The measurements described in this guide can significantly affect the function of the sapphire substrate.

Substrates with excessive form errors in the free state may cause processing errors in production.

The restrained state of the substrate is intended to simulate as closely as possible the form that the substrate will take in one of its intended uses. During processing, one surface of the substrate is sometimes forcibly restrained to a flat state through either vacuum or adhesion to a flat surface. The measurements in the clamped state are intended to model the form of the front surface of the substrate when the back surface is constrained to the reference plane. The form in the clamped state may have a direct impact on the performance of the substrate in use.

The user should determine whether the unrestrained or restrained measurements are most pertinent to the application and specify the appropriate parameters accordingly.

Knowledge of these characteristics can help the producer and consumer determine if the dimensional characteristics of a specimen substrate satisfy given geometrical requirements.

This guide is suitable for sapphire substrates in the as-sliced, lapped, polished, or other condition. Refer to SEMI M3 for substrate specifications.

Until the results of a planned interlaboratory evaluation of this guide are established, use of this guide for commercial transactions is not recommended unless the parties to the test establish the degree of correlation that can be obtained.