Effect of Native Oxide on Polycrystalline Silicon CMP

The polycrystalline silicon Chemical Mechanical Polishing process is performed by using a hybrid chemical reaction and mechanical abrasion. A native oxide on the polysilicon surface was found to have affected the CMP results. This paper describes the effect of the native oxide on polysilicon CMP and the variation in the polishing characteristics with the concentration of the alkaline agent (potassium hydroxide, KOH). During CMP, the high-frequency friction force was simultaneously measured by using a CMP monitoring system to understand the polysilicon CMP characteristics. The result showed that the removal rate of polysilicon increased with the alkaline agent concentra- tion. However, the analyzed data from the CMP monitoring system showed that the initial friction signal had transition region during polysilicon polishing, resulting from the native oxide. To remove the native oxide on polysilicon, the authors performed a BOE (buffered oxide etch) treatment. After the native oxide on Polysilicon had been removed, the transition region was no longer found and higher material removal could be achieved. Consequently, we found that the removal of polysilicon was restricted by the native oxide, which was influenced by the alkaline agent. KCI Citation Count: 2