Bismuth Calcium Ferrite (Bi_0.9Ca_0.1FeO₃) Sputtering Targets

Empirical Determination of Z-Factor

Unfortunately, Z Factor and Shear Modulus are not readily available for many materials. In this case, the Z-Factor can also be determined empirically using the following method:

• Deposit material until Crystal Life is near 50%, or near the end of life, whichever is sooner.
• Place a new substrate adjacent to the used quartz sensor.
• Set QCM Density to the calibrated value; Tooling to 100%
• Zero thickness
• Deposit approximately 1000 to 5000 A of material on the substrate.
• Use a profilometer or interferometer to measure the actual substrate film thickness.
• Adjust the Z Factor of the instrument until the correct thickness reading is shown.

Another alternative is to change crystals frequently and ignore the error. The graph below shows the % Error in Rate/Thickness from using the wrong Z Factor. For a crystal with 90% life, the error is negligible for even large errors in the programmed versus actual Z Factor.