that tin whiskers of pure tincoatinggrowing on the surface of coating and many of these were slender, and that tinwhiskers of Cu-Sn layer growing on the edge of pattern and many of these were fasciculationor hill, and that to local surface with coating layer, tin whiskers can grow on where no coatinglayer and many of tin whiskers were kink shape，and that surface oxide layer promoted thegrowth of tin whisker and there was no whisker on pure tin coating which oxide layer hadbeen wiped out, and that electromigration of Cu-Sn layer and Cu-Sn alloy can happen underlow current Density, and that setting the aperture to close to the diameter of the tin whiskercan control the diameter of the tin whisker. Finely, micro structural of tin whisker was studiedand it was concluded that tin whisker surface was stripy.