Basic Research On Machining Technology Of Cu Surface Without Stress Flattening

Because copper has the advantages of low resistivity and strong anti-electromigration,it has been widely used as an interconnect material for integrated circuit.With the improvement of electronic technology,the attendant problem is that some defects such as residual stress and micro-cracks caused by the traditional chemical mechanical polishing process on the copper surface may affect the service performance of the electronic device.The experimental system of copper electrochemical polishing is established,and the influence of electrolyte formulation and experimental process parameters on the processing results is emphatically studied.Firstly,a copper electrochemical polishing experimental device is designed and built.The device includes the spindle servo feed system,electrolyte circulation filter system and electrolyte temperature control system,which can realize the rotation and longitudinal feed of the tool spindle,the electrolyte renewal,Temperature control and a variety of flow methods for electrochemical polishing experiments provide a good guarantee.Next,to find electrochemical polishing electrolyte optimal ratio of Cu,the following study was conducted.First of all,the electrolyte base fluid was selected.Through experimental analysis,55% phosphoric acid solution was determined as the electrolyte base fluid in phosphoric acid and HEDP.Then the electrolyte additive was studied.Ethylene glycol,sodium tripolyphosphate,benzotriazole,methylbenzotriazole,ascorbic acid,sodium citrate,oxalic acid,sodium gluconate and ethylene thiourea were screened by comparative experiment analysis methods.Finally,ascorbic acid and ethylene thiourea were selected as additives.Finally,the optimum process parameters were determined by the combination of single factor experiments and orthogonal experiments.The influence of process parameters and additives on the electrochemical polishing of copper was theoretically analyzed and studied.Under the condition that the material removal rate is as low as possible,the low surface roughness is obtained as the constraint conditions.The optimal process parameters for the electrochemical polishing of copper are voltage 10 V,duty cycle 23%,frequency 23 kHz,temperature 45 ?,processing time 14min;Solution ratio: 55% phosphoric acid,0.3% ascorbic acid,0.2% ethylene thiourea.The minimum surface roughness of the specimen obtained under this process parameter is 17 nm,and the material removal rate can reach below 500 nm / min.