Study On The Effect Of Leveler And Heat Treatment On The Electrical Property Of The Damascene Electroplated Copper Films In Integrated Circuits

With the development of integrated circuit towards high speed,high density and high function,the characteristic dimensions of devices are shrinking,the copper interconnects of chips are becoming more and more thin and dense,and the interconnection delay caused by the too large capacitance resistance of copper interconnects is becoming more and more serious.The electrical property of metal interconnects has become an important factor in the development of integrated circuit.The resistance of copper interconnects is too high,on the one hand,it will increase the power consumption of integrated current,on the other hand,it will make the interconnection delay of integrated circuit more serious,moreover,reduce the reliability and then fail.In the advanced technology of electrodeposited copper interconnection,leveler and heat treatment are the key factors to prepare copper films with excellent electrical properties.In this paper,three kinds of levelers with different molecular structure were used to study the influence of levelers on the evolution of electrical resistance,micro-structure and impurity doping in the process of self-annealing of copper coating,and the internal mechanism of leveler affecting the electrical properties of the coating was explored.Secondly,five different temperatures are used for the heat treatment of electrodeposited copper films.By monitoring the evolution of electrical resistance,surface morphology and impurity distribution during the heat treatment,the mechanism of the influence of heat treatment temperature on the electrical properties of the copper films is studied,and the differences between heat treatment and self-annealing in optimizing the electrical properties of the copper films are compared.In this paper,it is found that the electrochemical inhibition ability of the three levelers is different in the electroplating solution,and the impurity content introduced into the copper films is also different.The former will affect the grain boundary energy density of copper films,which is an important driving force for self-annealing,and the latter will hinder the grain merging and growth in the process of self-annealing.The driving force of grain boundary and the hinder effect of impurities are two opposite factors,which work competitively for the self-annealing behavior and final electrical properties of the copper filmsIt is found that temperature is another important driving force for recrystallization of grains in copper films,which can significantly reduce the rate of reduction of electrical resistance and the time required for recrystallization.The optimization degree of heat treatment for electrical resistance does not increase with the increase of temperature,but takes 200℃as the critical point,showing a U-shaped rule,because too high temperature will intensify the reaction between the copper films and the barrier layer,thus reducing the reduction degree of electrical resistance.In addition,compared with the self-annealing,the grain size of the films after recrystallization is smaller and the impurity content of the films is higher because of the high speed of heat treatment.However,the electrical resistance of the films largely depends on the grain size and impurity content,so the optimization degree of heat treatment for the electrical properties of the films is less than that of self-annealing,and the advantage is more reflected in the time.