A pH-Controlled Chemical Mechanical Polishing Method for Thin Bonded Silicon-on-Insulator Wafers

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Abstract
A pH-controlled chemical mechanical polishing (CMP) method for fabricating largearea ultrathin silicon-on-insulator (SOI) layers with uniform thickness was developed. Using a polishing reagent with the pH and colloidal silica concentration lowered, together with grooves fabricated on the SOI layer to expose the insulating oxide, the polishing rate clearly decreased leaving a uniform 0.1-µ m-thick SOI layer. An SOI layer with superior thickness uniformity (±0.01 µ m) across 5-by-5-mm SOI-Si islands was obtained. The thickness uniformity across the wafers was decreased to ±0.07 µ m. In this technique, the end point for polishing was controlled to form thin SOI layers with uniform thickness.