During the ultra large scale integration(ULSI)process,the surface roughness of the polished silicon wafer plays an important role in the quality and rate of production of devices.In this work,the effects of oxidizer,surfactant,polyurethane pad and slurry additives on the surface roughness and topography of chemical-mechanical planarization(CMP)for silicon have been investigated.A standard atomic force microscopy(AFM)test method for the atomic scale smooth surface was proposed and used to measure the polished silicon surfaces.Finally,compared with the theoretical calculated Ra value of 0.0276 nm,a near-perfect silicon surface with the surface roughness at an atomic scale(0.5)was achieved based on an optimized CMP process.
LI JingLIU YuHongDAI YuanJingYUE DaChuanLU XinChunLUO JianBin
A finite element analysis(FEA)model is developed for the chemical-mechanical polishing(CMP)process on the basis of a 12-in five-zone polishing head.The proposed FEA model shows that the contact stress non-uniformity is less dependent on the material property of the membrane and the geometry of the retaining ring.The larger the elastic modulus of the pad,the larger contact stress non-uniformity of the wafer.The applied loads on retaining ring and zone of the polishing head significantly affect the contact stress distribution.The stress adjustment ability of a zone depends on its position.In particular,the inner-side zone has a high stress adjustment ability,whereas the outer-side zone has a low stress adjustment ability.The predicted results by the model are shown to be consistent with the experimental data.Analysis results have revealed some insights regarding the performance of the multi-zone CMP.
Nanoparticle movement near a surface is greatly influenced by electrostatic and Van der Waals forces between the particle and the surface,as well as by Brownian motion.In this paper,several precise equations are derived to describe the Van der Waals and electrostatic forces between a particle and a surface when the particle is removed from the surface.These include an equation for particle displacement under the electrostatic force,and a numerical calculation for particle displacement under the Van der Waals force.Finally,a kinematic model is constructed to describe the particle distribution under the effects of the electrostatic and Van der Waals forces,as well as the particle’s Brownian motion.The results show that increasing the multiply of the particle and surface zeta potential values and decreasing the ionic strength of the detergent can prevent a particle from redepositing onto a surface.
MEI HeGengZHAO DeWenWANG TongQinCHENG JieLU XinChun
