Papers by Keyword: Buffing

Abstract: In chemical mechanical planarization (CMP) processes, ceria is generally used as the abrasive . After the CMP process, many ceria particles adhere to the wafer surface and must be removed prior to subsequent processing. In this study, the effect of varied viscosity was investigated during the buffing CMP process for ceria particle removal. After contaminating the wafer surface with ceria slurry, the ceria particles were removed through the buffing CMP process. The wafer surface was analyzed through inductively coupled plasma mass spectrometry (ICP-MS) to confirm cleaning efficiency. The ICP-MS data showed that, as buffing CMP solution viscosity increased, cleaning efficiency improved. These results suggest that increasing the viscosity of the buffing CMP solution improves its effectiveness in removing ceria particles.

Abstract: Viscoelastic polymer with high scratch resistance has been developed for coating material of product. Due to some particular characteristics such as viscoelasticity, it is difficult to finish the polymer coated surface. In the present circumstances, its polishing process is carried out by the trained technician and depends on the skill like adjustment of the polishing pressure according to the situation. To realize automation of the polishing, high-precision and highly-responsive force control is required firstly. Typically force control is done with force sensor. However when external sensor is used, there are some problems such as high-cost, reduction of machine stiffness and thermal drift. The thermal drift which is caused by polishing heat prohibits accurate measuring of force. The purpose of this research is to develop the polishing pressure control method without any additional sensor. In addition, applying the control method to buffing machine, buffing performance of viscoelastic polymer is experimentally analyzed.

Abstract: Viscoelastic polymers are used as one of coating materials for protecting the products from scratches. Presently, the repair of the coating surface for removing dust or extraneous matters has been performed through several polishing processes. However, it becomes increasingly difficult to polish its surface by only applying good skill and experience of skilled worker because a leading-edge viscoelastic polymer for coating is further scratch-resistant. Thus, based on quantitative evaluation of relation between polishing process and finished surface, it is necessary to make the polishing process appropriate for the leading-edge viscoelastic polymers. In this study, we attempt to establish the evaluation method of the polished surface and clarify the surface condition with invisible scratches.

Abstract: One of key processes in tungsten (W) CMP is to remove slurry particles inside W plug after CMP. In general, HF cleaning is well known to remove the slurry residue particles in W plugs. HF chemistry lifts off the particles by etching the plug during scrubbing and effectively removes particles. It is sometimes impossible to apply HF chemisty on W plug due to the degradation of electrical characteristics of a device. In this paper, a post W CMP cleaning process is proposed to remove residue particles without applying HF chemistry. After W CMP, recessed plugs are created, therefore they easily trap slurry particles during CMP process. These particles in recessed plug are not easy to remove by brush scrubbing when NH4OH chemistry is used for the cleaning because the brush surface can not reach the recessed area of plugs. Buffing with oxide slurry was followed by W CMP due to its high selectivity to W. The buffing polishes only oxide slightly which creates higher plug profiles than surrounding oxide. Higher profiles make the brush contact much more effectively and result in a similar particle removal efficiency even in NH4OH cleaning to that in HF brush scrubbing.