The Technology Of Lapping And Polishing Copper By Fixed Abrasive CMP

Because it’s easy to adhere to the surface of the tool during the process of grinding or lapping,decreasing the space for chips, copper is regarded as a difficult-to-cut material. Fixed abrasivechemical mechanical polishing which has many advantages has become the research focus in the fieldof ultra-precision machining and lots of scholars have studied it. It has been used to machining opticalglass, IC chips, LED substrate materials and so on. In this paper, fixed abrasive pad was used torealizing the efficient lapping and rough polishing of copper. Then, conventional CMP was used forthe finishing polishing of copper to realizing its ultra-precision machining. The main works are asfollows:1. Cutting depth model of a single abrasive was established by mathematical modeling andtheoretically analyzed the influence factors of cutting depth. Through the combination of theory andexperiment, the suitable processing parameters of lapping copper were selected. During the process oflapping, the FAP with grooves on the surface had longer working life than the FAP with no grooves.The FAP which contains20~30μm abrasive had more serious glaze than the FAP which contains30~40μm abrasive, while the material removal rate was lower and the surface roughness was larger.With the increase of the lapping pressure, the material removal of FAP with30~40μm abrasiveincreased, the surface roughness decreased.2. The self-conditioning processing of hydrophilic FAP was realized. Two-factor experimentmethod was used to study the influence of resin matrix and porosity to the performance of machiningcopper, then the suitable resin matrix and porosity were selected and optimized the distribution ofpore. Material removal rate, friction coefficient, surface topography, and characteristic of chips wereobtained when lapping copper using different FAPs on different machining parameters. Resultsshowed that the FAP which only contains170#MgSO4particles and the one which contains the8#and500#MgSO4particles, with a mass fraction of10%and5%, were glazing to some extent during theprocess of lapping, while, the FAP which contains the8#and500#MgSO4particle, with a massfraction of5%and10%, displayed a good self-conditioning performance and its friction coefficientduring lapping was larger and keep steady. The material removal rate and the surface roughness oflapped surface were4.46μm/min and159nm respectively when using the later FAP at the flow rate of60ml/min.3. Optimized the alkaline slurry when roughly polishing copper by fixed abrasive pad. Results showed that, within the limits of concentration of test, with the increase of volume fraction ofhydrogen peroxide, the removal rate increased, while the surface roughness decreaseed;ethylenediamine could increase the removal rate greatly, meanwhile the surface roughness increased;BTA decreased the surface roughness, while the material removal rate also decreased. When thevolume fraction of hydrogen peroxide was5%, the volume fraction of tethylenediamine0.8%and themass fraction of BTA0.1%, the polishing effect was best, with a surface roughness of4.41nm, and amaterial removal rate of2.932μm/min.4. The process parameters of polishing copper by fixed abrasive pad were optimized. Theorthogonal experimental method was employed to optimize the influence of concentration of silica sol,polishing pressure, rotating speed, concentration of ethylenediamine for the material removal rate andsurface roughness. The material removal rate decreased with the increasing of concentration of silicasol, increased with increasing of polishing pressure and concentration of ethylenediamine, decreasedfirstly and then increased with the increasing of rotating speed. The surface roughness decreased withthe increasing of concentration of silica sol, polishing pressure and concentration of ethylenediamine,decreased firstly and then increased with the increasing of rotating speed. After comprehensiveoptimization of the surface roughness and the material removal rate, the best process parameters areconcentration of silica sol10%, polishing pressure20.7KPa, concentration of ethylenediamine1%,rotating speed70r/min, the material removal rate was89nm/min, the surface roughness was0.202nm.