Patent ID: 7749398

Claim:
A calibration wafer for determining an actual etch rate of an etchable material, the etchable material capable of redepositing onto the calibration wafer after being etched by a plasma from the calibration wafer, the calibration wafer comprising: a carrier substrate; a continuous first layer of a first material on the carrier substrate; and a patterned second layer of a second material on the first layer, the second layer comprising at least one discrete raised region of the second material bordering at least one discrete recessed region of the first material, wherein one of the first and second materials is the etchable material, the etchable material has a number of selective-redeposition sources defined by the at least one discrete raised region or by the at least one discrete recessed region, and a first amount of the etchable material is capable of being etched from each of the selective-redeposition sources upon etching by the plasma, wherein the number of selective-redeposition sources, a minimum separation distance between adjacent selective-redeposition sources, and a maximum surface area of each of the selective-redeposition sources are such that a second amount of the etchable material that is capable of being redeposited on each of the selective-redeposition sources, upon etching by the plasma, is less than about three percent of the first amount etched from each of the respective selective-redeposition sources.