Applications
| Film Stress Principle Thin Film Deposition when a thin film is deposited onto a substrate like a wafer, it is usually done at elevated temperatures. After deposition, the substrate cools down to room temperature. The differences in thermal expansion coefficients between the film and the substrate causes mechanical stress. This effect and the intrinsic film stress may cause the wafer to bow as well as induce cracks, voids, hillock formation and film lifting, yield loss and poor reliability issues. |
| Measurement Principle FSM pioneered in the laser scanning technique for stress measurements. Film Stress measurement is based on Stoney's Equation, where the change of radius of curvature for the wafer is measured by a laser scanner. This is done in 2 steps. Typically, a bare wafer is prescanned ( First Scan ) followed by Film deposition, The wafer is remeasured in a postscan ( 2nd scan ). The radius of curvature change is then calculated |
Types of Film Stress Tools
|
| Applications FSM provides tools to measure wafer topography with 2D and 3D maps, before and after thin film deposition to characterize film stresses. FSM provides tools to measure wafer topography from room temperature to 1100 C, under vacuum, to characterize stress hysteresis, and materials desorption at elevated temperatures. |