ILD-CMP Wafer Edge Thickness Profile Stability Improvement via Acid Silicon Oxide Slurry Formulation Design

Acid silicon oxide slurry has many advantages in practical applications due to its low solid content, which provides good defect performance, better planarization efficiency, low cost and so on compared with traditional alkaline silicon oxide slurry. So far, it is being widely used in fab ILD CMP process all over the world. Since its low solid content, which is ∼70% less than that of alkaline silicon oxide slurry, the wafer edge (radius was 125mm∼150mm) thickness profile stability is difficult to control in ILD CMP process. ILD CMP post thickness profile is a key production index in the fab. In this research, the ILD CMP wafer edge profile stability was studied via adjusting acid silicon oxide slurry formulation. From the perspective of changing the distribution of slurry abrasive on the surface of polishing pad, the following two factors were mainly studied, namely slurry abrasive size and the amount of surface modifier of slurry abrasive. The results indicated that when abrasive size was ∼50nm and the amount of surface modifier was 1.2% (normalized), the thickness profile response show better linearity to pressure tuning, and the stability of the wafer edge thickness profile in the continuous process is greatly improved, with an increase of more than 95%.