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Spinel wafers and methods of preparation

Image Number 5 for United States Patent #7919815.

Wafer suitable for semiconductor deposition application can be fabricated to have low bow, warp, total thickness variation, taper, and total indicated reading properties. The wafers can be fabricated by cutting a boule to produce rough-cut wafers, lapping the rough-cut wafers, etching the lapped wafers to remove a defect, deformation zone and relieve residual stress, and chemically mechanically polishing the etched wafers to desired finish properties. Etching can be performed by immersion in a heated etching solution comprising sulfuric acid or a mixture of sulfuric and phosphoric acids. A low pH slurry utilized in chemical mechanical polishing of the spinel wafer can comprise .alpha.-Al.sub.2O.sub.3 and an organic phosphate.

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