Custom-fabricated sapphire wafer carriers that are uniform, parallel, durable and impervious to solvents and etchants are available from Meller Optics Inc. They feature ±1.2-μm thickness and part-to-part uniformity, with parallelism to 10 arcsec, depending upon size, and they exhibit Moh 9 hardness that is second only to diamond. Suited for thinning semiconductor materials such as GaAs, they are available plain and can be perforated with custom patterns for hold-down or delamination. Able to withstand repeated use, they are chip-, chemical- and scratch-resistant. Custom-fabricated in 2- to 6-in.-diameter sizes as thin as 0.018 in., they can be supplied with flats, laser markings and other special characteristics. The carriers are priced according to size and configuration. Typically, there is a four- to six-week delivery period, according to the company.