Stable Pad Conditioning Using Bundled Flexible Fibers in Chemical Mechanical Planarization

The bundled Flexible Fiber Conditioner (bundled FFC) was developed as a surface-conforming conditioning tool for chemical mechanical polishing (CMP). It leverages the bending behavior of individual fibers to maintain a consistent contact force of each fiber edge. By bundling the fibers together, excessive bending is restricted, allowing the fibers to interact with the pad with a small negative rake angle. Each fiber in the bundle acts independently, allowing uniform and efficient pad surface roughening. In the case of the bundled fibers, it becomes possible to stably roughen the pad even if the fiber tips wore and be rounded. As a result, stable conditioning performance and a longer lifespan can be expected regardless of the wear of the fiber tips. Contact ratio analysis further reveals that the roughened pad surface achieves fine and uniform contact across numerous points. In continuous operation tests, the bundled FFC demonstrated a high and stable material removal rate. The cutting rake angle at the fiber tip was estimated to be −7° degrees, based on the wear angle of the fiber end surface. These findings suggest that a small negative rake angle combined with a narrow cutting width is critical for effective pad surface roughening.